From f7e27eb94b6c3c3bb1c9698d016d742967da3c61 Mon Sep 17 00:00:00 2001 From: Samantha McVey Date: Sat, 31 Dec 2016 15:27:27 -0800 Subject: Have perl6 highlight as perl6 now Also remove some trailing spaces. --- perl6.html.markdown | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'perl6.html.markdown') diff --git a/perl6.html.markdown b/perl6.html.markdown index 34ad70b7..defd1315 100644 --- a/perl6.html.markdown +++ b/perl6.html.markdown @@ -18,7 +18,7 @@ double paragraphs, and single notes. `#=>` represents the output of a command. -```perl +```perl6 # Single line comment start with a pound #`( @@ -813,7 +813,7 @@ die X::AdHoc.new(payload => 'Error!'); # Undefined values include: `Nil`, `Mu` and `Failure` as well as `Int`, `Str` # and other types that have not been initialized to any value yet. # You can check if something is defined or not using the defined method: -my $uninitialized; +my $uninitialized; say $uninitiazilzed.defined; #> False # When using `orelse` it will disarm the exception and alias $_ to that failure # This will avoid it being automatically handled and printing lots of scary @@ -1092,7 +1092,7 @@ say (1, 10, (20, 10) ).flat; #> (1 10 20 10) Now the iterable is flat # - `lazy` - Defer actual evaluation until value is fetched (forces lazy context) my @lazy-array = (1..100).lazy; -say @lazy-array.is-lazy; #> True # Check for lazyness with the `is-lazy` method. +say @lazy-array.is-lazy; #> True # Check for lazyness with the `is-lazy` method. say @lazy-array; #> [...] List has not been iterated on! my @lazy-array { .print }; # This works and will only do as much work as is # needed. -- cgit v1.2.3 From 7f0fff0adf38fb47b36da4a8c319c6c9c28c546d Mon Sep 17 00:00:00 2001 From: Samantha McVey Date: Mon, 6 Feb 2017 23:36:02 -0800 Subject: Fit some more things into 80 columns in the Perl 6 doc --- perl6.html.markdown | 38 ++++++++++++++++++++------------------ 1 file changed, 20 insertions(+), 18 deletions(-) (limited to 'perl6.html.markdown') diff --git a/perl6.html.markdown b/perl6.html.markdown index defd1315..e813978a 100644 --- a/perl6.html.markdown +++ b/perl6.html.markdown @@ -86,10 +86,10 @@ my %hash = key1 => 'value1', key2 => 'value2'; # same result as above # You can also use the "colon pair" syntax: # (especially handy for named parameters that you'll see later) -my %hash = :w(1), # equivalent to `w => 1` - # this is useful for the `True` shortcut: - :truey, # equivalent to `:truey(True)`, or `truey => True` - # and for the `False` one: +my %hash = :w(1), # equivalent to `w => 1` + # this is useful for the `True` shortcut: + :truey, # equivalent to `:truey(True)`, or `truey => True` + # and for the `False` one: :!falsey, # equivalent to `:falsey(False)`, or `falsey => False` ; @@ -125,8 +125,8 @@ hello-to; #=> Hello, World ! hello-to(); #=> Hello, World ! hello-to('You'); #=> Hello, You ! -## You can also, by using a syntax akin to the one of hashes (yay unified syntax !), -## pass *named* arguments to a `sub`. +## You can also, by using a syntax akin to the one of hashes +## (yay unified syntax !), pass *named* arguments to a `sub`. # They're optional, and will default to "Any". sub with-named($normal-arg, :$named) { say $normal-arg + $named; @@ -145,8 +145,8 @@ sub with-mandatory-named(:$str!) { say "$str !"; } with-mandatory-named(str => "My String"); #=> My String ! -with-mandatory-named; # run time error: "Required named parameter not passed" -with-mandatory-named(3); # run time error: "Too many positional parameters passed" +with-mandatory-named; # run time error: "Required named parameter not passed" +with-mandatory-named(3);# run time error:"Too many positional parameters passed" ## If a sub takes a named boolean argument ... sub takes-a-bool($name, :$bool) { @@ -169,9 +169,9 @@ my &s = &say-hello; my &other-s = sub { say "Anonymous function !" } # A sub can have a "slurpy" parameter, or "doesn't-matter-how-many" -sub as-many($head, *@rest) { # `*@` (slurpy) will basically "take everything else". - # Note: you can have parameters *before* (like here) - # a slurpy one, but not *after*. +sub as-many($head, *@rest) { #`*@` (slurpy) will "take everything else" +# Note: you can have parameters *before* a slurpy one (like here), +# but not *after*. say @rest.join(' / ') ~ " !"; } say as-many('Happy', 'Happy', 'Birthday'); #=> Happy / Birthday ! @@ -223,9 +223,9 @@ say $x; #=> 52 # - `if` # Before talking about `if`, we need to know which values are "Truthy" -# (represent True), and which are "Falsey" (or "Falsy") -- represent False. -# Only these values are Falsey: 0, (), {}, "", Nil, A type (like `Str` or `Int`), -# and of course False itself. +# (represent True), and which are "Falsey" (or "Falsy") -- represent False. +# Only these values are Falsey: 0, (), {}, "", Nil, A type (like `Str` or `Int`) +# and of course False itself. # Every other value is Truthy. if True { say "It's true !"; @@ -265,13 +265,14 @@ say $age > 18 ?? "You are an adult" !! "You are under 18"; given "foo bar" { say $_; #=> foo bar - when /foo/ { # Don't worry about smart matching yet – just know `when` uses it. + when /foo/ { # Don't worry about smart matching yet – just know `when` uses it # This is equivalent to `if $_ ~~ /foo/`. say "Yay !"; } - when $_.chars > 50 { # smart matching anything with True (`$a ~~ True`) is True, + when $_.chars > 50 { # smart matching anything with True is True, + # i.e. (`$a ~~ True`) # so you can also put "normal" conditionals. - # This when is equivalent to this `if`: + # This `when` is equivalent to this `if`: # if $_ ~~ ($_.chars > 50) {...} # Which means: # if $_.chars > 50 {...} @@ -288,7 +289,8 @@ given "foo bar" { # but can also be a C-style `for` loop: loop { say "This is an infinite loop !"; - last; # last breaks out of the loop, like the `break` keyword in other languages + last; # last breaks out of the loop, like the `break` keyword in other + # languages } loop (my $i = 0; $i < 5; $i++) { -- cgit v1.2.3 From 75abbf209e1e7c0c64f0cf5be862f93c82dfcb7b Mon Sep 17 00:00:00 2001 From: Cale Date: Mon, 27 Feb 2017 13:25:52 -0500 Subject: add much needed spacing with markdown headers (#2676) --- perl6.html.markdown | 173 +++++++++++++++++++++++++++++++++++++++------------- 1 file changed, 131 insertions(+), 42 deletions(-) (limited to 'perl6.html.markdown') diff --git a/perl6.html.markdown b/perl6.html.markdown index e813978a..7485ed57 100644 --- a/perl6.html.markdown +++ b/perl6.html.markdown @@ -25,14 +25,20 @@ double paragraphs, and single notes. Multiline comments use #` and a quoting construct. (), [], {}, 「」, etc, will work. ) +``` -### Variables +## Variables +```perl6 # In Perl 6, you declare a lexical variable using `my` my $variable; # Perl 6 has 4 kinds of variables: +``` -## * Scalars. They represent a single value. They start with a `$` +### Scalars + +```perl6 +# Scalars represent a single value. They start with a `$` my $str = 'String'; # double quotes allow for interpolation (which we'll see later): @@ -46,8 +52,12 @@ my $bool = True; # `True` and `False` are Perl 6's boolean values. my $inverse = !$bool; # You can invert a bool with the prefix `!` operator my $forced-bool = so $str; # And you can use the prefix `so` operator # which turns its operand into a Bool +``` -## * Lists. They represent multiple values. Their name start with `@`. +### Lists + +```perl6 +# Lists represent multiple values. Their name start with `@`. my @array = 'a', 'b', 'c'; # equivalent to : @@ -66,8 +76,11 @@ say "Interpolate all elements of an array using [] : @array[]"; my @keys = 0, 2; @array[@keys] = @letters; # Assignment using an array containing index values say @array; #=> a 6 b +``` -## * Hashes, or key-value Pairs. +### Hashes, or key-value Pairs. + +```perl6 # Hashes are pairs of keys and values. # You can construct a Pair object using the syntax `Key => Value`. # Hash tables are very fast for lookup, and are stored unordered. @@ -96,9 +109,13 @@ my %hash = :w(1), # equivalent to `w => 1` say %hash{'key1'}; # You can use {} to get the value from a key say %hash; # If it's a string, you can actually use <> # (`{key1}` doesn't work, as Perl6 doesn't have barewords) +``` -## * Subs: subroutines or functions as most other languages call them are -# created with the `sub` keyword. +## Subs + +```perl6 +# subroutines or functions as most other languages call them are +# created with the `sub` keyword. sub say-hello { say "Hello, world" } sub say-hello-to(Str $name) { # You can provide the type of an argument @@ -186,8 +203,11 @@ sub concat3($a, $b, $c) { } concat3(|@array); #=> a, b, c # `@array` got "flattened" as a part of the argument list +``` -### Containers +## Containers + +```perl6 # In Perl 6, values are actually stored in "containers". # The assignment operator asks the container on the left to store the value on # its right. When passed around, containers are marked as immutable. @@ -216,11 +236,12 @@ sub x-store() is rw { $x } x-store() = 52; # in this case, the parentheses are mandatory # (else Perl 6 thinks `x-store` is an identifier) say $x; #=> 52 +``` +## Control Flow Structures +### Conditionals -### Control Flow Structures -## Conditionals - +```perl6 # - `if` # Before talking about `if`, we need to know which values are "Truthy" # (represent True), and which are "Falsey" (or "Falsy") -- represent False. @@ -249,7 +270,11 @@ say "Quite truthy" if True; my $age = 30; say $age > 18 ?? "You are an adult" !! "You are under 18"; +``` +### given/when, or switch + +```perl6 # - `given`-`when` looks like other languages' `switch`, but is much more # powerful thanks to smart matching and Perl 6's "topic variable", $_. # @@ -282,9 +307,11 @@ given "foo bar" { say "Something else" } } +``` -## Looping constructs +### Looping constructs +```perl6 # - `loop` is an infinite loop if you don't pass it arguments, # but can also be a C-style `for` loop: loop { @@ -327,9 +354,11 @@ for @array { if long-computation() -> $result { say "The result is $result"; } +``` -### Operators +## Operators +```perl6 ## Since Perl languages are very much operator-based languages, ## Perl 6 operators are actually just funny-looking subroutines, in syntactic ## categories, like infix:<+> (addition) or prefix: (bool not). @@ -448,12 +477,18 @@ $b || $a; # 1 $a *= 2; # multiply and assignment. Equivalent to $a = $a * 2; $b %%= 5; # divisible by and assignment @array .= sort; # calls the `sort` method and assigns the result back +``` + +## More on subs ! -### More on subs ! +```perl6 # As we said before, Perl 6 has *really* powerful subs. We're going to see # a few more key concepts that make them better than in any other language :-). +``` + +### Unpacking ! -## Unpacking ! +```perl6 # It's the ability to "extract" arrays and keys (AKA "destructuring"). # It'll work in `my`s and in parameter lists. my ($f, $g) = 1, 2; @@ -521,7 +556,11 @@ sub list-of($n) { } } my @list3 = list-of(3); #=> (0, 1, 2) +``` + +### lambdas +```perl6 ## You can create a lambda with `-> {}` ("pointy block") or `{}` ("block") my &lambda = -> $argument { "The argument passed to this lambda is $argument" } # `-> {}` and `{}` are pretty much the same thing, except that the former can @@ -564,8 +603,11 @@ map(sub ($a, $b) { $a + $b + 3 }, @array); # (here with `sub`) # Note : those are sorted lexicographically. # `{ $^b / $^a }` is like `-> $a, $b { $b / $a }` +``` + +### About types... -## About types... +```perl6 # Perl6 is gradually typed. This means you can specify the type # of your variables/arguments/return types, or you can omit them # and they'll default to "Any". @@ -579,8 +621,11 @@ map(sub ($a, $b) { $a + $b + 3 }, @array); # (here with `sub`) # You can specify the type you're subtyping (by default, Any), # and add additional checks with the "where" keyword: subset VeryBigInteger of Int where * > 500; +``` + +### Multiple Dispatch -## Multiple Dispatch +```perl6 # Perl 6 can decide which variant of a `sub` to call based on the type of the # arguments, or on arbitrary preconditions, like with a type or a `where`: @@ -624,9 +669,11 @@ multi with-or-without-you { # sub trait_mod:(Routine $r, :$rw!) {} # # (commented because running this would be a terrible idea !) +``` +## Scoping -### Scoping +```perl6 # In Perl 6, unlike many scripting languages, (such as Python, Ruby, PHP), # you must declare your variables before using them. The `my` declarator # you have learned uses "lexical scoping". There are a few other declarators, @@ -646,9 +693,11 @@ outer()(); #=> 'Foo Bar' # As you can see, `$file_scoped` and `$outer_scoped` were captured. # But if we were to try and use `$bar` outside of `foo`, # the variable would be undefined (and you'd get a compile time error). +``` -### Twigils +## Twigils +```perl6 # There are many special `twigils` (composed sigil's) in Perl 6. # Twigils define the variables' scope. # The * and ? twigils work on standard variables: @@ -683,9 +732,11 @@ call_say_dyn(); #=> 25 100 # we are calling it from outside. say_dyn(); #=> 1 100 We changed the value of $*dyn_scoped_2 in call_say_dyn # so now its value has changed. +``` -### Object Model +## Object Model +```perl6 # To call a method on an object, add a dot followed by the method name: # => $object.method # Classes are declared with the `class` keyword. Attributes are declared @@ -730,8 +781,11 @@ say $class-obj.get-value; #=> 15 #$class-obj.attrib = 5; # This fails, because the `has $.attrib` is immutable $class-obj.other-attrib = 10; # This, however, works, because the public # attribute is mutable (`rw`). +``` + +### Object Inheritance -## Object Inheritance +```perl6 # Perl 6 also has inheritance (along with multiple inheritance) # While `method`'s are inherited, `submethod`'s are not. # Submethods are useful for object construction and destruction tasks, @@ -768,9 +822,12 @@ $Madison.talk; # prints "Goo goo ga ga" due to the overrided method. # `$a .= b` is the same as `$a = $a.b`) # Also note that `BUILD` (the method called inside `new`) # will set parent properties too, so you can pass `val => 5`. +``` +### Roles, or Mixins -## Roles are supported too (also called Mixins in other languages) +```perl6 +# Roles are supported too (also called Mixins in other languages) role PrintableVal { has $!counter = 0; method print { @@ -798,8 +855,11 @@ class Item does PrintableVal { # NOTE: You can use a role as a class (with `is ROLE`). In this case, methods # will be shadowed, since the compiler will consider `ROLE` to be a class. } +``` + +## Exceptions -### Exceptions +```perl6 # Exceptions are built on top of classes, in the package `X` (like `X::IO`). # In Perl6 exceptions are automatically 'thrown' open 'foo'; #> Failed to open file foo: no such file or directory @@ -828,8 +888,11 @@ open 'foo' orelse say "Something happened $_"; #> Something happened # Both of those above work but in case we get an object from the left side that # is not a failure we will probably get a warning. We see below how we can use # `try` and `CATCH` to be more specific with the exceptions we catch. +``` + +### Using `try` and `CATCH` -## Using `try` and `CATCH` +```perl6 # By using `try` and `CATCH` you can contain and handle exceptions without # disrupting the rest of the program. `try` will set the last exception to # the special variable `$!` Note: This has no relation to $!variables. @@ -883,8 +946,11 @@ try { # Those are "good" exceptions, which happen when you change your program's flow, # using operators like `return`, `next` or `last`. # You can "catch" those with `CONTROL` (not 100% working in Rakudo yet). +``` + +## Packages -### Packages +```perl6 # Packages are a way to reuse code. Packages are like "namespaces", and any # element of the six model (`module`, `role`, `class`, `grammar`, `subset` # and `enum`) are actually packages. (Packages are the lowest common denominator) @@ -915,8 +981,11 @@ grammar Parse::Text::Grammar { # A grammar is a package, which you could `use` my $actions = JSON::Tiny::Actions.new; # We'll see how to export variables and subs in the next part: +``` + +## Declarators -### Declarators +```perl6 # In Perl 6, you get different behaviors based on how you declare a variable. # You've already seen `my` and `has`, we'll now explore the others. @@ -978,10 +1047,11 @@ for ^5 -> $a { # Next iteration will re-run `rand`. } } +``` +## Phasers - -### Phasers +```perl6 # Phasers in Perl 6 are blocks that happen at determined points of time in your # program. They are called phasers because they mark a change in the phase # of a program. For example, when the program is compiled, a for loop runs, @@ -1041,8 +1111,11 @@ sub do-db-stuff { KEEP $db.commit; # commit the transaction if all went well UNDO $db.rollback; # or rollback if all hell broke loose } +``` + +## Statement prefixes -### Statement prefixes +```perl6 # Those act a bit like phasers: they affect the behavior of the following code. # Though, they run in-line with the executable code, so they're in lowercase. # (`try` and `start` are theoretically in that list, but explained somewhere else) @@ -1085,8 +1158,11 @@ say join ',', gather if False { constant thrice = gather for ^3 { say take $_ }; # Doesn't print anything # versus: constant thrice = eager gather for ^3 { say take $_ }; #=> 0 1 2 +``` + +## Iterables -### Iterables +```perl6 # Iterables are objects that can be iterated similar to the `for` construct # `flat`, flattens iterables: say (1, 10, (20, 10) ); #> (1 10 (20 10)) Notice how grouping is maintained @@ -1108,9 +1184,11 @@ quietly { warn 'This is a warning!' }; #=> No output # - `contend` - Attempts side effects under STM # Not yet implemented ! +``` -### More operators thingies ! +## More operators thingies ! +```perl6 ## Everybody loves operators ! Let's get more of them # The precedence list can be found here: @@ -1128,8 +1206,11 @@ $a ! $b ! $c; # with a list-associative `!`, this is `infix:<>` !$a! # with left-associative `!`, this is `(!$a)!` !$a! # with right-associative `!`, this is `!($a!)` !$a! # with non-associative `!`, this is illegal +``` -## Create your own operators ! +### Create your own operators ! + +```perl6 # Okay, you've been reading all of that, so I guess I should try # to show you something exciting. # I'll tell you a little secret (or not-so-secret): @@ -1193,8 +1274,11 @@ postcircumfix:<{ }>(%h, $key, :delete); # (you can call operators like that) # (you are, obviously, recommended against making an operator out of # *everything* -- with great power comes great responsibility) +``` -## Meta operators ! +### Meta operators ! + +```perl6 # Oh boy, get ready. Get ready, because we're delving deep # into the rabbit's hole, and you probably won't want to go # back to other languages after reading that. @@ -1281,8 +1365,11 @@ say @fib[^10]; #=> 1 1 2 3 5 8 13 21 34 55 # Note : as for ranges, once reified, elements aren't re-calculated. # That's why `@primes[^100]` will take a long time the first time you print # it, then be instant. +``` -### Regular Expressions +## Regular Expressions + +```perl6 # I'm sure a lot of you have been waiting for this one. # Well, now that you know a good deal of Perl 6 already, we can get started. # First off, you'll have to forget about "PCRE regexps" (perl-compatible regexps). @@ -1402,8 +1489,11 @@ so 'foo' ~~ / <-[ f o ]> + /; # False so 'foo' ~~ / <[ a..z ] - [ f o ]> + /; # False (any letter except f and o) so 'foo' ~~ / <-[ a..z ] + [ f o ]> + /; # True (no letter except f and o) so 'foo!' ~~ / <-[ a..z ] + [ f o ]> + /; # True (the + doesn't replace the left part) +``` -## Grouping and capturing +### Grouping and capturing + +```perl6 # Group: you can group parts of your regexp with `[]`. # These groups are *not* captured (like PCRE's `(?:)`). so 'abc' ~~ / a [ b ] c /; # `True`. The grouping does pretty much nothing @@ -1478,7 +1568,7 @@ so 'ayc' ~~ / a [ b | y ] c /; # `True`. Obviously enough ... # and other things that can't traditionnaly be represented by normal regexps. # # Then, all the alternatives are tried at once, and the longest wins. -# Exemples: +# Examples: # DECLARATIVE | PROCEDURAL / 'foo' \d+ [ || ] /; # DECLARATIVE (nested groups are not a problem) @@ -1489,11 +1579,11 @@ so 'ayc' ~~ / a [ b | y ] c /; # `True`. Obviously enough ... # Note: the first-matching `or` still exists, but is now spelled `||` 'foo' ~~ / fo || foo /; # `fo` now. +``` +## Extra: the MAIN subroutine - - -### Extra: the MAIN subroutine +```perl6 # The `MAIN` subroutine is called when you run a Perl 6 file directly. # It's very powerful, because Perl 6 actually parses the arguments # and pass them as such to the sub. It also handles named argument (`--foo`) @@ -1521,13 +1611,12 @@ multi MAIN('import', File, Str :$as) { ... } # omitting parameter name # As you can see, this is *very* powerful. # It even went as far as to show inline the constants. # (the type is only displayed if the argument is `$`/is named) +``` -### -### APPENDIX A: -### +## APPENDIX A: ### List of things -### +```perl6 # It's considered by now you know the Perl6 basics. # This section is just here to list some common operations, # but which are not in the "main part" of the tutorial to bloat it up -- cgit v1.2.3 From ae9762fd13dc75113a8d64091181477510825819 Mon Sep 17 00:00:00 2001 From: ven Date: Thu, 25 May 2017 14:56:49 +0200 Subject: Update perl6.html.markdown --- perl6.html.markdown | 35 +++++++++++++++++++++++------------ 1 file changed, 23 insertions(+), 12 deletions(-) (limited to 'perl6.html.markdown') diff --git a/perl6.html.markdown b/perl6.html.markdown index 7485ed57..ee94f5bf 100644 --- a/perl6.html.markdown +++ b/perl6.html.markdown @@ -440,6 +440,7 @@ say @array[^10]; # you can pass arrays as subscripts and it'll return # Note : when reading an infinite list, Perl 6 will "reify" the elements # it needs, then keep them in memory. They won't be calculated more than once. # It also will never calculate more elements that are needed. +# Trying # An array subscript can also be a closure. # It'll be called with the length as the argument @@ -961,10 +962,9 @@ try { use JSON::Tiny; # if you installed Rakudo* or Panda, you'll have this module say from-json('[1]').perl; #=> [1] -# Declare your own packages like this: -# `class Package::Name::Here;` to declare a class, or if you only want to -# export variables/subs, you can use `module`. If you're coming from Perl 5 -# please note you're not usually supposed to use the `package` keyword. +# You should not declare packages using the `package` keyword (unlike Perl 5). +# Instead, use `class Package::Name::Here;` to declare a class, or if you only want to +# export variables/subs, you can use `module`. module Hello::World { # Bracketed form # If `Hello` doesn't exist yet, it'll just be a "stub", @@ -1073,15 +1073,23 @@ ENTER { say "[*] Runs everytime you enter a block, repeats on loop blocks" } LEAVE { say "Runs everytime you leave a block, even when an exception happened. Repeats on loop blocks." } -PRE { say "Asserts a precondition at every block entry, - before ENTER (especially useful for loops)" } +PRE { + say "Asserts a precondition at every block entry, + before ENTER (especially useful for loops)"; + say "If this block doesn't return a truthy value, + an exception of type X::Phaser::PrePost is thrown."; +} # exemple: for 0..2 { PRE { $_ > 1 } # This is going to blow up with "Precondition failed" } -POST { say "Asserts a postcondition at every block exit, - after LEAVE (especially useful for loops)" } +POST { + say "Asserts a postcondition at every block exit, + after LEAVE (especially useful for loops)"; + say "If this block doesn't return a truthy value, + an exception of type X::Phaser::PrePost is thrown, like PRE."; +} for 0..2 { POST { $_ < 2 } # This is going to blow up with "Postcondition failed" } @@ -1522,14 +1530,17 @@ say $0; # The same as above. # IFF it can have more than one element # (so, with `*`, `+` and `**` (whatever the operands), but not with `?`). # Let's use examples to see that: -so 'fooABCbar' ~~ / foo ( A B C )? bar /; # `True` + +# Note: We quoted A B C to demonstrate that the whitespace between them isn't significant. +# If we want the whitespace to *be* significant there, we can use the :sigspace modifier. +so 'fooABCbar' ~~ / foo ( "A" "B" "C" )? bar /; # `True` say $/[0]; #=> ｢ABC｣ say $0.WHAT; #=> (Match) - # It can't be more than one, so it's only a single match object. -so 'foobar' ~~ / foo ( A B C )? bar /; #=> True + # There can't be more than one, so it's only a single match object. +so 'foobar' ~~ / foo ( "A" "B" "C" )? bar /; #=> True say $0.WHAT; #=> (Any) # This capture did not match, so it's empty -so 'foobar' ~~ / foo ( A B C ) ** 0..1 bar /; # `True` +so 'foobar' ~~ / foo ( "A" "B" "C" ) ** 0..1 bar /; # `True` say $0.WHAT; #=> (Array) # A specific quantifier will always capture an Array, # may it be a range or a specific value (even 1). -- cgit v1.2.3 From 66c4b1c01a26fed2b55ff50b4aba8b2c5eb9061c Mon Sep 17 00:00:00 2001 From: ven Date: Thu, 25 May 2017 15:06:13 +0200 Subject: fix #1155 --- perl6.html.markdown | 33 +++++++++++++++++++++++++++++---- 1 file changed, 29 insertions(+), 4 deletions(-) (limited to 'perl6.html.markdown') diff --git a/perl6.html.markdown b/perl6.html.markdown index ee94f5bf..d0ccdc9a 100644 --- a/perl6.html.markdown +++ b/perl6.html.markdown @@ -118,13 +118,38 @@ say %hash; # If it's a string, you can actually use <> # created with the `sub` keyword. sub say-hello { say "Hello, world" } -sub say-hello-to(Str $name) { # You can provide the type of an argument - # and it'll be checked at compile-time. - +# You can provide (typed) arguments. +# If specified, the type will be checked at compile-time if possible, +# otherwise at runtime. +sub say-hello-to(Str $name) { say "Hello, $name !"; } -## It can also have optional arguments: +# A sub returns the last value of the block. +sub return-value { + 5; +} +say return-value; # prints 5 +sub return-empty { +} +say return-empty; # prints Nil + +# Some control flow structures produce a value, like if: +sub return-if { + if True { + "Truthy"; + } +} +say return-if; # prints Truthy + +# Some don't, like for: +sub return-for { + for 1, 2, 3 { } +} +say return-for; # prints Nil + + +## A sub can have optional arguments: sub with-optional($arg?) { # the "?" marks the argument optional say "I might return `(Any)` (Perl's 'null'-like value) if I don't have an argument passed, or I'll return my argument"; -- cgit v1.2.3 From df6f8630a373806bac5016bd7bebd25c140557b6 Mon Sep 17 00:00:00 2001 From: Samantha McVey Date: Mon, 10 Jul 2017 21:40:05 -0700 Subject: [perl6] Lists are not Arrays. Make this clear Lists are immutable while Arrays are mutable. Arrays are which have the @ sigil. --- perl6.html.markdown | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) (limited to 'perl6.html.markdown') diff --git a/perl6.html.markdown b/perl6.html.markdown index d0ccdc9a..44960347 100644 --- a/perl6.html.markdown +++ b/perl6.html.markdown @@ -54,10 +54,11 @@ my $forced-bool = so $str; # And you can use the prefix `so` operator # which turns its operand into a Bool ``` -### Lists +### Arrays and Lists ```perl6 -# Lists represent multiple values. Their name start with `@`. +# Arrays represent multiple values. Their name start with `@`. +# Lists are similar but are an immutable type my @array = 'a', 'b', 'c'; # equivalent to : -- cgit v1.2.3 From 985d23a52b76593a120adff5381c2df3a80fe298 Mon Sep 17 00:00:00 2001 From: HairyFotr Date: Wed, 23 Aug 2017 10:14:39 +0200 Subject: Fix a bunch of typos --- perl6.html.markdown | 22 +++++++++++----------- 1 file changed, 11 insertions(+), 11 deletions(-) (limited to 'perl6.html.markdown') diff --git a/perl6.html.markdown b/perl6.html.markdown index 44960347..18326338 100644 --- a/perl6.html.markdown +++ b/perl6.html.markdown @@ -447,7 +447,7 @@ False ~~ True; # True # http://perlcabal.org/syn/S03.html#Smart_matching # You also, of course, have `<`, `<=`, `>`, `>=`. -# Their string equivalent are also avaiable : `lt`, `le`, `gt`, `ge`. +# Their string equivalent are also available : `lt`, `le`, `gt`, `ge`. 3 > 4; ## * Range constructors @@ -618,7 +618,7 @@ my @arrayplus3 = map(*+3, @array); # `*+3` is the same as `{ $_ + 3 }` my @arrayplus3 = map(*+*+3, @array); # Same as `-> $a, $b { $a + $b + 3 }` # also `sub ($a, $b) { $a + $b + 3 }` say (*/2)(4); #=> 2 - # Immediatly execute the function Whatever created. + # Immediately execute the function Whatever created. say ((*+3)/5)(5); #=> 1.6 # works even in parens ! @@ -750,7 +750,7 @@ sub call_say_dyn { my $*dyn_scoped_1 = 25; # Defines $*dyn_scoped_1 only for this sub. $*dyn_scoped_2 = 100; # Will change the value of the file scoped variable. say_dyn(); #=> 25 100 $*dyn_scoped 1 and 2 will be looked for in the call. - # It uses he value of $*dyn_scoped_1 from inside this sub's lexical + # It uses the value of $*dyn_scoped_1 from inside this sub's lexical # scope even though the blocks aren't nested (they're call-nested). } say_dyn(); #=> 1 10 @@ -816,7 +816,7 @@ $class-obj.other-attrib = 10; # This, however, works, because the public # Perl 6 also has inheritance (along with multiple inheritance) # While `method`'s are inherited, `submethod`'s are not. # Submethods are useful for object construction and destruction tasks, -# such as BUILD, or methods that must be overriden by subtypes. +# such as BUILD, or methods that must be overridden by subtypes. # We will learn about BUILD later on. class Parent { @@ -840,7 +840,7 @@ $Richard.talk; #=> "Hi, my name is Richard" # # $Richard is able to access the submethod, he knows how to say his name. my Child $Madison .= new(age => 1, name => 'Madison'); -$Madison.talk; # prints "Goo goo ga ga" due to the overrided method. +$Madison.talk; # prints "Goo goo ga ga" due to the overridden method. # $Madison.favorite-color does not work since it is not inherited # When you use `my T $var`, `$var` starts off with `T` itself in it, @@ -1054,7 +1054,7 @@ say why-not[^5]; #=> 5 15 25 35 45 ## * `state` (happens at run time, but only once) # State variables are only initialized one time -# (they exist in other langages such as C as `static`) +# (they exist in other languages such as C as `static`) sub fixed-rand { state $val = rand; say $val; @@ -1105,7 +1105,7 @@ PRE { say "If this block doesn't return a truthy value, an exception of type X::Phaser::PrePost is thrown."; } -# exemple: +# example: for 0..2 { PRE { $_ > 1 } # This is going to blow up with "Precondition failed" } @@ -1204,7 +1204,7 @@ say (1, 10, (20, 10) ).flat; #> (1 10 20 10) Now the iterable is flat # - `lazy` - Defer actual evaluation until value is fetched (forces lazy context) my @lazy-array = (1..100).lazy; -say @lazy-array.is-lazy; #> True # Check for lazyness with the `is-lazy` method. +say @lazy-array.is-lazy; #> True # Check for laziness with the `is-lazy` method. say @lazy-array; #> [...] List has not been iterated on! my @lazy-array { .print }; # This works and will only do as much work as is # needed. @@ -1599,7 +1599,7 @@ so 'ayc' ~~ / a [ b | y ] c /; # `True`. Obviously enough ... # To decide which part is the "longest", it first splits the regex in two parts: # The "declarative prefix" (the part that can be statically analyzed) # and the procedural parts. -# Declarative prefixes include alternations (`|`), conjuctions (`&`), +# Declarative prefixes include alternations (`|`), conjunctions (`&`), # sub-rule calls (not yet introduced), literals, characters classes and quantifiers. # The latter include everything else: back-references, code assertions, # and other things that can't traditionnaly be represented by normal regexps. @@ -1755,10 +1755,10 @@ If you want to go further, you can: This will give you a dropdown menu of all the pages referencing your search term (Much better than using Google to find Perl 6 documents!) - Read the [Perl 6 Advent Calendar](http://perl6advent.wordpress.com/). This - is a great source of Perl 6 snippets and explainations. If the docs don't + is a great source of Perl 6 snippets and explanations. If the docs don't describe something well enough, you may find more detailed information here. This information may be a bit older but there are many great examples and - explainations. Posts stopped at the end of 2015 when the language was declared + explanations. Posts stopped at the end of 2015 when the language was declared stable and Perl 6.c was released. - Come along on `#perl6` at `irc.freenode.net`. The folks here are always helpful. - Check the [source of Perl 6's functions and classes](https://github.com/rakudo/rakudo/tree/nom/src/core). Rakudo is mainly written in Perl 6 (with a lot of NQP, "Not Quite Perl", a Perl 6 subset easier to implement and optimize). -- cgit v1.2.3 From acdbaec28ec8cc6e90c28f2cb5d873338f0bfc4f Mon Sep 17 00:00:00 2001 From: Mario Date: Mon, 4 Sep 2017 16:07:47 +0200 Subject: removed the vimformation did not render resp. markdown was not upped with it --- perl6.html.markdown | 2 -- 1 file changed, 2 deletions(-) (limited to 'perl6.html.markdown') diff --git a/perl6.html.markdown b/perl6.html.markdown index 18326338..364711af 100644 --- a/perl6.html.markdown +++ b/perl6.html.markdown @@ -1763,5 +1763,3 @@ If you want to go further, you can: - Come along on `#perl6` at `irc.freenode.net`. The folks here are always helpful. - Check the [source of Perl 6's functions and classes](https://github.com/rakudo/rakudo/tree/nom/src/core). Rakudo is mainly written in Perl 6 (with a lot of NQP, "Not Quite Perl", a Perl 6 subset easier to implement and optimize). - Read [the language design documents](http://design.perl6.org). They explain P6 from an implementor point-of-view, but it's still very interesting. - - [//]: # ( vim: set filetype=perl softtabstop=2 shiftwidth=2 expandtab cc=80 : ) -- cgit v1.2.3 From c8ba31adb47777db7bc0669b20474f7bac921eff Mon Sep 17 00:00:00 2001 From: Keith Miyake Date: Thu, 28 Sep 2017 00:51:07 -0700 Subject: [perl6/en] Formatting consistency --- perl6.html.markdown | 1274 ++++++++++++++++++++++++++------------------------- 1 file changed, 654 insertions(+), 620 deletions(-) (limited to 'perl6.html.markdown') diff --git a/perl6.html.markdown b/perl6.html.markdown index 364711af..2821f0d4 100644 --- a/perl6.html.markdown +++ b/perl6.html.markdown @@ -13,8 +13,8 @@ least the next hundred years. The primary Perl 6 compiler is called [Rakudo](http://rakudo.org), which runs on the JVM and [the MoarVM](http://moarvm.com). -Meta-note : the triple pound signs are here to denote headlines, -double paragraphs, and single notes. +Meta-note : double pound signs (##) are used to indicate paragraphs, while +single pound signs (#) indicate notes. `#=>` represents the output of a command. @@ -30,9 +30,9 @@ double paragraphs, and single notes. ## Variables ```perl6 -# In Perl 6, you declare a lexical variable using `my` +## In Perl 6, you declare a lexical variable using `my` my $variable; -# Perl 6 has 4 kinds of variables: +## Perl 6 has 3 basic types of variables: scalars, arrays, and hashes. ``` ### Scalars @@ -44,9 +44,9 @@ my $str = 'String'; # double quotes allow for interpolation (which we'll see later): my $str2 = "String"; -# Variable names can contain but not end with simple quotes and dashes, -# and can contain (and end with) underscores : -# my $weird'variable-name_ = 5; # works ! +## Variable names can contain but not end with simple quotes and dashes, +## and can contain (and end with) underscores : +my $weird'variable-name_ = 5; # works ! my $bool = True; # `True` and `False` are Perl 6's boolean values. my $inverse = !$bool; # You can invert a bool with the prefix `!` operator @@ -57,13 +57,13 @@ my $forced-bool = so $str; # And you can use the prefix `so` operator ### Arrays and Lists ```perl6 -# Arrays represent multiple values. Their name start with `@`. -# Lists are similar but are an immutable type +## Arrays represent multiple values. Their name start with `@`. +## Lists are similar but are an immutable type. my @array = 'a', 'b', 'c'; # equivalent to : my @letters = ; # array of words, delimited by space. - # Similar to perl5's qw, or Ruby's %w. + # Similar to perl5's qw, or Ruby's %w. my @array = 1, 2, 3; say @array[2]; # Array indices start at 0 -- This is the third element @@ -82,24 +82,25 @@ say @array; #=> a 6 b ### Hashes, or key-value Pairs. ```perl6 -# Hashes are pairs of keys and values. -# You can construct a Pair object using the syntax `Key => Value`. -# Hash tables are very fast for lookup, and are stored unordered. -# Keep in mind that keys get "flattened" in hash context, and any duplicated -# keys are deduplicated. +## Hashes are pairs of keys and values. +## You can construct a Pair object using the syntax `Key => Value`. +## Hash tables are very fast for lookup, and are stored unordered. +## Keep in mind that keys get "flattened" in hash context, and any duplicated +## keys are deduplicated. my %hash = 1 => 2, 3 => 4; my %hash = foo => "bar", # keys get auto-quoted "some other" => "value", # trailing commas are okay ; -# Even though hashes are internally stored differently than arrays, -# Perl 6 allows you to easily create a hash from an even numbered array: + +## Even though hashes are internally stored differently than arrays, +## Perl 6 allows you to easily create a hash from an even numbered array: my %hash = ; my %hash = key1 => 'value1', key2 => 'value2'; # same result as above -# You can also use the "colon pair" syntax: -# (especially handy for named parameters that you'll see later) +## You can also use the "colon pair" syntax: +## (especially handy for named parameters that you'll see later) my %hash = :w(1), # equivalent to `w => 1` # this is useful for the `True` shortcut: :truey, # equivalent to `:truey(True)`, or `truey => True` @@ -115,18 +116,18 @@ say %hash; # If it's a string, you can actually use <> ## Subs ```perl6 -# subroutines or functions as most other languages call them are -# created with the `sub` keyword. +## Subroutines, or functions as most other languages call them, are +## created with the `sub` keyword. sub say-hello { say "Hello, world" } -# You can provide (typed) arguments. -# If specified, the type will be checked at compile-time if possible, -# otherwise at runtime. +## You can provide (typed) arguments. +## If specified, the type will be checked at compile-time if possible, +## otherwise at runtime. sub say-hello-to(Str $name) { say "Hello, $name !"; } -# A sub returns the last value of the block. +## A sub returns the last value of the block. sub return-value { 5; } @@ -135,7 +136,7 @@ sub return-empty { } say return-empty; # prints Nil -# Some control flow structures produce a value, like if: +## Some control flow structures produce a value, like if: sub return-if { if True { "Truthy"; @@ -143,13 +144,12 @@ sub return-if { } say return-if; # prints Truthy -# Some don't, like for: +## Some don't, like for: sub return-for { for 1, 2, 3 { } } say return-for; # prints Nil - ## A sub can have optional arguments: sub with-optional($arg?) { # the "?" marks the argument optional say "I might return `(Any)` (Perl's 'null'-like value) if I don't have @@ -170,20 +170,20 @@ hello-to('You'); #=> Hello, You ! ## You can also, by using a syntax akin to the one of hashes ## (yay unified syntax !), pass *named* arguments to a `sub`. -# They're optional, and will default to "Any". +## They're optional, and will default to "Any". sub with-named($normal-arg, :$named) { say $normal-arg + $named; } with-named(1, named => 6); #=> 7 -# There's one gotcha to be aware of, here: -# If you quote your key, Perl 6 won't be able to see it at compile time, -# and you'll have a single Pair object as a positional parameter, -# which means this fails: +## There's one gotcha to be aware of, here: +## If you quote your key, Perl 6 won't be able to see it at compile time, +## and you'll have a single Pair object as a positional parameter, +## which means this fails: with-named(1, 'named' => 6); with-named(2, :named(5)); #=> 7 -# To make a named argument mandatory, you can use `?`'s inverse, `!` +## To make a named argument mandatory, you can use `?`'s inverse, `!` sub with-mandatory-named(:$str!) { say "$str !"; } @@ -195,7 +195,7 @@ with-mandatory-named(3);# run time error:"Too many positional parameters passed" sub takes-a-bool($name, :$bool) { say "$name takes $bool"; } -# ... you can use the same "short boolean" hash syntax: +## ... you can use the same "short boolean" hash syntax: takes-a-bool('config', :bool); # config takes True takes-a-bool('config', :!bool); # config takes False @@ -206,15 +206,15 @@ sub named-def(:$def = 5) { named-def; #=> 5 named-def(def => 15); #=> 15 -# Since you can omit parenthesis to call a function with no arguments, -# you need "&" in the name to store `say-hello` in a variable. +## Since you can omit parenthesis to call a function with no arguments, +## you need "&" in the name to store `say-hello` in a variable. my &s = &say-hello; my &other-s = sub { say "Anonymous function !" } -# A sub can have a "slurpy" parameter, or "doesn't-matter-how-many" +## A sub can have a "slurpy" parameter, or "doesn't-matter-how-many" sub as-many($head, *@rest) { #`*@` (slurpy) will "take everything else" -# Note: you can have parameters *before* a slurpy one (like here), -# but not *after*. +## Note: you can have parameters *before* a slurpy one (like here), +## but not *after*. say @rest.join(' / ') ~ " !"; } say as-many('Happy', 'Happy', 'Birthday'); #=> Happy / Birthday ! @@ -222,8 +222,8 @@ say as-many('Happy', 'Happy', 'Birthday'); #=> Happy / Birthday ! # consume the parameter before. ## You can call a function with an array using the -# "argument list flattening" operator `|` -# (it's not actually the only role of this operator, but it's one of them) +## "argument list flattening" operator `|` +## (it's not actually the only role of this operator, but it's one of them) sub concat3($a, $b, $c) { say "$a, $b, $c"; } @@ -234,12 +234,12 @@ concat3(|@array); #=> a, b, c ## Containers ```perl6 -# In Perl 6, values are actually stored in "containers". -# The assignment operator asks the container on the left to store the value on -# its right. When passed around, containers are marked as immutable. -# Which means that, in a function, you'll get an error if you try to -# mutate one of your arguments. -# If you really need to, you can ask for a mutable container using `is rw`: +## In Perl 6, values are actually stored in "containers". +## The assignment operator asks the container on the left to store the value on +## its right. When passed around, containers are marked as immutable. +## Which means that, in a function, you'll get an error if you try to +## mutate one of your arguments. +## If you really need to, you can ask for a mutable container using `is rw`: sub mutate($n is rw) { $n++; say "\$n is now $n !"; @@ -248,15 +248,15 @@ sub mutate($n is rw) { my $m = 42; mutate $m; # $n is now 43 ! -# This works because we are passing the container $m to mutate. If we try -# to just pass a number instead of passing a variable it won't work because -# there is no container being passed and integers are immutable by themselves: +## This works because we are passing the container $m to mutate. If we try +## to just pass a number instead of passing a variable it won't work because +## there is no container being passed and integers are immutable by themselves: mutate 42; # Parameter '$n' expected a writable container, but got Int value -# If what you want a copy instead, use `is copy`. +## If what you want a copy instead, use `is copy`. -# A sub itself returns a container, which means it can be marked as rw: +## A sub itself returns a container, which means it can be marked as rw: my $x = 42; sub x-store() is rw { $x } x-store() = 52; # in this case, the parentheses are mandatory @@ -268,12 +268,12 @@ say $x; #=> 52 ### Conditionals ```perl6 -# - `if` -# Before talking about `if`, we need to know which values are "Truthy" -# (represent True), and which are "Falsey" (or "Falsy") -- represent False. -# Only these values are Falsey: 0, (), {}, "", Nil, A type (like `Str` or `Int`) -# and of course False itself. -# Every other value is Truthy. +## - `if` +## Before talking about `if`, we need to know which values are "Truthy" +## (represent True), and which are "Falsey" (or "Falsy") -- represent False. +## Only these values are Falsey: 0, (), {}, "", Nil, A type (like `Str` or +## `Int`) and of course False itself. +## Every other value is Truthy. if True { say "It's true !"; } @@ -282,17 +282,17 @@ unless False { say "It's not false !"; } -# As you can see, you don't need parentheses around conditions. -# However, you do need the brackets around the "body" block: +## As you can see, you don't need parentheses around conditions. +## However, you do need the brackets around the "body" block: # if (true) say; # This doesn't work ! -# You can also use their postfix versions, with the keyword after: +## You can also use their postfix versions, with the keyword after: say "Quite truthy" if True; -# - Ternary conditional, "?? !!" (like `x ? y : z` in some other languages) -# returns $value-if-true if the condition is true and $value-if-false -# if it is false. -# my $result = $value condition ?? $value-if-true !! $value-if-false; +## - Ternary conditional, "?? !!" (like `x ? y : z` in some other languages) +## returns $value-if-true if the condition is true and $value-if-false +## if it is false. +## my $result = $value condition ?? $value-if-true !! $value-if-false; my $age = 30; say $age > 18 ?? "You are an adult" !! "You are under 18"; @@ -301,18 +301,18 @@ say $age > 18 ?? "You are an adult" !! "You are under 18"; ### given/when, or switch ```perl6 -# - `given`-`when` looks like other languages' `switch`, but is much more -# powerful thanks to smart matching and Perl 6's "topic variable", $_. -# -# This variable contains the default argument of a block, -# a loop's current iteration (unless explicitly named), etc. -# -# `given` simply puts its argument into `$_` (like a block would do), -# and `when` compares it using the "smart matching" (`~~`) operator. -# -# Since other Perl 6 constructs use this variable (as said before, like `for`, -# blocks, etc), this means the powerful `when` is not only applicable along with -# a `given`, but instead anywhere a `$_` exists. +## - `given`-`when` looks like other languages' `switch`, but is much more +## powerful thanks to smart matching and Perl 6's "topic variable", $_. +## +## This variable contains the default argument of a block, +## a loop's current iteration (unless explicitly named), etc. +## +## `given` simply puts its argument into `$_` (like a block would do), +## and `when` compares it using the "smart matching" (`~~`) operator. +## +## Since other Perl 6 constructs use this variable (as said before, like `for`, +## blocks, etc), this means the powerful `when` is not only applicable along +## with a `given`, but instead anywhere a `$_` exists. given "foo bar" { say $_; #=> foo bar @@ -338,8 +338,8 @@ given "foo bar" { ### Looping constructs ```perl6 -# - `loop` is an infinite loop if you don't pass it arguments, -# but can also be a C-style `for` loop: +## - `loop` is an infinite loop if you don't pass it arguments, +## but can also be a C-style `for` loop: loop { say "This is an infinite loop !"; last; # last breaks out of the loop, like the `break` keyword in other @@ -353,13 +353,13 @@ loop (my $i = 0; $i < 5; $i++) { say "This is a C-style for loop !"; } -# - `for` - Passes through an array +## - `for` - Passes through an array for @array -> $variable { say "I've got $variable !"; } -# As we saw with given, for's default "current iteration" variable is `$_`. -# That means you can use `when` in a `for` just like you were in a `given`. +## As we saw with given, for's default "current iteration" variable is `$_`. +## That means you can use `when` in a `for` just like you were in a `given`. for @array { say "I've got $_"; @@ -370,13 +370,13 @@ for @array { for @array { # You can... - next if $_ == 3; # Skip to the next iteration (`continue` in C-like languages). - redo if $_ == 4; # Re-do the iteration, keeping the same topic variable (`$_`). - last if $_ == 5; # Or break out of a loop (like `break` in C-like languages). + next if $_ == 3; # Skip to the next iteration (`continue` in C-like languages) + redo if $_ == 4; # Re-do the iteration, keeping the same topic variable (`$_`) + last if $_ == 5; # Or break out of a loop (like `break` in C-like languages) } -# The "pointy block" syntax isn't specific to for. -# It's just a way to express a block in Perl6. +## The "pointy block" syntax isn't specific to for. +## It's just a way to express a block in Perl6. if long-computation() -> $result { say "The result is $result"; } @@ -387,99 +387,100 @@ if long-computation() -> $result { ```perl6 ## Since Perl languages are very much operator-based languages, ## Perl 6 operators are actually just funny-looking subroutines, in syntactic -## categories, like infix:<+> (addition) or prefix: (bool not). +## categories, like infix:<+> (addition) or prefix: (bool not). ## The categories are: -# - "prefix": before (like `!` in `!True`). -# - "postfix": after (like `++` in `$a++`). -# - "infix": in between (like `*` in `4 * 3`). -# - "circumfix": around (like `[`-`]` in `[1, 2]`). -# - "post-circumfix": around, after another term (like `{`-`}` in `%hash{'key'}`) +## - "prefix": before (like `!` in `!True`). +## - "postfix": after (like `++` in `$a++`). +## - "infix": in between (like `*` in `4 * 3`). +## - "circumfix": around (like `[`-`]` in `[1, 2]`). +## - "post-circumfix": around, after another term (like `{`-`}` in +## `%hash{'key'}`) ## The associativity and precedence list are explained below. -# Alright, you're set to go ! +## Alright, you're set to go ! ## * Equality Checking -# - `==` is numeric comparison +## - `==` is numeric comparison 3 == 4; # False 3 != 4; # True -# - `eq` is string comparison +## - `eq` is string comparison 'a' eq 'b'; 'a' ne 'b'; # not equal 'a' !eq 'b'; # same as above -# - `eqv` is canonical equivalence (or "deep equality") +## - `eqv` is canonical equivalence (or "deep equality") (1, 2) eqv (1, 3); -# - Smart Match Operator: `~~` -# Aliases the left hand side to $_ and then evaluates the right hand side. -# Here are some common comparison semantics: +## - Smart Match Operator: `~~` +## Aliases the left hand side to $_ and then evaluates the right hand side. +## Here are some common comparison semantics: -# String or Numeric Equality +## String or Numeric Equality 'Foo' ~~ 'Foo'; # True if strings are equal. 12.5 ~~ 12.50; # True if numbers are equal. -# Regex - For matching a regular expression against the left side. -# Returns a (Match) object, which evaluates as True if regexp matches. +## Regex - For matching a regular expression against the left side. +## Returns a (Match) object, which evaluates as True if regexp matches. my $obj = 'abc' ~~ /a/; say $obj; # ｢a｣ say $obj.WHAT; # (Match) -# Hashes +## Hashes 'key' ~~ %hash; # True if key exists in hash -# Type - Checks if left side "has type" (can check superclasses and roles) +## Type - Checks if left side "has type" (can check superclasses and roles) 1 ~~ Int; # True -# Smart-matching against a boolean always returns that boolean (and will warn). +## Smart-matching against a boolean always returns that boolean (and will warn). 1 ~~ True; # True False ~~ True; # True -# # General syntax is $arg ~~ &bool-returning-function; -# For a complete list of combinations, use this table: -# http://perlcabal.org/syn/S03.html#Smart_matching +## General syntax is $arg ~~ &bool-returning-function; +## For a complete list of combinations, use this table: +## http://perlcabal.org/syn/S03.html#Smart_matching -# You also, of course, have `<`, `<=`, `>`, `>=`. -# Their string equivalent are also available : `lt`, `le`, `gt`, `ge`. +## You also, of course, have `<`, `<=`, `>`, `>=`. +## Their string equivalent are also available : `lt`, `le`, `gt`, `ge`. 3 > 4; ## * Range constructors 3 .. 7; # 3 to 7, both included -# `^` on either side them exclusive on that side : +## `^` on either side them exclusive on that side : 3 ^..^ 7; # 3 to 7, not included (basically `4 .. 6`) -# This also works as a shortcut for `0..^N`: +## This also works as a shortcut for `0..^N`: ^10; # means 0..^10 -# This also allows us to demonstrate that Perl 6 has lazy/infinite arrays, -# using the Whatever Star: +## This also allows us to demonstrate that Perl 6 has lazy/infinite arrays, +## using the Whatever Star: my @array = 1..*; # 1 to Infinite ! `1..Inf` is the same. say @array[^10]; # you can pass arrays as subscripts and it'll return # an array of results. This will print # "1 2 3 4 5 6 7 8 9 10" (and not run out of memory !) -# Note : when reading an infinite list, Perl 6 will "reify" the elements -# it needs, then keep them in memory. They won't be calculated more than once. -# It also will never calculate more elements that are needed. -# Trying +## Note : when reading an infinite list, Perl 6 will "reify" the elements +## it needs, then keep them in memory. They won't be calculated more than once. +## It also will never calculate more elements that are needed. +## Trying -# An array subscript can also be a closure. -# It'll be called with the length as the argument +## An array subscript can also be a closure. +## It'll be called with the length as the argument say join(' ', @array[15..*]); #=> 15 16 17 18 19 -# which is equivalent to: +## which is equivalent to: say join(' ', @array[-> $n { 15..$n }]); -# Note: if you try to do either of those with an infinite array, -# you'll trigger an infinite loop (your program won't finish) +## Note: if you try to do either of those with an infinite array, +## you'll trigger an infinite loop (your program won't finish) -# You can use that in most places you'd expect, even assigning to an array +## You can use that in most places you'd expect, even assigning to an array my @numbers = ^20; -# Here numbers increase by "6"; more on `...` operator later. +## Here numbers increase by "6"; more on `...` operator later. my @seq = 3, 9 ... * > 95; # 3 9 15 21 27 [...] 81 87 93 99; @numbers[5..*] = 3, 9 ... *; # even though the sequence is infinite, # only the 15 needed values will be calculated. @@ -496,11 +497,11 @@ say @numbers; #=> 0 1 2 3 4 3 9 15 21 [...] 81 87 my ( $a, $b, $c ) = 1, 0, 2; $a && $b && $c; # Returns 0, the first False value -# || Returns the first argument that evaluates to True +## || Returns the first argument that evaluates to True $b || $a; # 1 -# And because you're going to want them, -# you also have compound assignment operators: +## And because you're going to want them, +## you also have compound assignment operators: $a *= 2; # multiply and assignment. Equivalent to $a = $a * 2; $b %%= 5; # divisible by and assignment @array .= sort; # calls the `sort` method and assigns the result back @@ -509,15 +510,15 @@ $b %%= 5; # divisible by and assignment ## More on subs ! ```perl6 -# As we said before, Perl 6 has *really* powerful subs. We're going to see -# a few more key concepts that make them better than in any other language :-). +## As we said before, Perl 6 has *really* powerful subs. We're going to see +## a few more key concepts that make them better than in any other language :-). ``` ### Unpacking ! ```perl6 -# It's the ability to "extract" arrays and keys (AKA "destructuring"). -# It'll work in `my`s and in parameter lists. +## It's the ability to "extract" arrays and keys (AKA "destructuring"). +## It'll work in `my`s and in parameter lists. my ($f, $g) = 1, 2; say $f; #=> 1 my ($, $, $h) = 1, 2, 3; # keep the non-interesting anonymous @@ -533,50 +534,50 @@ sub unpack_array(@array [$fst, $snd]) { unpack_array(@tail); #=> My first is 2, my second is 3 ! All in all, I'm 2 3 -# If you're not using the array itself, you can also keep it anonymous, -# much like a scalar: +## If you're not using the array itself, you can also keep it anonymous, +## much like a scalar: sub first-of-array(@ [$fst]) { $fst } first-of-array(@small); #=> 1 first-of-array(@tail); # Throws an error "Too many positional parameters passed" # (which means the array is too big). -# You can also use a slurp ... +## You can also use a slurp ... sub slurp-in-array(@ [$fst, *@rest]) { # You could keep `*@rest` anonymous say $fst + @rest.elems; # `.elems` returns a list's length. # Here, `@rest` is `(3,)`, since `$fst` holds the `2`. } slurp-in-array(@tail); #=> 3 -# You could even extract on a slurpy (but it's pretty useless ;-).) +## You could even extract on a slurpy (but it's pretty useless ;-).) sub fst(*@ [$fst]) { # or simply : `sub fst($fst) { ... }` say $fst; } fst(1); #=> 1 fst(1, 2); # errors with "Too many positional parameters passed" -# You can also destructure hashes (and classes, which you'll learn about later !) -# The syntax is basically `%hash-name (:key($variable-to-store-value-in))`. -# The hash can stay anonymous if you only need the values you extracted. +## You can also destructure hashes (and classes, which you'll learn about later) +## The syntax is basically `%hash-name (:key($variable-to-store-value-in))`. +## The hash can stay anonymous if you only need the values you extracted. sub key-of(% (:value($val), :qua($qua))) { say "Got val $val, $qua times."; } -# Then call it with a hash: (you need to keep the brackets for it to be a hash) +## Then call it with a hash: (you need to keep the brackets for it to be a hash) key-of({value => 'foo', qua => 1}); #key-of(%hash); # the same (for an equivalent `%hash`) ## The last expression of a sub is returned automatically -# (though you may use the `return` keyword, of course): +## (though you may use the `return` keyword, of course): sub next-index($n) { $n + 1; } my $new-n = next-index(3); # $new-n is now 4 -# This is true for everything, except for the looping constructs -# (due to performance reasons): there's reason to build a list -# if we're just going to discard all the results. -# If you still want to build one, you can use the `do` statement prefix: -# (or the `gather` prefix, which we'll see later) +## This is true for everything, except for the looping constructs +## (due to performance reasons): there's reason to build a list +## if we're just going to discard all the results. +## If you still want to build one, you can use the `do` statement prefix: +## (or the `gather` prefix, which we'll see later) sub list-of($n) { do for ^$n { # note the use of the range-to prefix operator `^` (`0..^N`) $_ # current loop iteration @@ -590,16 +591,16 @@ my @list3 = list-of(3); #=> (0, 1, 2) ```perl6 ## You can create a lambda with `-> {}` ("pointy block") or `{}` ("block") my &lambda = -> $argument { "The argument passed to this lambda is $argument" } -# `-> {}` and `{}` are pretty much the same thing, except that the former can -# take arguments, and that the latter can be mistaken as a hash by the parser. +## `-> {}` and `{}` are pretty much the same thing, except that the former can +## take arguments, and that the latter can be mistaken as a hash by the parser. -# We can, for example, add 3 to each value of an array using map: +## We can, for example, add 3 to each value of an array using map: my @arrayplus3 = map({ $_ + 3 }, @array); # $_ is the implicit argument -# A sub (`sub {}`) has different semantics than a block (`{}` or `-> {}`): -# A block doesn't have a "function context" (though it can have arguments), -# which means that if you return from it, -# you're going to return from the parent function. Compare: +## A sub (`sub {}`) has different semantics than a block (`{}` or `-> {}`): +## A block doesn't have a "function context" (though it can have arguments), +## which means that if you return from it, +## you're going to return from the parent function. Compare: sub is-in(@array, $elem) { # this will `return` out of the `is-in` sub # once the condition evaluated to True, the loop won't be run anymore @@ -612,8 +613,8 @@ sub truthy-array(@array) { # ^ the `return` only returns from the anonymous `sub` } -# You can also use the "whatever star" to create an anonymous function -# (it'll stop at the furthest operator in the current expression) +## You can also use the "whatever star" to create an anonymous function +## (it'll stop at the furthest operator in the current expression) my @arrayplus3 = map(*+3, @array); # `*+3` is the same as `{ $_ + 3 }` my @arrayplus3 = map(*+*+3, @array); # Same as `-> $a, $b { $a + $b + 3 }` # also `sub ($a, $b) { $a + $b + 3 }` @@ -622,41 +623,41 @@ say (*/2)(4); #=> 2 say ((*+3)/5)(5); #=> 1.6 # works even in parens ! -# But if you need to have more than one argument (`$_`) -# in a block (without wanting to resort to `-> {}`), -# you can also use the implicit argument syntax, `$^` : +## But if you need to have more than one argument (`$_`) +## in a block (without wanting to resort to `-> {}`), +## you can also use the implicit argument syntax, `$^` : map({ $^a + $^b + 3 }, @array); # equivalent to following: map(sub ($a, $b) { $a + $b + 3 }, @array); # (here with `sub`) -# Note : those are sorted lexicographically. +## Note : those are sorted lexicographically. # `{ $^b / $^a }` is like `-> $a, $b { $b / $a }` ``` ### About types... ```perl6 -# Perl6 is gradually typed. This means you can specify the type -# of your variables/arguments/return types, or you can omit them -# and they'll default to "Any". -# You obviously get access to a few base types, like Int and Str. -# The constructs for declaring types are "class", "role", -# which you'll see later. - -# For now, let us examine "subset": -# a "subset" is a "sub-type" with additional checks. -# For example: "a very big integer is an Int that's greater than 500" -# You can specify the type you're subtyping (by default, Any), -# and add additional checks with the "where" keyword: +## Perl6 is gradually typed. This means you can specify the type +## of your variables/arguments/return types, or you can omit them +## and they'll default to "Any". +## You obviously get access to a few base types, like Int and Str. +## The constructs for declaring types are "class", "role", +## which you'll see later. + +## For now, let us examine "subset": +## a "subset" is a "sub-type" with additional checks. +## For example: "a very big integer is an Int that's greater than 500" +## You can specify the type you're subtyping (by default, Any), +## and add additional checks with the "where" keyword: subset VeryBigInteger of Int where * > 500; ``` ### Multiple Dispatch ```perl6 -# Perl 6 can decide which variant of a `sub` to call based on the type of the -# arguments, or on arbitrary preconditions, like with a type or a `where`: +## Perl 6 can decide which variant of a `sub` to call based on the type of the +## arguments, or on arbitrary preconditions, like with a type or a `where`: -# with types +## with types multi sub sayit(Int $n) { # note the `multi` keyword here say "Number: $n"; } @@ -667,7 +668,7 @@ sayit("foo"); # prints "String: foo" sayit(True); # fails at *compile time* with # "calling 'sayit' will never work with arguments of types ..." -# with arbitrary precondition (remember subsets?): +## with arbitrary precondition (remember subsets?): multi is-big(Int $n where * > 50) { "Yes !" } # using a closure multi is-big(Int $ where 10..50) { "Quite." } # Using smart-matching # (could use a regexp, etc) @@ -679,7 +680,7 @@ multi odd-or-even(Even) { "Even" } # The main case using the type. # We don't name the argument. multi odd-or-even($) { "Odd" } # "else" -# You can even dispatch based on a positional's argument presence ! +## You can even dispatch based on a positional's argument presence ! multi with-or-without-you(:$with!) { # You need make it mandatory to # be able to dispatch against it. say "I can live ! Actually, I can't."; @@ -687,26 +688,26 @@ multi with-or-without-you(:$with!) { # You need make it mandatory to multi with-or-without-you { say "Definitely can't live."; } -# This is very, very useful for many purposes, like `MAIN` subs (covered later), -# and even the language itself is using it in several places. -# -# - `is`, for example, is actually a `multi sub` named `trait_mod:`, -# and it works off that. -# - `is rw`, is simply a dispatch to a function with this signature: -# sub trait_mod:(Routine $r, :$rw!) {} -# -# (commented because running this would be a terrible idea !) +## This is very, very useful for many purposes, like `MAIN` subs (covered +## later), and even the language itself is using it in several places. +## +## - `is`, for example, is actually a `multi sub` named `trait_mod:`, +## and it works off that. +## - `is rw`, is simply a dispatch to a function with this signature: +## sub trait_mod:(Routine $r, :$rw!) {} +## +## (commented because running this would be a terrible idea !) ``` ## Scoping ```perl6 -# In Perl 6, unlike many scripting languages, (such as Python, Ruby, PHP), -# you must declare your variables before using them. The `my` declarator -# you have learned uses "lexical scoping". There are a few other declarators, -# (`our`, `state`, ..., ) which we'll see later. -# This is called "lexical scoping", where in inner blocks, -# you can access variables from outer blocks. +## In Perl 6, unlike many scripting languages, (such as Python, Ruby, PHP), +## you must declare your variables before using them. The `my` declarator +## you have learned uses "lexical scoping". There are a few other declarators, +## (`our`, `state`, ..., ) which we'll see later. +## This is called "lexical scoping", where in inner blocks, +## you can access variables from outer blocks. my $file_scoped = 'Foo'; sub outer { my $outer_scoped = 'Bar'; @@ -717,27 +718,27 @@ sub outer { } outer()(); #=> 'Foo Bar' -# As you can see, `$file_scoped` and `$outer_scoped` were captured. -# But if we were to try and use `$bar` outside of `foo`, -# the variable would be undefined (and you'd get a compile time error). +## As you can see, `$file_scoped` and `$outer_scoped` were captured. +## But if we were to try and use `$bar` outside of `foo`, +## the variable would be undefined (and you'd get a compile time error). ``` ## Twigils ```perl6 -# There are many special `twigils` (composed sigil's) in Perl 6. -# Twigils define the variables' scope. -# The * and ? twigils work on standard variables: -# * Dynamic variable -# ? Compile-time variable -# The ! and the . twigils are used with Perl 6's objects: -# ! Attribute (class member) -# . Method (not really a variable) - -# `*` Twigil: Dynamic Scope -# These variables use the`*` twigil to mark dynamically-scoped variables. -# Dynamically-scoped variables are looked up through the caller, not through -# the outer scope +## There are many special `twigils` (composed sigil's) in Perl 6. +## Twigils define the variables' scope. +## The * and ? twigils work on standard variables: +## * Dynamic variable +## ? Compile-time variable +## The ! and the . twigils are used with Perl 6's objects: +## ! Attribute (class member) +## . Method (not really a variable) + +## `*` Twigil: Dynamic Scope +## These variables use the`*` twigil to mark dynamically-scoped variables. +## Dynamically-scoped variables are looked up through the caller, not through +## the outer scope my $*dyn_scoped_1 = 1; my $*dyn_scoped_2 = 10; @@ -750,8 +751,9 @@ sub call_say_dyn { my $*dyn_scoped_1 = 25; # Defines $*dyn_scoped_1 only for this sub. $*dyn_scoped_2 = 100; # Will change the value of the file scoped variable. say_dyn(); #=> 25 100 $*dyn_scoped 1 and 2 will be looked for in the call. - # It uses the value of $*dyn_scoped_1 from inside this sub's lexical - # scope even though the blocks aren't nested (they're call-nested). + # It uses the value of $*dyn_scoped_1 from inside this sub's + # lexical scope even though the blocks aren't nested (they're + # call-nested). } say_dyn(); #=> 1 10 call_say_dyn(); #=> 25 100 @@ -764,20 +766,20 @@ say_dyn(); #=> 1 100 We changed the value of $*dyn_scoped_2 in call_say_dyn ## Object Model ```perl6 -# To call a method on an object, add a dot followed by the method name: -# => $object.method -# Classes are declared with the `class` keyword. Attributes are declared -# with the `has` keyword, and methods declared with `method`. -# Every attribute that is private uses the ! twigil for example: `$!attr`. -# Immutable public attributes use the `.` twigil. -# (you can make them mutable with `is rw`) -# The easiest way to remember the `$.` twigil is comparing it to how methods -# are called. - -# Perl 6's object model ("SixModel") is very flexible, -# and allows you to dynamically add methods, change semantics, etc ... -# (these will not all be covered here, and you should refer to: -# https://docs.perl6.org/language/objects.html. +## To call a method on an object, add a dot followed by the method name: +## => $object.method +## Classes are declared with the `class` keyword. Attributes are declared +## with the `has` keyword, and methods declared with `method`. +## Every attribute that is private uses the ! twigil for example: `$!attr`. +## Immutable public attributes use the `.` twigil. +## (you can make them mutable with `is rw`) +## The easiest way to remember the `$.` twigil is comparing it to how methods +## are called. + +## Perl 6's object model ("SixModel") is very flexible, +## and allows you to dynamically add methods, change semantics, etc ... +## (these will not all be covered here, and you should refer to: +## https://docs.perl6.org/language/objects.html. class Attrib-Class { has $.attrib; # `$.attrib` is immutable. @@ -801,11 +803,11 @@ class Attrib-Class { } }; -# Create a new instance of Attrib-Class with $.attrib set to 5 : -# Note: you can't set private-attribute from here (more later on). +## Create a new instance of Attrib-Class with $.attrib set to 5 : +## Note: you can't set private-attribute from here (more later on). my $class-obj = Attrib-Class.new(attrib => 5); say $class-obj.get-value; #=> 15 -#$class-obj.attrib = 5; # This fails, because the `has $.attrib` is immutable +# $class-obj.attrib = 5; # This fails, because the `has $.attrib` is immutable $class-obj.other-attrib = 10; # This, however, works, because the public # attribute is mutable (`rw`). ``` @@ -813,11 +815,11 @@ $class-obj.other-attrib = 10; # This, however, works, because the public ### Object Inheritance ```perl6 -# Perl 6 also has inheritance (along with multiple inheritance) -# While `method`'s are inherited, `submethod`'s are not. -# Submethods are useful for object construction and destruction tasks, -# such as BUILD, or methods that must be overridden by subtypes. -# We will learn about BUILD later on. +## Perl 6 also has inheritance (along with multiple inheritance) +## While `method`'s are inherited, `submethod`'s are not. +## Submethods are useful for object construction and destruction tasks, +## such as BUILD, or methods that must be overridden by subtypes. +## We will learn about BUILD later on. class Parent { has $.age; @@ -837,24 +839,24 @@ class Child is Parent { my Parent $Richard .= new(age => 40, name => 'Richard'); $Richard.favorite-color; #=> "My favorite color is Blue" $Richard.talk; #=> "Hi, my name is Richard" -# # $Richard is able to access the submethod, he knows how to say his name. +## $Richard is able to access the submethod, he knows how to say his name. my Child $Madison .= new(age => 1, name => 'Madison'); $Madison.talk; # prints "Goo goo ga ga" due to the overridden method. -# $Madison.favorite-color does not work since it is not inherited - -# When you use `my T $var`, `$var` starts off with `T` itself in it, -# so you can call `new` on it. -# (`.=` is just the dot-call and the assignment operator: -# `$a .= b` is the same as `$a = $a.b`) -# Also note that `BUILD` (the method called inside `new`) -# will set parent properties too, so you can pass `val => 5`. +# $Madison.favorite-color # does not work since it is not inherited + +## When you use `my T $var`, `$var` starts off with `T` itself in it, +## so you can call `new` on it. +## (`.=` is just the dot-call and the assignment operator: +## `$a .= b` is the same as `$a = $a.b`) +## Also note that `BUILD` (the method called inside `new`) +## will set parent properties too, so you can pass `val => 5`. ``` ### Roles, or Mixins ```perl6 -# Roles are supported too (also called Mixins in other languages) +## Roles are supported too (also called Mixins in other languages) role PrintableVal { has $!counter = 0; method print { @@ -862,105 +864,108 @@ role PrintableVal { } } -# you "import" a mixin (a "role") with "does": +## you "import" a mixin (a "role") with "does": class Item does PrintableVal { has $.val; - # When `does`-ed, a `role` literally "mixes in" the class: - # the methods and attributes are put together, which means a class can access - # the private attributes/methods of its roles (but not the inverse !): + ## When `does`-ed, a `role` literally "mixes in" the class: + ## the methods and attributes are put together, which means a class can access + ## the private attributes/methods of its roles (but not the inverse !): method access { say $!counter++; } - # However, this: - # method print {} - # is ONLY valid when `print` isn't a `multi` with the same dispatch. - # (this means a parent class can shadow a child class's `multi print() {}`, - # but it's an error if a role does) + ## However, this: + ## method print {} + ## is ONLY valid when `print` isn't a `multi` with the same dispatch. + ## (this means a parent class can shadow a child class's `multi print() {}`, + ## but it's an error if a role does) - # NOTE: You can use a role as a class (with `is ROLE`). In this case, methods - # will be shadowed, since the compiler will consider `ROLE` to be a class. + ## NOTE: You can use a role as a class (with `is ROLE`). In this case, + ## methods will be shadowed, since the compiler will consider `ROLE` to + ## be a class. } ``` ## Exceptions ```perl6 -# Exceptions are built on top of classes, in the package `X` (like `X::IO`). -# In Perl6 exceptions are automatically 'thrown' +## Exceptions are built on top of classes, in the package `X` (like `X::IO`). +## In Perl6 exceptions are automatically 'thrown' open 'foo'; #> Failed to open file foo: no such file or directory -# It will also print out what line the error was thrown at and other error info +## It will also print out what line the error was thrown at and other error info -# You can throw an exception using `die`: +## You can throw an exception using `die`: die 'Error!'; #=> Error! -# Or more explicitly: + +## Or more explicitly: die X::AdHoc.new(payload => 'Error!'); -# In Perl 6, `orelse` is similar to the `or` operator, except it only matches -# undefined variables instead of anything evaluating as false. -# Undefined values include: `Nil`, `Mu` and `Failure` as well as `Int`, `Str` -# and other types that have not been initialized to any value yet. -# You can check if something is defined or not using the defined method: +## In Perl 6, `orelse` is similar to the `or` operator, except it only matches +## undefined variables instead of anything evaluating as false. +## Undefined values include: `Nil`, `Mu` and `Failure` as well as `Int`, `Str` +## and other types that have not been initialized to any value yet. +## You can check if something is defined or not using the defined method: my $uninitialized; say $uninitiazilzed.defined; #> False -# When using `orelse` it will disarm the exception and alias $_ to that failure -# This will avoid it being automatically handled and printing lots of scary -# error messages to the screen. -# We can use the exception method on $_ to access the exception +## When using `orelse` it will disarm the exception and alias $_ to that failure +## This will avoid it being automatically handled and printing lots of scary +## error messages to the screen. +## We can use the exception method on $_ to access the exception open 'foo' orelse say "Something happened {.exception}"; -# This also works: + +## This also works: open 'foo' orelse say "Something happened $_"; #> Something happened #> Failed to open file foo: no such file or directory -# Both of those above work but in case we get an object from the left side that -# is not a failure we will probably get a warning. We see below how we can use -# `try` and `CATCH` to be more specific with the exceptions we catch. +## Both of those above work but in case we get an object from the left side that +## is not a failure we will probably get a warning. We see below how we can use +## `try` and `CATCH` to be more specific with the exceptions we catch. ``` ### Using `try` and `CATCH` ```perl6 -# By using `try` and `CATCH` you can contain and handle exceptions without -# disrupting the rest of the program. `try` will set the last exception to -# the special variable `$!` Note: This has no relation to $!variables. +## By using `try` and `CATCH` you can contain and handle exceptions without +## disrupting the rest of the program. `try` will set the last exception to +## the special variable `$!` Note: This has no relation to $!variables. try open 'foo'; say "Well, I tried! $!" if defined $!; #> Well, I tried! Failed to open file #foo: no such file or directory -# Now, what if we want more control over handling the exception? -# Unlike many other languages, in Perl 6, you put the `CATCH` block *within* -# the block to `try`. Similar to how $_ was set when we 'disarmed' the -# exception with orelse, we also use $_ in the CATCH block. -# Note: ($! is only set *after* the `try` block) -# By default, a `try` has a `CATCH` block that catches -# any exception (`CATCH { default {} }`). +## Now, what if we want more control over handling the exception? +## Unlike many other languages, in Perl 6, you put the `CATCH` block *within* +## the block to `try`. Similar to how $_ was set when we 'disarmed' the +## exception with orelse, we also use $_ in the CATCH block. +## Note: ($! is only set *after* the `try` block) +## By default, a `try` has a `CATCH` block that catches +## any exception (`CATCH { default {} }`). try { my $a = (0 %% 0); CATCH { say "Something happened: $_" } } #=> Something happened: Attempt to divide by zero using infix:<%%> -# You can redefine it using `when`s (and `default`) -# to handle the exceptions you want: +## You can redefine it using `when`s (and `default`) +## to handle the exceptions you want: try { open 'foo'; CATCH { # In the `CATCH` block, the exception is set to $_ when X::AdHoc { say "Error: $_" } #=>Error: Failed to open file /dir/foo: no such file or directory - # Any other exception will be re-raised, since we don't have a `default` - # Basically, if a `when` matches (or there's a `default`) marks the - # exception as - # "handled" so that it doesn't get re-thrown from the `CATCH`. - # You still can re-throw the exception (see below) by hand. + ## Any other exception will be re-raised, since we don't have a `default` + ## Basically, if a `when` matches (or there's a `default`) marks the + ## exception as + ## "handled" so that it doesn't get re-thrown from the `CATCH`. + ## You still can re-throw the exception (see below) by hand. } } -# There are also some subtleties to exceptions. Some Perl 6 subs return a -# `Failure`, which is a kind of "unthrown exception". They're not thrown until -# you tried to look at their content, unless you call `.Bool`/`.defined` on -# them - then they're handled. -# (the `.handled` method is `rw`, so you can mark it as `False` back yourself) -# -# You can throw a `Failure` using `fail`. Note that if the pragma `use fatal` -# is on, `fail` will throw an exception (like `die`). +## There are also some subtleties to exceptions. Some Perl 6 subs return a +## `Failure`, which is a kind of "unthrown exception". They're not thrown until +## you tried to look at their content, unless you call `.Bool`/`.defined` on +## them - then they're handled. +## (the `.handled` method is `rw`, so you can mark it as `False` back yourself) +## +## You can throw a `Failure` using `fail`. Note that if the pragma `use fatal` +## is on, `fail` will throw an exception (like `die`). fail "foo"; # We're not trying to access the value, so no problem. try { fail "foo"; @@ -969,28 +974,28 @@ try { } } -# There is also another kind of exception: Control exceptions. -# Those are "good" exceptions, which happen when you change your program's flow, -# using operators like `return`, `next` or `last`. -# You can "catch" those with `CONTROL` (not 100% working in Rakudo yet). +## There is also another kind of exception: Control exceptions. +## Those are "good" exceptions, which happen when you change your program's +## flow, using operators like `return`, `next` or `last`. +## You can "catch" those with `CONTROL` (not 100% working in Rakudo yet). ``` ## Packages ```perl6 -# Packages are a way to reuse code. Packages are like "namespaces", and any -# element of the six model (`module`, `role`, `class`, `grammar`, `subset` -# and `enum`) are actually packages. (Packages are the lowest common denominator) -# Packages are important - especially as Perl is well-known for CPAN, -# the Comprehensive Perl Archive Network. +## Packages are a way to reuse code. Packages are like "namespaces", and any +## element of the six model (`module`, `role`, `class`, `grammar`, `subset` and +## `enum`) are actually packages. (Packages are the lowest common denominator) +## Packages are important - especially as Perl is well-known for CPAN, +## the Comprehensive Perl Archive Network. -# You can use a module (bring its declarations into scope) with `use` +## You can use a module (bring its declarations into scope) with `use` use JSON::Tiny; # if you installed Rakudo* or Panda, you'll have this module say from-json('[1]').perl; #=> [1] -# You should not declare packages using the `package` keyword (unlike Perl 5). -# Instead, use `class Package::Name::Here;` to declare a class, or if you only want to -# export variables/subs, you can use `module`. +## You should not declare packages using the `package` keyword (unlike Perl 5). +## Instead, use `class Package::Name::Here;` to declare a class, or if you only +## want to export variables/subs, you can use `module`. module Hello::World { # Bracketed form # If `Hello` doesn't exist yet, it'll just be a "stub", @@ -1002,22 +1007,22 @@ unit module Parse::Text; # file-scoped form grammar Parse::Text::Grammar { # A grammar is a package, which you could `use` } # You will learn more about grammars in the regex section -# As said before, any part of the six model is also a package. -# Since `JSON::Tiny` uses (its own) `JSON::Tiny::Actions` class, you can use it: +## As said before, any part of the six model is also a package. +## Since `JSON::Tiny` uses its own `JSON::Tiny::Actions` class, you can use it: my $actions = JSON::Tiny::Actions.new; -# We'll see how to export variables and subs in the next part: +## We'll see how to export variables and subs in the next part: ``` ## Declarators ```perl6 -# In Perl 6, you get different behaviors based on how you declare a variable. -# You've already seen `my` and `has`, we'll now explore the others. +## In Perl 6, you get different behaviors based on how you declare a variable. +## You've already seen `my` and `has`, we'll now explore the others. ## * `our` declarations happen at `INIT` time -- (see "Phasers" below) -# It's like `my`, but it also creates a package variable. -# (All packagish things (`class`, `role`, etc) are `our` by default) +## It's like `my`, but it also creates a package variable. +## (All packagish things (`class`, `role`, etc) are `our` by default) module Var::Increment { our $our-var = 1; # Note: you can't put a type constraint like Int on an my $my-var = 22; # `our` variable. @@ -1044,26 +1049,26 @@ Var::Increment::Inc; #=> 3 # Notice how the value of $our-var was Var::Increment::unavailable; #> Could not find symbol '&unavailable' ## * `constant` (happens at `BEGIN` time) -# You can use the `constant` keyword to declare a compile-time variable/symbol: +## You can use the `constant` keyword to declare a compile-time variable/symbol: constant Pi = 3.14; constant $var = 1; -# And if you're wondering, yes, it can also contain infinite lists. +## And if you're wondering, yes, it can also contain infinite lists. constant why-not = 5, 15 ... *; say why-not[^5]; #=> 5 15 25 35 45 ## * `state` (happens at run time, but only once) -# State variables are only initialized one time -# (they exist in other languages such as C as `static`) +## State variables are only initialized one time +## (they exist in other languages such as C as `static`) sub fixed-rand { state $val = rand; say $val; } fixed-rand for ^10; # will print the same number 10 times -# Note, however, that they exist separately in different enclosing contexts. -# If you declare a function with a `state` within a loop, it'll re-create the -# variable for each iteration of the loop. See: +## Note, however, that they exist separately in different enclosing contexts. +## If you declare a function with a `state` within a loop, it'll re-create the +## variable for each iteration of the loop. See: for ^5 -> $a { sub foo { state $val = rand; # This will be a different value for every value of `$a` @@ -1078,13 +1083,14 @@ for ^5 -> $a { ## Phasers ```perl6 -# Phasers in Perl 6 are blocks that happen at determined points of time in your -# program. They are called phasers because they mark a change in the phase -# of a program. For example, when the program is compiled, a for loop runs, -# you leave a block, or an exception gets thrown. (`CATCH` is actually a phaser !) -# Some of them can be used for their return values, some of them can't -# (those that can have a "[*]" in the beginning of their explanation text). -# Let's have a look ! +## Phasers in Perl 6 are blocks that happen at determined points of time in your +## program. They are called phasers because they mark a change in the phase +## of a program. For example, when the program is compiled, a for loop runs, +## you leave a block, or an exception gets thrown. +## (`CATCH` is actually a phaser!) +## Some of them can be used for their return values, some of them can't +## (those that can have a "[*]" in the beginning of their explanation text). +## Let's have a look ! ## * Compile-time phasers BEGIN { say "[*] Runs at compile time, as soon as possible, only once" } @@ -1105,7 +1111,8 @@ PRE { say "If this block doesn't return a truthy value, an exception of type X::Phaser::PrePost is thrown."; } -# example: + +## example: for 0..2 { PRE { $_ > 1 } # This is going to blow up with "Precondition failed" } @@ -1122,8 +1129,10 @@ for 0..2 { ## * Block/exceptions phasers sub { - KEEP { say "Runs when you exit a block successfully (without throwing an exception)" } - UNDO { say "Runs when you exit a block unsuccessfully (by throwing an exception)" } + KEEP { say "Runs when you exit a block successfully + (without throwing an exception)" } + UNDO { say "Runs when you exit a block unsuccessfully + (by throwing an exception)" } } ## * Loop phasers @@ -1136,10 +1145,10 @@ for ^5 { ## * Role/class phasers COMPOSE { "When a role is composed into a class. /!\ NOT YET IMPLEMENTED" } -# They allow for cute tricks or clever code ...: +## They allow for cute tricks or clever code ...: say "This code took " ~ (time - CHECK time) ~ "s to compile"; -# ... or clever organization: +## ... or clever organization: sub do-db-stuff { $db.start-transaction; # start a new transaction KEEP $db.commit; # commit the transaction if all went well @@ -1150,29 +1159,29 @@ sub do-db-stuff { ## Statement prefixes ```perl6 -# Those act a bit like phasers: they affect the behavior of the following code. -# Though, they run in-line with the executable code, so they're in lowercase. -# (`try` and `start` are theoretically in that list, but explained somewhere else) -# Note: all of these (except start) don't need explicit brackets `{` and `}`. - -# - `do` (that you already saw) - runs a block or a statement as a term -# You can't normally use a statement as a value (or "term"): -# -# my $value = if True { 1 } # `if` is a statement - parse error -# -# This works: +## Those act a bit like phasers: they affect the behavior of the following code. +## Though, they run in-line with the executable code, so they're in lowercase. +## (`try` and `start` are theoretically in that list, but explained elsewhere) +## Note: all of these (except start) don't need explicit brackets `{` and `}`. + +## - `do` (that you already saw) - runs a block or a statement as a term +## You can't normally use a statement as a value (or "term"): +## +## my $value = if True { 1 } # `if` is a statement - parse error +## +## This works: my $a = do if True { 5 } # with `do`, `if` is now a term. -# - `once` - Makes sure a piece of code only runs once +## - `once` - Makes sure a piece of code only runs once for ^5 { once say 1 }; #=> 1 # Only prints ... once. -# Like `state`, they're cloned per-scope +## Like `state`, they're cloned per-scope for ^5 { sub { once say 1 }() } #=> 1 1 1 1 1 # Prints once per lexical scope -# - `gather` - Co-routine thread -# Gather allows you to `take` several values in an array, -# much like `do`, but allows you to take any expression. +## - `gather` - Co-routine thread +## Gather allows you to `take` several values in an array, +## much like `do`, but allows you to take any expression. say gather for ^5 { take $_ * 3 - 1; take $_ * 3 + 1; @@ -1183,41 +1192,43 @@ say join ',', gather if False { take 3; } # Doesn't print anything. -# - `eager` - Evaluate statement eagerly (forces eager context) -# Don't try this at home: -# -# eager 1..*; # this will probably hang for a while (and might crash ...). -# -# But consider: +## - `eager` - Evaluate statement eagerly (forces eager context) +## Don't try this at home: +## +## eager 1..*; # this will probably hang for a while (and might crash ...). +## +## But consider: constant thrice = gather for ^3 { say take $_ }; # Doesn't print anything -# versus: + +## versus: constant thrice = eager gather for ^3 { say take $_ }; #=> 0 1 2 ``` ## Iterables ```perl6 -# Iterables are objects that can be iterated similar to the `for` construct -# `flat`, flattens iterables: +## Iterables are objects that can be iterated similar to the `for` construct +## `flat`, flattens iterables: say (1, 10, (20, 10) ); #> (1 10 (20 10)) Notice how grouping is maintained say (1, 10, (20, 10) ).flat; #> (1 10 20 10) Now the iterable is flat -# - `lazy` - Defer actual evaluation until value is fetched (forces lazy context) +## - `lazy` - Defer actual evaluation until value is fetched +## (forces lazy context) my @lazy-array = (1..100).lazy; say @lazy-array.is-lazy; #> True # Check for laziness with the `is-lazy` method. say @lazy-array; #> [...] List has not been iterated on! -my @lazy-array { .print }; # This works and will only do as much work as is -# needed. +my @lazy-array { .print }; # This works and will only do as much work as + # is needed. [//]: # ( TODO explain that gather/take and map are all lazy) -# - `sink` - An `eager` that discards the results (forces sink context) +## - `sink` - An `eager` that discards the results (forces sink context) constant nilthingie = sink for ^3 { .say } #=> 0 1 2 say nilthingie.perl; #=> Nil -# - `quietly` blocks will suppress warnings: +## - `quietly` blocks will suppress warnings: quietly { warn 'This is a warning!' }; #=> No output -# - `contend` - Attempts side effects under STM -# Not yet implemented ! +## - `contend` - Attempts side effects under STM +## Not yet implemented ! ``` ## More operators thingies ! @@ -1225,18 +1236,18 @@ quietly { warn 'This is a warning!' }; #=> No output ```perl6 ## Everybody loves operators ! Let's get more of them -# The precedence list can be found here: -# https://docs.perl6.org/language/operators#Operator_Precedence -# But first, we need a little explanation about associativity: +## The precedence list can be found here: +## https://docs.perl6.org/language/operators#Operator_Precedence +## But first, we need a little explanation about associativity: -# * Binary operators: +## * Binary operators: $a ! $b ! $c; # with a left-associative `!`, this is `($a ! $b) ! $c` $a ! $b ! $c; # with a right-associative `!`, this is `$a ! ($b ! $c)` $a ! $b ! $c; # with a non-associative `!`, this is illegal $a ! $b ! $c; # with a chain-associative `!`, this is `($a ! $b) and ($b ! $c)` $a ! $b ! $c; # with a list-associative `!`, this is `infix:<>` -# * Unary operators: +## * Unary operators: !$a! # with left-associative `!`, this is `(!$a)!` !$a! # with right-associative `!`, this is `!($a!)` !$a! # with non-associative `!`, this is illegal @@ -1245,12 +1256,12 @@ $a ! $b ! $c; # with a list-associative `!`, this is `infix:<>` ### Create your own operators ! ```perl6 -# Okay, you've been reading all of that, so I guess I should try -# to show you something exciting. -# I'll tell you a little secret (or not-so-secret): -# In Perl 6, all operators are actually just funny-looking subroutines. +## Okay, you've been reading all of that, so I guess I should try +## to show you something exciting. +## I'll tell you a little secret (or not-so-secret): +## In Perl 6, all operators are actually just funny-looking subroutines. -# You can declare an operator just like you declare a sub: +## You can declare an operator just like you declare a sub: sub prefix:($winner) { # refer to the operator categories # (yes, it's the "words operator" `<>`) say "$winner Won !"; @@ -1258,7 +1269,7 @@ sub prefix:($winner) { # refer to the operator categories win "The King"; #=> The King Won ! # (prefix is before) -# you can still call the sub with its "full name" +## you can still call the sub with its "full name": say prefix:(True); #=> False sub postfix:(Int $n) { @@ -1281,7 +1292,7 @@ sub infix:(Int $n, Block $r) { # infix in the middle # You're very recommended to put spaces # around your infix operator calls. -# For circumfix and post-circumfix ones +## For circumfix and post-circumfix ones sub circumfix:<[ ]>(Int $n) { $n ** $n } @@ -1289,95 +1300,96 @@ say [5]; #=> 3125 # circumfix is around. Again, no whitespace. sub postcircumfix:<{ }>(Str $s, Int $idx) { - # post-circumfix is - # "after a term, around something" + ## post-circumfix is + ## "after a term, around something" $s.substr($idx, 1); } say "abc"{1}; #=> b # after the term `"abc"`, and around the index (1) -# This really means a lot -- because everything in Perl 6 uses this. -# For example, to delete a key from a hash, you use the `:delete` adverb -# (a simple named argument underneath): +## This really means a lot -- because everything in Perl 6 uses this. +## For example, to delete a key from a hash, you use the `:delete` adverb +## (a simple named argument underneath): %h{$key}:delete; -# equivalent to: +## equivalent to: postcircumfix:<{ }>(%h, $key, :delete); # (you can call operators like that) -# It's *all* using the same building blocks! -# Syntactic categories (prefix infix ...), named arguments (adverbs), ..., -# - used to build the language - are available to you. -# (you are, obviously, recommended against making an operator out of -# *everything* -- with great power comes great responsibility) +## It's *all* using the same building blocks! +## Syntactic categories (prefix infix ...), named arguments (adverbs), ..., +## - used to build the language - are available to you. +## (you are, obviously, recommended against making an operator out of +## *everything* -- with great power comes great responsibility) ``` ### Meta operators ! ```perl6 -# Oh boy, get ready. Get ready, because we're delving deep -# into the rabbit's hole, and you probably won't want to go -# back to other languages after reading that. -# (I'm guessing you don't want to already at that point). -# Meta-operators, as their name suggests, are *composed* operators. -# Basically, they're operators that apply another operator. +## Oh boy, get ready. Get ready, because we're delving deep +## into the rabbit's hole, and you probably won't want to go +## back to other languages after reading that. +## (I'm guessing you don't want to already at that point). +## Meta-operators, as their name suggests, are *composed* operators. +## Basically, they're operators that apply another operator. ## * Reduce meta-operator -# It's a prefix meta-operator that takes a binary function and -# one or many lists. If it doesn't get passed any argument, -# it either returns a "default value" for this operator -# (a meaningless value) or `Any` if there's none (examples below). -# -# Otherwise, it pops an element from the list(s) one at a time, and applies -# the binary function to the last result (or the list's first element) -# and the popped element. -# -# To sum a list, you could use the reduce meta-operator with `+`, i.e.: +## It's a prefix meta-operator that takes a binary function and +## one or many lists. If it doesn't get passed any argument, +## it either returns a "default value" for this operator +## (a meaningless value) or `Any` if there's none (examples below). +## +## Otherwise, it pops an element from the list(s) one at a time, and applies +## the binary function to the last result (or the list's first element) +## and the popped element. +## +## To sum a list, you could use the reduce meta-operator with `+`, i.e.: say [+] 1, 2, 3; #=> 6 -# equivalent to `(1+2)+3` +## equivalent to `(1+2)+3` + say [*] 1..5; #=> 120 -# equivalent to `((((1*2)*3)*4)*5)`. +## equivalent to `((((1*2)*3)*4)*5)`. -# You can reduce with any operator, not just with mathematical ones. -# For example, you could reduce with `//` to get -# the first defined element of a list: +## You can reduce with any operator, not just with mathematical ones. +## For example, you could reduce with `//` to get +## the first defined element of a list: say [//] Nil, Any, False, 1, 5; #=> False # (Falsey, but still defined) - -# Default value examples: +## Default value examples: say [*] (); #=> 1 say [+] (); #=> 0 # meaningless values, since N*1=N and N+0=N. say [//]; #=> (Any) # There's no "default value" for `//`. -# You can also call it with a function you made up, using double brackets: +## You can also call it with a function you made up, using double brackets: sub add($a, $b) { $a + $b } say [[&add]] 1, 2, 3; #=> 6 ## * Zip meta-operator -# This one is an infix meta-operator than also can be used as a "normal" -# operator. It takes an optional binary function (by default, it just creates -# a pair), and will pop one value off of each array and call its binary function -# on these until it runs out of elements. It returns an array with all of these -# new elements. -(1, 2) Z (3, 4); # ((1, 3), (2, 4)), since by default, the function makes an array +## This one is an infix meta-operator than also can be used as a "normal" +## operator. It takes an optional binary function (by default, it just creates +## a pair), and will pop one value off of each array and call its binary +## function on these until it runs out of elements. It returns an array with +## all of these new elements. +(1, 2) Z (3, 4); # ((1, 3), (2, 4)), since by default, the function + # makes an array. 1..3 Z+ 4..6; # (5, 7, 9), using the custom infix:<+> function -# Since `Z` is list-associative (see the list above), -# you can use it on more than one list +## Since `Z` is list-associative (see the list above), +## you can use it on more than one list (True, False) Z|| (False, False) Z|| (False, False); # (True, False) -# And, as it turns out, you can also use the reduce meta-operator with it: +## And, as it turns out, you can also use the reduce meta-operator with it: [Z||] (True, False), (False, False), (False, False); # (True, False) ## And to end the operator list: ## * Sequence operator -# The sequence operator is one of Perl 6's most powerful features: -# it's composed of first, on the left, the list you want Perl 6 to deduce from -# (and might include a closure), and on the right, a value or the predicate -# that says when to stop (or Whatever for a lazy infinite list). +## The sequence operator is one of Perl 6's most powerful features: +## it's composed of first, on the left, the list you want Perl 6 to deduce from +## (and might include a closure), and on the right, a value or the predicate +## that says when to stop (or Whatever for a lazy infinite list). my @list = 1, 2, 3 ... 10; # basic deducing #my @list = 1, 3, 6 ... 10; # this dies because Perl 6 can't figure out the end my @list = 1, 2, 3 ...^ 10; # as with ranges, you can exclude the last element @@ -1390,175 +1402,189 @@ my @fib = 1, 1, *+* ... *; # lazy infinite list of fibonacci series, # computed using a closure! my @fib = 1, 1, -> $a, $b { $a + $b } ... *; # (equivalent to the above) my @fib = 1, 1, { $^a + $^b } ... *; #(... also equivalent to the above) -# $a and $b will always take the previous values, meaning here -# they'll start with $a = 1 and $b = 1 (values we set by hand). -# then $a = 1 and $b = 2 (result from previous $a+$b), and so on. +## $a and $b will always take the previous values, meaning here +## they'll start with $a = 1 and $b = 1 (values we set by hand). +## then $a = 1 and $b = 2 (result from previous $a+$b), and so on. say @fib[^10]; #=> 1 1 2 3 5 8 13 21 34 55 # (using a range as the index) -# Note : as for ranges, once reified, elements aren't re-calculated. -# That's why `@primes[^100]` will take a long time the first time you print -# it, then be instant. +## Note : as for ranges, once reified, elements aren't re-calculated. +## That's why `@primes[^100]` will take a long time the first time you print +## it, then be instant. ``` ## Regular Expressions ```perl6 -# I'm sure a lot of you have been waiting for this one. -# Well, now that you know a good deal of Perl 6 already, we can get started. -# First off, you'll have to forget about "PCRE regexps" (perl-compatible regexps). -# -# IMPORTANT: Don't skip them because you know PCRE. They're different. -# Some things are the same (like `?`, `+`, and `*`), -# but sometimes the semantics change (`|`). -# Make sure you read carefully, because you might trip over a new behavior. -# -# Perl 6 has many features related to RegExps. After all, Rakudo parses itself. -# We're first going to look at the syntax itself, -# then talk about grammars (PEG-like), differences between -# `token`, `regex` and `rule` declarators, and some more. -# Side note: you still have access to PCRE regexps using the `:P5` modifier. -# (we won't be discussing this in this tutorial, however) -# -# In essence, Perl 6 natively implements PEG ("Parsing Expression Grammars"). -# The pecking order for ambiguous parses is determined by a multi-level -# tie-breaking test: -# - Longest token matching. `foo\s+` beats `foo` (by 2 or more positions) -# - Longest literal prefix. `food\w*` beats `foo\w*` (by 1) -# - Declaration from most-derived to less derived grammars -# (grammars are actually classes) -# - Earliest declaration wins +## I'm sure a lot of you have been waiting for this one. +## Well, now that you know a good deal of Perl 6 already, we can get started. +## First off, you'll have to forget about "PCRE regexps" (perl-compatible +## regexps). +## +## IMPORTANT: Don't skip them because you know PCRE. They're different. +## Some things are the same (like `?`, `+`, and `*`), +## but sometimes the semantics change (`|`). +## Make sure you read carefully, because you might trip over a new behavior. +## +## Perl 6 has many features related to RegExps. After all, Rakudo parses itself. +## We're first going to look at the syntax itself, +## then talk about grammars (PEG-like), differences between +## `token`, `regex` and `rule` declarators, and some more. +## Side note: you still have access to PCRE regexps using the `:P5` modifier. +## (we won't be discussing this in this tutorial, however) +## +## In essence, Perl 6 natively implements PEG ("Parsing Expression Grammars"). +## The pecking order for ambiguous parses is determined by a multi-level +## tie-breaking test: +## - Longest token matching. `foo\s+` beats `foo` (by 2 or more positions) +## - Longest literal prefix. `food\w*` beats `foo\w*` (by 1) +## - Declaration from most-derived to less derived grammars +## (grammars are actually classes) +## - Earliest declaration wins say so 'a' ~~ /a/; #=> True say so 'a' ~~ / a /; #=> True # More readable with some spaces! -# In all our examples, we're going to use the smart-matching operator against -# a regexp. We're converting the result using `so`, but in fact, it's -# returning a `Match` object. They know how to respond to list indexing, -# hash indexing, and return the matched string. -# The results of the match are available as `$/` (implicitly lexically-scoped). -# You can also use the capture variables which start at 0: -# `$0`, `$1', `$2`... -# -# You can also note that `~~` does not perform start/end checking -# (meaning the regexp can be matched with just one char of the string), -# we're going to explain later how you can do it. - -# In Perl 6, you can have any alphanumeric as a literal, -# everything else has to be escaped, using a backslash or quotes. -say so 'a|b' ~~ / a '|' b /; # `True`. Wouldn't mean the same if `|` wasn't escaped -say so 'a|b' ~~ / a \| b /; # `True`. Another way to escape it. - -# The whitespace in a regexp is actually not significant, -# unless you use the `:s` (`:sigspace`, significant space) adverb. +## In all our examples, we're going to use the smart-matching operator against +## a regexp. We're converting the result using `so`, but in fact, it's +## returning a `Match` object. They know how to respond to list indexing, +## hash indexing, and return the matched string. +## The results of the match are available as `$/` (implicitly lexically-scoped). +## You can also use the capture variables which start at 0: +## `$0`, `$1', `$2`... +## +## You can also note that `~~` does not perform start/end checking +## (meaning the regexp can be matched with just one char of the string), +## we're going to explain later how you can do it. + +## In Perl 6, you can have any alphanumeric as a literal, +## everything else has to be escaped, using a backslash or quotes. +say so 'a|b' ~~ / a '|' b /; # `True`. Wouldn't mean the same if `|` wasn't + # escaped +say so 'a|b' ~~ / a \| b /; # `True`. Another way to escape it. + +## The whitespace in a regexp is actually not significant, +## unless you use the `:s` (`:sigspace`, significant space) adverb. say so 'a b c' ~~ / a b c /; #> `False`. Space is not significant here say so 'a b c' ~~ /:s a b c /; #> `True`. We added the modifier `:s` here. -# If we use only one space between strings in a regex, Perl 6 will warn us: -say so 'a b c' ~~ / a b c /; #> 'False' #> Space is not significant here; please -# use quotes or :s (:sigspace) modifier (or, to suppress this warning, omit the -# space, or otherwise change the spacing) -# To fix this and make the spaces less ambiguous, either use at least two -# spaces between strings or use the `:s` adverb. - -# As we saw before, we can embed the `:s` inside the slash delimiters, but we can -# also put it outside of them if we specify `m` for 'match': +## If we use only one space between strings in a regex, Perl 6 will warn us: +say so 'a b c' ~~ / a b c /; #> 'False' #> Space is not significant here; +## please use quotes or :s (:sigspace) modifier (or, to suppress this warning, +## omit the space, or otherwise change the spacing) +## To fix this and make the spaces less ambiguous, either use at least two +## spaces between strings or use the `:s` adverb. + +## As we saw before, we can embed the `:s` inside the slash delimiters, but we +## can also put it outside of them if we specify `m` for 'match': say so 'a b c' ~~ m:s/a b c/; #> `True` -# By using `m` to specify 'match' we can also use delimiters other than slashes: +## By using `m` to specify 'match', we can also use delimiters other +## than slashes: say so 'abc' ~~ m{a b c}; #> `True` -# Use the :i adverb to specify case insensitivity: + +## Use the :i adverb to specify case insensitivity: say so 'ABC' ~~ m:i{a b c}; #> `True` -# It is, however, important as for how modifiers (that you're gonna see just below) -# are applied ... + +## It is, however, important as for how modifiers (that you're gonna see just +## below) are applied ... ## Quantifying - `?`, `+`, `*` and `**`. -# - `?` - 0 or 1 +## - `?` - 0 or 1 so 'ac' ~~ / a b c /; # `False` so 'ac' ~~ / a b? c /; # `True`, the "b" matched 0 times. so 'abc' ~~ / a b? c /; # `True`, the "b" matched 1 time. -# ... As you read just before, whitespace is important because it determines -# which part of the regexp is the target of the modifier: +## ... As you read just before, whitespace is important because it determines +## which part of the regexp is the target of the modifier: so 'def' ~~ / a b c? /; # `False`. Only the `c` is optional so 'def' ~~ / a b? c /; # `False`. Whitespace is not significant so 'def' ~~ / 'abc'? /; # `True`. The whole "abc" group is optional. -# Here (and below) the quantifier applies only to the `b` +## Here (and below) the quantifier applies only to the `b` -# - `+` - 1 or more +## - `+` - 1 or more so 'ac' ~~ / a b+ c /; # `False`; `+` wants at least one matching so 'abc' ~~ / a b+ c /; # `True`; one is enough so 'abbbbc' ~~ / a b+ c /; # `True`, matched 4 "b"s -# - `*` - 0 or more +## - `*` - 0 or more so 'ac' ~~ / a b* c /; # `True`, they're all optional. so 'abc' ~~ / a b* c /; # `True` so 'abbbbc' ~~ / a b* c /; # `True` so 'aec' ~~ / a b* c /; # `False`. "b"(s) are optional, not replaceable. -# - `**` - (Unbound) Quantifier -# If you squint hard enough, you might understand -# why exponentation is used for quantity. +## - `**` - (Unbound) Quantifier +## If you squint hard enough, you might understand +## why exponentation is used for quantity. so 'abc' ~~ / a b**1 c /; # `True` (exactly one time) so 'abc' ~~ / a b**1..3 c /; # `True` (one to three times) so 'abbbc' ~~ / a b**1..3 c /; # `True` so 'abbbbbbc' ~~ / a b**1..3 c /; # `False` (too much) so 'abbbbbbc' ~~ / a b**3..* c /; # `True` (infinite ranges are okay) -# - `<[]>` - Character classes -# Character classes are the equivalent of PCRE's `[]` classes, but -# they use a more perl6-ish syntax: +## - `<[]>` - Character classes +## Character classes are the equivalent of PCRE's `[]` classes, but +## they use a more perl6-ish syntax: say 'fooa' ~~ / f <[ o a ]>+ /; #=> 'fooa' -# You can use ranges: + +## You can use ranges: say 'aeiou' ~~ / a <[ e..w ]> /; #=> 'ae' -# Just like in normal regexes, if you want to use a special character, escape it -# (the last one is escaping a space) + +## Just like in normal regexes, if you want to use a special character, +## escape it (the last one is escaping a space) say 'he-he !' ~~ / 'he-' <[ a..z \! \ ]> + /; #=> 'he-he !' -# You'll get a warning if you put duplicate names -# (which has the nice effect of catching the wrote quoting:) -'he he' ~~ / <[ h e ' ' ]> /; # Warns "Repeated characters found in characters class" -# You can also negate them ... (equivalent to `[^]` in PCRE) +## You'll get a warning if you put duplicate names +## (which has the nice effect of catching the wrote quoting:) +'he he' ~~ / <[ h e ' ' ]> /; # Warns "Repeated characters found in characters + # class" + +## You can also negate them ... (equivalent to `[^]` in PCRE) so 'foo' ~~ / <-[ f o ]> + /; # False -# ... and compose them: : -so 'foo' ~~ / <[ a..z ] - [ f o ]> + /; # False (any letter except f and o) -so 'foo' ~~ / <-[ a..z ] + [ f o ]> + /; # True (no letter except f and o) -so 'foo!' ~~ / <-[ a..z ] + [ f o ]> + /; # True (the + doesn't replace the left part) +## ... and compose them: : +so 'foo' ~~ / <[ a..z ] - [ f o ]> + /; # False (any letter except f and o) +so 'foo' ~~ / <-[ a..z ] + [ f o ]> + /; # True (no letter except f and o) +so 'foo!' ~~ / <-[ a..z ] + [ f o ]> + /; # True (the + doesn't replace the + # left part) ``` ### Grouping and capturing ```perl6 -# Group: you can group parts of your regexp with `[]`. -# These groups are *not* captured (like PCRE's `(?:)`). +## Group: you can group parts of your regexp with `[]`. +## These groups are *not* captured (like PCRE's `(?:)`). so 'abc' ~~ / a [ b ] c /; # `True`. The grouping does pretty much nothing so 'foo012012bar' ~~ / foo [ '01' <[0..9]> ] + bar /; -# The previous line returns `True`. -# We match the "012" 1 or more time (the `+` was applied to the group). - -# But this does not go far enough, because we can't actually get back what -# we matched. -# Capture: We can actually *capture* the results of the regexp, using parentheses. -so 'fooABCABCbar' ~~ / foo ( 'A' <[A..Z]> 'C' ) + bar /; # `True`. (using `so` here, `$/` below) - -# So, starting with the grouping explanations. -# As we said before, our `Match` object is available as `$/`: -say $/; # Will print some weird stuff (we'll explain) (or "Nil" if nothing matched). - -# As we also said before, it has array indexing: +## The previous line returns `True`. +## We match the "012" 1 or more time (the `+` was applied to the group). + +## But this does not go far enough, because we can't actually get back what +## we matched. +## Capture: We can actually *capture* the results of the regexp, +## using parentheses. +so 'fooABCABCbar' ~~ / foo ( 'A' <[A..Z]> 'C' ) + bar /; # `True`. (using `so` + # here, `$/` below) + +## So, starting with the grouping explanations. +## As we said before, our `Match` object is available as `$/`: +say $/; # Will print some weird stuff (we'll explain) (or "Nil" if + # nothing matched). + +## As we also said before, it has array indexing: say $/[0]; #=> ｢ABC｣ ｢ABC｣ # These weird brackets are `Match` objects. # Here, we have an array of these. say $0; # The same as above. -# Our capture is `$0` because it's the first and only one capture in the regexp. -# You might be wondering why it's an array, and the answer is simple: -# Some capture (indexed using `$0`, `$/[0]` or a named one) will be an array -# IFF it can have more than one element -# (so, with `*`, `+` and `**` (whatever the operands), but not with `?`). -# Let's use examples to see that: +## Our capture is `$0` because it's the first and only one capture in the +## regexp. You might be wondering why it's an array, and the answer is simple: +## Some capture (indexed using `$0`, `$/[0]` or a named one) will be an array +## IFF it can have more than one element +## (so, with `*`, `+` and `**` (whatever the operands), but not with `?`). +## Let's use examples to see that: -# Note: We quoted A B C to demonstrate that the whitespace between them isn't significant. -# If we want the whitespace to *be* significant there, we can use the :sigspace modifier. +## Note: We quoted A B C to demonstrate that the whitespace between them isn't +## significant. If we want the whitespace to *be* significant there, we +## can use the :sigspace modifier. so 'fooABCbar' ~~ / foo ( "A" "B" "C" )? bar /; # `True` say $/[0]; #=> ｢ABC｣ say $0.WHAT; #=> (Match) @@ -1571,16 +1597,16 @@ say $0.WHAT; #=> (Array) # A specific quantifier will always capture an Array, # may it be a range or a specific value (even 1). -# The captures are indexed per nesting. This means a group in a group will be nested -# under its parent group: `$/[0][0]`, for this code: +## The captures are indexed per nesting. This means a group in a group will be +## nested under its parent group: `$/[0][0]`, for this code: 'hello-~-world' ~~ / ( 'hello' ( <[ \- \~ ]> + ) ) 'world' /; say $/[0].Str; #=> hello~ say $/[0][0].Str; #=> ~ -# This stems from a very simple fact: `$/` does not contain strings, integers or arrays, -# it only contains match objects. These contain the `.list`, `.hash` and `.Str` methods. -# (but you can also just use `match` for hash access -# and `match[idx]` for array access) +## This stems from a very simple fact: `$/` does not contain strings, integers +## or arrays, it only contains match objects. These contain the `.list`, `.hash` +## and `.Str` methods. (but you can also just use `match` for hash access +## and `match[idx]` for array access) say $/[0].list.perl; #=> (Match.new(...),).list # We can see it's a list of Match objects. Those contain # a bunch of infos: where the match started/ended, @@ -1588,82 +1614,84 @@ say $/[0].list.perl; #=> (Match.new(...),).list # You'll see named capture below with grammars. ## Alternatives - the `or` of regexps -# WARNING: They are DIFFERENT from PCRE regexps. +## WARNING: They are DIFFERENT from PCRE regexps. so 'abc' ~~ / a [ b | y ] c /; # `True`. Either "b" or "y". so 'ayc' ~~ / a [ b | y ] c /; # `True`. Obviously enough ... -# The difference between this `|` and the one you're used to is LTM. -# LTM means "Longest Token Matching". This means that the engine will always -# try to match as much as possible in the strng +## The difference between this `|` and the one you're used to is LTM. +## LTM means "Longest Token Matching". This means that the engine will always +## try to match as much as possible in the strng 'foo' ~~ / fo | foo /; # `foo`, because it's longer. -# To decide which part is the "longest", it first splits the regex in two parts: -# The "declarative prefix" (the part that can be statically analyzed) -# and the procedural parts. -# Declarative prefixes include alternations (`|`), conjunctions (`&`), -# sub-rule calls (not yet introduced), literals, characters classes and quantifiers. -# The latter include everything else: back-references, code assertions, -# and other things that can't traditionnaly be represented by normal regexps. -# -# Then, all the alternatives are tried at once, and the longest wins. -# Examples: -# DECLARATIVE | PROCEDURAL +## To decide which part is the "longest", it first splits the regex in +## two parts: +## The "declarative prefix" (the part that can be statically analyzed) +## and the procedural parts. +## Declarative prefixes include alternations (`|`), conjunctions (`&`), +## sub-rule calls (not yet introduced), literals, characters classes and +## quantifiers. +## The latter include everything else: back-references, code assertions, +## and other things that can't traditionnaly be represented by normal regexps. +## +## Then, all the alternatives are tried at once, and the longest wins. +## Examples: +## DECLARATIVE | PROCEDURAL / 'foo' \d+ [ || ] /; -# DECLARATIVE (nested groups are not a problem) +## DECLARATIVE (nested groups are not a problem) / \s* [ \w & b ] [ c | d ] /; -# However, closures and recursion (of named regexps) are procedural. -# ... There are also more complicated rules, like specificity -# (literals win over character classes) +## However, closures and recursion (of named regexps) are procedural. +## ... There are also more complicated rules, like specificity +## (literals win over character classes) -# Note: the first-matching `or` still exists, but is now spelled `||` +## Note: the first-matching `or` still exists, but is now spelled `||` 'foo' ~~ / fo || foo /; # `fo` now. ``` ## Extra: the MAIN subroutine ```perl6 -# The `MAIN` subroutine is called when you run a Perl 6 file directly. -# It's very powerful, because Perl 6 actually parses the arguments -# and pass them as such to the sub. It also handles named argument (`--foo`) -# and will even go as far as to autogenerate a `--help` +## The `MAIN` subroutine is called when you run a Perl 6 file directly. +## It's very powerful, because Perl 6 actually parses the arguments +## and pass them as such to the sub. It also handles named argument (`--foo`) +## and will even go as far as to autogenerate a `--help` sub MAIN($name) { say "Hello, $name !" } -# This produces: -# $ perl6 cli.pl -# Usage: -# t.pl - -# And since it's a regular Perl 6 sub, you can haz multi-dispatch: -# (using a "Bool" for the named argument so that we can do `--replace` -# instead of `--replace=1`) +## This produces: +## $ perl6 cli.pl +## Usage: +## t.pl + +## And since it's a regular Perl 6 sub, you can haz multi-dispatch: +## (using a "Bool" for the named argument so that we can do `--replace` +## instead of `--replace=1`) subset File of Str where *.IO.d; # convert to IO object to check the file exists multi MAIN('add', $key, $value, Bool :$replace) { ... } multi MAIN('remove', $key) { ... } multi MAIN('import', File, Str :$as) { ... } # omitting parameter name -# This produces: -# $ perl6 cli.pl -# Usage: -# t.pl [--replace] add -# t.pl remove -# t.pl [--as=] import (File) -# As you can see, this is *very* powerful. -# It even went as far as to show inline the constants. -# (the type is only displayed if the argument is `$`/is named) +## This produces: +## $ perl6 cli.pl +## Usage: +## t.pl [--replace] add +## t.pl remove +## t.pl [--as=] import (File) +## As you can see, this is *very* powerful. +## It even went as far as to show inline the constants. +## (the type is only displayed if the argument is `$`/is named) ``` ## APPENDIX A: ### List of things ```perl6 -# It's considered by now you know the Perl6 basics. -# This section is just here to list some common operations, -# but which are not in the "main part" of the tutorial to bloat it up +## It's considered by now you know the Perl6 basics. +## This section is just here to list some common operations, +## but which are not in the "main part" of the tutorial to bloat it up ## Operators ## * Sort comparison -# They return one value of the `Order` enum : `Less`, `Same` and `More` -# (which numerify to -1, 0 or +1). +## They return one value of the `Order` enum : `Less`, `Same` and `More` +## (which numerify to -1, 0 or +1). 1 <=> 4; # sort comparison for numerics 'a' leg 'b'; # sort comparison for string $obj eqv $obj2; # sort comparison using eqv semantics @@ -1673,20 +1701,20 @@ $obj eqv $obj2; # sort comparison using eqv semantics 'b' after 'a'; # True ## * Short-circuit default operator -# Like `or` and `||`, but instead returns the first *defined* value : +## Like `or` and `||`, but instead returns the first *defined* value : say Any // Nil // 0 // 5; #=> 0 ## * Short-circuit exclusive or (XOR) -# Returns `True` if one (and only one) of its arguments is true +## Returns `True` if one (and only one) of its arguments is true say True ^^ False; #=> True ## * Flip Flop -# The flip flop operators (`ff` and `fff`, equivalent to P5's `..`/`...`). -# are operators that take two predicates to test: -# They are `False` until their left side returns `True`, then are `True` until -# their right side returns `True`. -# Like for ranges, you can exclude the iteration when it became `True`/`False` -# by using `^` on either side. -# Let's start with an example : +## The flip flop operators (`ff` and `fff`, equivalent to P5's `..`/`...`). +## are operators that take two predicates to test: +## They are `False` until their left side returns `True`, then are `True` until +## their right side returns `True`. +## Like for ranges, you can exclude the iteration when it became `True`/`False` +## by using `^` on either side. +## Let's start with an example : for { # by default, `ff`/`fff` smart-match (`~~`) against `$_`: if 'met' ^ff 'meet' { # Won't enter the if for "met" @@ -1698,35 +1726,36 @@ for { say "This ... probably will never run ..."; } } -# This will print "young hero we shall meet" (excluding "met"): -# the flip-flop will start returning `True` when it first encounters "met" -# (but will still return `False` for "met" itself, due to the leading `^` -# on `ff`), until it sees "meet", which is when it'll start returning `False`. - -# The difference between `ff` (awk-style) and `fff` (sed-style) is that -# `ff` will test its right side right when its left side changes to `True`, -# and can get back to `False` right away -# (*except* it'll be `True` for the iteration that matched) - -# While `fff` will wait for the next iteration to -# try its right side, once its left side changed: +## This will print "young hero we shall meet" (excluding "met"): +## the flip-flop will start returning `True` when it first encounters "met" +## (but will still return `False` for "met" itself, due to the leading `^` +## on `ff`), until it sees "meet", which is when it'll start returning `False`. + +## The difference between `ff` (awk-style) and `fff` (sed-style) is that +## `ff` will test its right side right when its left side changes to `True`, +## and can get back to `False` right away +## (*except* it'll be `True` for the iteration that matched) - +## While `fff` will wait for the next iteration to +## try its right side, once its left side changed: .say if 'B' ff 'B' for ; #=> B B # because the right-hand-side was tested # directly (and returned `True`). - # "B"s are printed since it matched that time - # (it just went back to `False` right away). + # "B"s are printed since it matched that + # time (it just went back to `False` + # right away). .say if 'B' fff 'B' for ; #=> B C B # The right-hand-side wasn't tested until # `$_` became "C" # (and thus did not match instantly). -# A flip-flop can change state as many times as needed: +## A flip-flop can change state as many times as needed: for { .say if $_ eq 'start' ^ff^ $_ eq 'stop'; # exclude both "start" and "stop", #=> "print it print again" } -# you might also use a Whatever Star, -# which is equivalent to `True` for the left side or `False` for the right: +## You might also use a Whatever Star, +## which is equivalent to `True` for the left side or `False` for the right: for (1, 3, 60, 3, 40, 60) { # Note: the parenthesis are superfluous here # (sometimes called "superstitious parentheses") .say if $_ > 50 ff *; # Once the flip-flop reaches a number greater than 50, @@ -1734,8 +1763,8 @@ for (1, 3, 60, 3, 40, 60) { # Note: the parenthesis are superfluous here #=> 60 3 40 60 } -# You can also use this property to create an `If` -# that'll not go through the first time : +## You can also use this property to create an `If` +## that'll not go through the first time : for { .say if * ^ff *; # the flip-flop is `True` and never goes back to `False`, # but the `^` makes it *not run* on the first iteration @@ -1743,8 +1772,8 @@ for { } -# - `===` is value identity and uses `.WHICH` on the objects to compare them -# - `=:=` is container identity and uses `VAR()` on the objects to compare them +## - `===` is value identity and uses `.WHICH` on the objects to compare them +## - `=:=` is container identity and uses `VAR()` on the objects to compare them ``` @@ -1760,6 +1789,11 @@ If you want to go further, you can: This information may be a bit older but there are many great examples and explanations. Posts stopped at the end of 2015 when the language was declared stable and Perl 6.c was released. - - Come along on `#perl6` at `irc.freenode.net`. The folks here are always helpful. - - Check the [source of Perl 6's functions and classes](https://github.com/rakudo/rakudo/tree/nom/src/core). Rakudo is mainly written in Perl 6 (with a lot of NQP, "Not Quite Perl", a Perl 6 subset easier to implement and optimize). - - Read [the language design documents](http://design.perl6.org). They explain P6 from an implementor point-of-view, but it's still very interesting. + - Come along on `#perl6` at `irc.freenode.net`. The folks here are + always helpful. + - Check the [source of Perl 6's functions and + classes](https://github.com/rakudo/rakudo/tree/nom/src/core). Rakudo is + mainly written in Perl 6 (with a lot of NQP, "Not Quite Perl", a Perl 6 subset + easier to implement and optimize). + - Read [the language design documents](http://design.perl6.org). They explain + P6 from an implementor point-of-view, but it's still very interesting. -- cgit v1.2.3 From 11e12b93fb9af08550da7245075290d36e05cec3 Mon Sep 17 00:00:00 2001 From: Bulat Musin <9249387+bmusin@users.noreply.github.com> Date: Thu, 18 Jan 2018 07:51:46 +0300 Subject: fix typo --- perl6.html.markdown | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'perl6.html.markdown') diff --git a/perl6.html.markdown b/perl6.html.markdown index 2821f0d4..4723a55f 100644 --- a/perl6.html.markdown +++ b/perl6.html.markdown @@ -1366,7 +1366,7 @@ sub add($a, $b) { $a + $b } say [[&add]] 1, 2, 3; #=> 6 ## * Zip meta-operator -## This one is an infix meta-operator than also can be used as a "normal" +## This one is an infix meta-operator that also can be used as a "normal" ## operator. It takes an optional binary function (by default, it just creates ## a pair), and will pop one value off of each array and call its binary ## function on these until it runs out of elements. It returns an array with -- cgit v1.2.3 From 654e0052915aadd897f01ddc6e0efc59446aeb10 Mon Sep 17 00:00:00 2001 From: Bulat Musin <9249387+bmusin@users.noreply.github.com> Date: Thu, 18 Jan 2018 09:31:56 +0300 Subject: [perl6/en]: fix spelling --- perl6.html.markdown | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'perl6.html.markdown') diff --git a/perl6.html.markdown b/perl6.html.markdown index 2821f0d4..7da24951 100644 --- a/perl6.html.markdown +++ b/perl6.html.markdown @@ -1659,7 +1659,7 @@ sub MAIN($name) { say "Hello, $name !" } ## Usage: ## t.pl -## And since it's a regular Perl 6 sub, you can haz multi-dispatch: +## And since it's a regular Perl 6 sub, you can have multi-dispatch: ## (using a "Bool" for the named argument so that we can do `--replace` ## instead of `--replace=1`) subset File of Str where *.IO.d; # convert to IO object to check the file exists -- cgit v1.2.3 From 677ab0252bc99f06826d79d96f7c3312cfa577d9 Mon Sep 17 00:00:00 2001 From: Martin Kimmerle Date: Thu, 15 Nov 2018 10:46:14 +0000 Subject: [fix] perl6: $n -> $m --- perl6.html.markdown | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'perl6.html.markdown') diff --git a/perl6.html.markdown b/perl6.html.markdown index 04f9c6e3..7c776db4 100644 --- a/perl6.html.markdown +++ b/perl6.html.markdown @@ -246,7 +246,7 @@ sub mutate($n is rw) { } my $m = 42; -mutate $m; # $n is now 43 ! +mutate $m; # $m is now 43 ! ## This works because we are passing the container $m to mutate. If we try ## to just pass a number instead of passing a variable it won't work because -- cgit v1.2.3 From fadf0fc0c112ad785a14c574a97c29a0db7a3f7f Mon Sep 17 00:00:00 2001 From: "Luis F. Uceta" Date: Wed, 19 Dec 2018 17:15:21 -0500 Subject: Add some changes - format consistently - remove whitespace - add example(s) - fix typos --- perl6.html.markdown | 2069 ++++++++++++++++++++++++++++----------------------- 1 file changed, 1118 insertions(+), 951 deletions(-) (limited to 'perl6.html.markdown') diff --git a/perl6.html.markdown b/perl6.html.markdown index 7c776db4..cb64b646 100644 --- a/perl6.html.markdown +++ b/perl6.html.markdown @@ -13,24 +13,28 @@ least the next hundred years. The primary Perl 6 compiler is called [Rakudo](http://rakudo.org), which runs on the JVM and [the MoarVM](http://moarvm.com). -Meta-note : double pound signs (##) are used to indicate paragraphs, while -single pound signs (#) indicate notes. +Meta-note: double pound signs (`##`) are used to indicate paragraphs, +while single pound signs (`#`) indicate notes. `#=>` represents the output of a command. ```perl6 -# Single line comment start with a pound +# Single line comments start with a pound sign. -#`( - Multiline comments use #` and a quoting construct. +#`( Multiline comments use #` and a quoting construct. (), [], {}, 「」, etc, will work. ) + +# Use the same syntax for multiline comments to embed comments. +for #`(each element in) @array { + put #`(or print element) $_ #`(with newline); +} ``` ## Variables ```perl6 -## In Perl 6, you declare a lexical variable using `my` +## In Perl 6, you declare a lexical variable using the `my` keyword: my $variable; ## Perl 6 has 3 basic types of variables: scalars, arrays, and hashes. ``` @@ -38,79 +42,81 @@ my $variable; ### Scalars ```perl6 -# Scalars represent a single value. They start with a `$` - +# Scalars represent a single value. They start with the `$` sigil: my $str = 'String'; -# double quotes allow for interpolation (which we'll see later): + +# Double quotes allow for interpolation (which we'll see later): my $str2 = "String"; ## Variable names can contain but not end with simple quotes and dashes, -## and can contain (and end with) underscores : -my $weird'variable-name_ = 5; # works ! +## and can contain (and end with) underscores: +my $person's-belongings = 'towel'; # this works! -my $bool = True; # `True` and `False` are Perl 6's boolean values. -my $inverse = !$bool; # You can invert a bool with the prefix `!` operator -my $forced-bool = so $str; # And you can use the prefix `so` operator - # which turns its operand into a Bool +my $bool = True; # `True` and `False` are Perl 6's boolean values. +my $inverse = !$bool; # Invert a bool with the prefix `!` operator. +my $forced-bool = so $str; # And you can use the prefix `so` operator +$forced-bool = ?$str; # to turn its operand into a Bool. Or use `?`. ``` ### Arrays and Lists ```perl6 -## Arrays represent multiple values. Their name start with `@`. -## Lists are similar but are an immutable type. +## Arrays represent multiple values. An array variable starts with the `@` +## sigil. Unlike lists, from which arrays inherit, arrays are mutable. my @array = 'a', 'b', 'c'; -# equivalent to : +# equivalent to: my @letters = ; # array of words, delimited by space. # Similar to perl5's qw, or Ruby's %w. -my @array = 1, 2, 3; +@array = 1, 2, 3; -say @array[2]; # Array indices start at 0 -- This is the third element +say @array[2]; # Array indices start at 0. Here the third element + # is being accessed. -say "Interpolate all elements of an array using [] : @array[]"; -#=> Interpolate all elements of an array using [] : 1 2 3 +say "Interpolate an array using []: @array[]"; +#=> Interpolate an array using []: 1 2 3 -@array[0] = -1; # Assign a new value to an array index -@array[0, 1] = 5, 6; # Assign multiple values +@array[0] = -1; # Assigning a new value to an array index +@array[0, 1] = 5, 6; # Assigning multiple values my @keys = 0, 2; @array[@keys] = @letters; # Assignment using an array containing index values -say @array; #=> a 6 b +say @array; #=> a 6 b ``` ### Hashes, or key-value Pairs. ```perl6 -## Hashes are pairs of keys and values. -## You can construct a Pair object using the syntax `Key => Value`. -## Hash tables are very fast for lookup, and are stored unordered. -## Keep in mind that keys get "flattened" in hash context, and any duplicated -## keys are deduplicated. -my %hash = 1 => 2, - 3 => 4; -my %hash = foo => "bar", # keys get auto-quoted - "some other" => "value", # trailing commas are okay - ; +## Hashes are pairs of keys and values. You can construct a `Pair` object +## using the syntax `Key => Value`. Hash tables are very fast for lookup, +## and are stored unordered. Keep in mind that keys get "flattened" in hash +## context, and any duplicated keys are deduplicated. +my %hash = 'a' => 1, 'b' => 2; + +%hash = a => 1, # keys get auto-quoted when => (fat comma) is used. + b => 2, # Trailing commas are okay. +; ## Even though hashes are internally stored differently than arrays, ## Perl 6 allows you to easily create a hash from an even numbered array: -my %hash = ; - -my %hash = key1 => 'value1', key2 => 'value2'; # same result as above - -## You can also use the "colon pair" syntax: -## (especially handy for named parameters that you'll see later) -my %hash = :w(1), # equivalent to `w => 1` - # this is useful for the `True` shortcut: - :truey, # equivalent to `:truey(True)`, or `truey => True` - # and for the `False` one: - :!falsey, # equivalent to `:falsey(False)`, or `falsey => False` - ; - -say %hash{'key1'}; # You can use {} to get the value from a key -say %hash; # If it's a string, you can actually use <> - # (`{key1}` doesn't work, as Perl6 doesn't have barewords) +%hash = ; # Or: +%hash = "key1", "value1", "key2", "value2"; + +%hash = key1 => 'value1', key2 => 'value2'; # same result as above + +## You can also use the "colon pair" syntax. This syntax is especially +## handy for named parameters that you'll see later. +%hash = :w(1), # equivalent to `w => 1` + :truey, # equivalent to `:truey(True)` or `truey => True` + :!falsey, # equivalent to `:falsey(False)` or `falsey => False` +; +## The :truey and :!falsey constructs are known as the +## `True` and `False` shortcuts respectively. + +say %hash{'key1'}; # You can use {} to get the value from a key. +say %hash; # If it's a string without spaces, you can actually use + # <> (quote-words operator). `{key1}` doesn't work, + # as Perl6 doesn't have barewords. ``` ## Subs @@ -120,112 +126,112 @@ say %hash; # If it's a string, you can actually use <> ## created with the `sub` keyword. sub say-hello { say "Hello, world" } -## You can provide (typed) arguments. -## If specified, the type will be checked at compile-time if possible, -## otherwise at runtime. -sub say-hello-to(Str $name) { +## You can provide (typed) arguments. If specified, the type will be checked +## at compile-time if possible, otherwise at runtime. +sub say-hello-to( Str $name ) { say "Hello, $name !"; } -## A sub returns the last value of the block. -sub return-value { - 5; -} -say return-value; # prints 5 -sub return-empty { -} -say return-empty; # prints Nil +## A sub returns the last value of the block. Similarly, the semicolon in +## the last can be omitted. +sub return-value { 5 } +say return-value; # prints 5 -## Some control flow structures produce a value, like if: +sub return-empty { } +say return-empty; # prints Nil + +## Some control flow structures produce a value, like `if`: sub return-if { - if True { - "Truthy"; - } + if True { "Truthy" } } -say return-if; # prints Truthy +say return-if; # prints Truthy -## Some don't, like for: +## Some don't, like `for`: sub return-for { - for 1, 2, 3 { } + for 1, 2, 3 { 'Hi' } } -say return-for; # prints Nil +say return-for; # prints Nil -## A sub can have optional arguments: -sub with-optional($arg?) { # the "?" marks the argument optional - say "I might return `(Any)` (Perl's 'null'-like value) if I don't have - an argument passed, or I'll return my argument"; +## Positional arguments are required by default. To make them optional, use +## the `?` after the parameters' names. +sub with-optional( $arg? ) { + # This sub returns `(Any)` (Perl's null-like value) if + # no argument is passed. Otherwise, it returns its argument. $arg; } -with-optional; # returns Any -with-optional(); # returns Any -with-optional(1); # returns 1 +with-optional; # returns Any +with-optional(); # returns Any +with-optional(1); # returns 1 -## You can also give them a default value when they're not passed: -sub hello-to($name = "World") { - say "Hello, $name !"; +## You can also give them a default value when they're not passed. +## Required parameters must come before optional ones. +sub greeting( $name, $type = "Hello" ) { + say "$type, $name!"; } -hello-to; #=> Hello, World ! -hello-to(); #=> Hello, World ! -hello-to('You'); #=> Hello, You ! + +greeting("Althea"); #=> Hello, Althea! +greeting("Arthur", "Good morning"); #=> Good morning, Arthur! ## You can also, by using a syntax akin to the one of hashes -## (yay unified syntax !), pass *named* arguments to a `sub`. -## They're optional, and will default to "Any". -sub with-named($normal-arg, :$named) { - say $normal-arg + $named; +## (yay unified syntax !), pass *named* arguments to a `sub`. They're +## optional, and will default to "Any". +sub with-named( $normal-arg, :$named ) { + say $normal-arg + $named; } with-named(1, named => 6); #=> 7 -## There's one gotcha to be aware of, here: -## If you quote your key, Perl 6 won't be able to see it at compile time, -## and you'll have a single Pair object as a positional parameter, -## which means this fails: -with-named(1, 'named' => 6); -with-named(2, :named(5)); #=> 7 +## There's one gotcha to be aware of, here: If you quote your key, Perl 6 +## won't be able to see it at compile time, and you'll have a single `Pair` +## object as a positional parameter, which means +## `with-named(1, 'named' => 6);` fails. + +with-named(2, :named(5)); #=> 7 -## To make a named argument mandatory, you can use `?`'s inverse, `!` -sub with-mandatory-named(:$str!) { - say "$str !"; +## To make a named argument mandatory, you can append `!` to the parameter, +## which is the inverse of `?`: +sub with-mandatory-named( :$str! ) { + say "$str!"; } -with-mandatory-named(str => "My String"); #=> My String ! -with-mandatory-named; # run time error: "Required named parameter not passed" -with-mandatory-named(3);# run time error:"Too many positional parameters passed" +with-mandatory-named(str => "My String"); #=> My String! +with-mandatory-named; # runtime error:"Required named parameter not passed" +with-mandatory-named(3);# runtime error:"Too many positional parameters passed" -## If a sub takes a named boolean argument ... -sub takes-a-bool($name, :$bool) { - say "$name takes $bool"; +## If a sub takes a named boolean argument... +sub takes-a-bool( $name, :$bool ) { + say "$name takes $bool"; } ## ... you can use the same "short boolean" hash syntax: -takes-a-bool('config', :bool); # config takes True -takes-a-bool('config', :!bool); # config takes False +takes-a-bool('config', :bool); #=> config takes True +takes-a-bool('config', :!bool); #=> config takes False -## You can also provide your named arguments with defaults: -sub named-def(:$def = 5) { - say $def; +## You can also provide your named arguments with default values: +sub named-def( :$def = 5 ) { + say $def; } -named-def; #=> 5 +named-def; #=> 5 named-def(def => 15); #=> 15 ## Since you can omit parenthesis to call a function with no arguments, -## you need "&" in the name to store `say-hello` in a variable. +## you need `&` in the name to store `say-hello` in a variable. This means +## `&say-hello` is a code object and not a subroutine call. my &s = &say-hello; -my &other-s = sub { say "Anonymous function !" } +my &other-s = sub { say "Anonymous function!" } -## A sub can have a "slurpy" parameter, or "doesn't-matter-how-many" -sub as-many($head, *@rest) { #`*@` (slurpy) will "take everything else" -## Note: you can have parameters *before* a slurpy one (like here), -## but not *after*. - say @rest.join(' / ') ~ " !"; +## A sub can have a "slurpy" parameter, or "doesn't-matter-how-many". For +## this, you must use `*@` (slurpy) which will "take everything else". You can +## have as many parameters *before* a slurpy one, but not *after*. +sub as-many($head, *@rest) { + say @rest.join(' / ') ~ " !"; } -say as-many('Happy', 'Happy', 'Birthday'); #=> Happy / Birthday ! - # Note that the splat (the *) did not - # consume the parameter before. +say as-many('Happy', 'Happy', 'Birthday');#=> Happy / Birthday ! + # Note that the splat (the *) did not + # consume the parameter before it. -## You can call a function with an array using the -## "argument list flattening" operator `|` -## (it's not actually the only role of this operator, but it's one of them) +## You can call a function with an array using the "argument list flattening" +## operator `|` (it's not actually the only role of this operator, +## but it's one of them). sub concat3($a, $b, $c) { - say "$a, $b, $c"; + say "$a, $b, $c"; } concat3(|@array); #=> a, b, c # `@array` got "flattened" as a part of the argument list @@ -234,159 +240,188 @@ concat3(|@array); #=> a, b, c ## Containers ```perl6 -## In Perl 6, values are actually stored in "containers". -## The assignment operator asks the container on the left to store the value on -## its right. When passed around, containers are marked as immutable. -## Which means that, in a function, you'll get an error if you try to -## mutate one of your arguments. -## If you really need to, you can ask for a mutable container using `is rw`: -sub mutate($n is rw) { - $n++; - say "\$n is now $n !"; +## In Perl 6, values are actually stored in "containers". The assignment +## operator asks the container on the left to store the value on its right. +## When passed around, containers are marked as immutable which means that, +## in a function, you'll get an error if you try to mutate one of your +## arguments. If you really need to, you can ask for a mutable container by +## using the `is rw` trait: +sub mutate( $n is rw ) { + $n++; } my $m = 42; -mutate $m; # $m is now 43 ! +mutate $m; #=> 43 +say $m; #=> 43 -## This works because we are passing the container $m to mutate. If we try -## to just pass a number instead of passing a variable it won't work because -## there is no container being passed and integers are immutable by themselves: +## This works because we are passing the container $m to the `mutate` sub. +## If we try to just pass a number instead of passing a variable it won't work +## because there is no container being passed and integers are immutable by +## themselves: mutate 42; # Parameter '$n' expected a writable container, but got Int value -## If what you want a copy instead, use `is copy`. +## Similar error would be obtained, if a bound variable is passed to +## to the subroutine: + +my $v := 50; # binding 50 to the variable $v +mutate $v; # Parameter '$n' expected a writable container, but got Int value + +## If what you want is a copy instead, use the `is copy` trait which will +## cause the argument to be copied and allow you to modify the argument +## inside the routine. ## A sub itself returns a container, which means it can be marked as rw: my $x = 42; sub x-store() is rw { $x } x-store() = 52; # in this case, the parentheses are mandatory # (else Perl 6 thinks `x-store` is an identifier) -say $x; #=> 52 +say $x; #=> 52 ``` ## Control Flow Structures + ### Conditionals ```perl6 ## - `if` ## Before talking about `if`, we need to know which values are "Truthy" -## (represent True), and which are "Falsey" (or "Falsy") -- represent False. -## Only these values are Falsey: 0, (), {}, "", Nil, A type (like `Str` or -## `Int`) and of course False itself. -## Every other value is Truthy. +## (represent True), and which are "Falsey" (represent False). Only these +## values are Falsey: 0, (), {}, "", Nil, A type (like `Str` or `Int`) and +## of course False itself. Any other value is Truthy. if True { - say "It's true !"; + say "It's true!"; } unless False { - say "It's not false !"; + say "It's not false!"; } -## As you can see, you don't need parentheses around conditions. -## However, you do need the brackets around the "body" block: -# if (true) say; # This doesn't work ! +## As you can see, you don't need parentheses around conditions. However, you +## do need the curly braces around the "body" block. For example, +## `if (true) say;` doesn't work. -## You can also use their postfix versions, with the keyword after: -say "Quite truthy" if True; +## You can also use their statement modifier (postfix) versions: +say "Quite truthy" if True; #=> Quite truthy +say "Quite falsey" unless False; #=> Quite falsey -## - Ternary conditional, "?? !!" (like `x ? y : z` in some other languages) -## returns $value-if-true if the condition is true and $value-if-false -## if it is false. -## my $result = $value condition ?? $value-if-true !! $value-if-false; +## - Ternary operator, "x ?? y !! z" +## This returns $value-if-true if the condition is true and $value-if-false +## if it is false. +## my $result = condition ?? $value-if-true !! $value-if-false; my $age = 30; say $age > 18 ?? "You are an adult" !! "You are under 18"; +#=> You are an adult ``` -### given/when, or switch +### given/when, or Perl 6's switch construct ```perl6 -## - `given`-`when` looks like other languages' `switch`, but is much more +## `given...when` looks like other languages' `switch`, but is much more ## powerful thanks to smart matching and Perl 6's "topic variable", $_. ## -## This variable contains the default argument of a block, -## a loop's current iteration (unless explicitly named), etc. +## The topic variable $_ contains the default argument of a block, a loop's +## current iteration (unless explicitly named), etc. ## ## `given` simply puts its argument into `$_` (like a block would do), ## and `when` compares it using the "smart matching" (`~~`) operator. ## ## Since other Perl 6 constructs use this variable (as said before, like `for`, -## blocks, etc), this means the powerful `when` is not only applicable along +## blocks, etc), this means the powerful `when` is not only applicable along ## with a `given`, but instead anywhere a `$_` exists. given "foo bar" { - say $_; #=> foo bar - when /foo/ { # Don't worry about smart matching yet – just know `when` uses it - # This is equivalent to `if $_ ~~ /foo/`. - say "Yay !"; - } - when $_.chars > 50 { # smart matching anything with True is True, - # i.e. (`$a ~~ True`) - # so you can also put "normal" conditionals. - # This `when` is equivalent to this `if`: - # if $_ ~~ ($_.chars > 50) {...} - # Which means: - # if $_.chars > 50 {...} - say "Quite a long string !"; - } - default { # same as `when *` (using the Whatever Star) - say "Something else" - } + say $_; #=> foo bar + when /foo/ { # Don't worry about smart matching yet. Just know + say "Yay !"; # `when` uses it. This is equivalent to `if $_ ~~ /foo/`. + + } + when $_.chars > 50 { # smart matching anything with True is True, + # i.e. (`$a ~~ True`) + # so you can also put "normal" conditionals. + # This `when` is equivalent to this `if`: + # `if $_ ~~ ($_.chars > 50) {...}` + # which means: `if $_.chars > 50 {...}` + say "Quite a long string !"; + } + default { # same as `when *` (using the Whatever Star) + say "Something else" + } } ``` ### Looping constructs ```perl6 -## - `loop` is an infinite loop if you don't pass it arguments, -## but can also be a C-style `for` loop: +## - `loop` is an infinite loop if you don't pass it arguments, but can also +## be a C-style `for` loop: loop { - say "This is an infinite loop !"; - last; # last breaks out of the loop, like the `break` keyword in other - # languages + say "This is an infinite loop !"; + last; # last breaks out of the loop, like + # the `break` keyword in other languages } loop (my $i = 0; $i < 5; $i++) { - next if $i == 3; # `next` skips to the next iteration, like `continue` + next if $i == 3; # `next` skips to the next iteration, like `continue` # in other languages. Note that you can also use postfix # conditionals, loops, etc. - say "This is a C-style for loop !"; + say "This is a C-style for loop!"; } -## - `for` - Passes through an array +## - `for` - Iterating through an array + +my @array = 1, 2, 6, 7, 3; + +## Accessing the array's elements with the topic variable $_. +for @array { + say "I've got $_ !"; +} + +## Accessing the array's elements with a "pointy block", `->`. +## Here each element is read-only. for @array -> $variable { - say "I've got $variable !"; + say "I've got $variable !"; } -## As we saw with given, for's default "current iteration" variable is `$_`. -## That means you can use `when` in a `for` just like you were in a `given`. +## Accessing the array's elements with a "doubly pointy block", `<->`. +## Here each element is read-write so mutating `$variable` mutates +## that element in the array. +for @array <-> $variable { + say "I've got $variable !"; +} + +## As we saw with given, a for loop's default "current iteration" variable +## is `$_`. That means you can use `when` in a `for`loop just like you were +## able to in a `given`. for @array { - say "I've got $_"; + say "I've got $_"; - .say; # This is also allowed. - # A dot call with no "topic" (receiver) is sent to `$_` by default - $_.say; # the above and this are equivalent. + .say; # This is also allowed. A dot call with no "topic" (receiver) + # is sent to `$_` by default + $_.say; # This is equivalent to the above statement. } for @array { - # You can... - next if $_ == 3; # Skip to the next iteration (`continue` in C-like languages) - redo if $_ == 4; # Re-do the iteration, keeping the same topic variable (`$_`) - last if $_ == 5; # Or break out of a loop (like `break` in C-like languages) + # You can... + next if $_ == 3; # Skip to the next iteration (`continue` in C-like lang.) + redo if $_ == 4; # Re-do iteration, keeping the same topic variable (`$_`) + last if $_ == 5; # Or break out of loop (like `break` in C-like lang.) } -## The "pointy block" syntax isn't specific to for. -## It's just a way to express a block in Perl6. +## The "pointy block" syntax isn't specific to the `for` loop. It's just a way +## to express a block in Perl 6. +sub long-computation { "Finding factors of large primes" } if long-computation() -> $result { - say "The result is $result"; + say "The result is $result."; } ``` ## Operators ```perl6 -## Since Perl languages are very much operator-based languages, -## Perl 6 operators are actually just funny-looking subroutines, in syntactic +## Since Perl languages are very much operator-based languages, Perl 6 +## operators are actually just funny-looking subroutines, in syntactic ## categories, like infix:<+> (addition) or prefix: (bool not). ## The categories are: @@ -394,105 +429,127 @@ if long-computation() -> $result { ## - "postfix": after (like `++` in `$a++`). ## - "infix": in between (like `*` in `4 * 3`). ## - "circumfix": around (like `[`-`]` in `[1, 2]`). -## - "post-circumfix": around, after another term (like `{`-`}` in -## `%hash{'key'}`) +## - "post-circumfix": around, after another term (like `{`-`}` in +## `%hash{'key'}`) ## The associativity and precedence list are explained below. -## Alright, you're set to go ! +## Alright, you're set to go! -## * Equality Checking +## Equality Checking +##------------------ ## - `==` is numeric comparison -3 == 4; # False -3 != 4; # True +3 == 4; #=> False +3 != 4; #=> True ## - `eq` is string comparison -'a' eq 'b'; -'a' ne 'b'; # not equal -'a' !eq 'b'; # same as above +'a' eq 'b'; #=> False +'a' ne 'b'; #=> True, not equal +'a' !eq 'b'; #=> True, same as above ## - `eqv` is canonical equivalence (or "deep equality") -(1, 2) eqv (1, 3); +(1, 2) eqv (1, 3); #=> False +(1, 2) eqv (1, 2); #=> True +Int === Int #=> True -## - Smart Match Operator: `~~` +## - `~~` is the smart match operator ## Aliases the left hand side to $_ and then evaluates the right hand side. ## Here are some common comparison semantics: -## String or Numeric Equality - +## String or numeric equality 'Foo' ~~ 'Foo'; # True if strings are equal. -12.5 ~~ 12.50; # True if numbers are equal. +12.5 ~~ 12.50; # True if numbers are equal. ## Regex - For matching a regular expression against the left side. -## Returns a (Match) object, which evaluates as True if regexp matches. +## Returns a `Match` object, which evaluates as True if regexp matches. my $obj = 'abc' ~~ /a/; -say $obj; # ｢a｣ -say $obj.WHAT; # (Match) +say $obj; #=> ｢a｣ +say $obj.WHAT; #=> (Match) ## Hashes -'key' ~~ %hash; # True if key exists in hash - -## Type - Checks if left side "has type" (can check superclasses and roles) - -1 ~~ Int; # True +'key' ~~ %hash; # True if key exists in hash. -## Smart-matching against a boolean always returns that boolean (and will warn). +## Type - Checks if left side "is of type" (can check superclasses and +## roles). +say 1 ~~ Int; #=> True -1 ~~ True; # True -False ~~ True; # True +## Smart-matching against a boolean always returns that boolean +## (and will warn). +say 1 ~~ True; #=> True +say False ~~ True; #=> True -## General syntax is $arg ~~ &bool-returning-function; -## For a complete list of combinations, use this table: +## General syntax is `$arg ~~ &bool-returning-function;`. For a complete list +## of combinations, use this table: ## http://perlcabal.org/syn/S03.html#Smart_matching -## You also, of course, have `<`, `<=`, `>`, `>=`. -## Their string equivalent are also available : `lt`, `le`, `gt`, `ge`. -3 > 4; +## Of course, you also use `<`, `<=`, `>`, `>=` for numeric comparison. +## Their string equivalent are also available: `lt`, `le`, `gt`, `ge`. +3 > 4; # False +3 >= 4; # False +3 < 4; # True +3 <= 4; # True +'a' gt 'b'; # False +'a' ge 'b'; # False +'a' lt 'b'; # True +'a' le 'b'; # True + + +## Range constructor +##------------------ +3 .. 7; # 3 to 7, both included +3 ..^ 7; # 3 to 7, exclude right endpoint. +3 ^.. 7; # 3 to 7, exclude left endpoint. Same as `4..7`. +3 ^..^ 7; # 3 to 7, exclude both endpoints. Same as `4..6`. -## * Range constructors -3 .. 7; # 3 to 7, both included -## `^` on either side them exclusive on that side : -3 ^..^ 7; # 3 to 7, not included (basically `4 .. 6`) ## This also works as a shortcut for `0..^N`: -^10; # means 0..^10 +^10; # means 0..^10 ## This also allows us to demonstrate that Perl 6 has lazy/infinite arrays, ## using the Whatever Star: -my @array = 1..*; # 1 to Infinite ! `1..Inf` is the same. -say @array[^10]; # you can pass arrays as subscripts and it'll return - # an array of results. This will print - # "1 2 3 4 5 6 7 8 9 10" (and not run out of memory !) -## Note : when reading an infinite list, Perl 6 will "reify" the elements +my @array = 1..*; # 1 to Infinite! Equivalent to `1..Inf`. +say @array[^10]; # You can pass ranges as subscripts and it'll return + # an array of results. This will print + # "1 2 3 4 5 6 7 8 9 10" (and not run out of memory!) + +## Note: when reading an infinite list, Perl 6 will "reify" the elements ## it needs, then keep them in memory. They won't be calculated more than once. ## It also will never calculate more elements that are needed. -## Trying -## An array subscript can also be a closure. -## It'll be called with the length as the argument +## An array subscript can also be a closure. It'll be called with the length +## as the argument: say join(' ', @array[15..*]); #=> 15 16 17 18 19 ## which is equivalent to: say join(' ', @array[-> $n { 15..$n }]); + ## Note: if you try to do either of those with an infinite array, -## you'll trigger an infinite loop (your program won't finish) +## you'll trigger an infinite loop (your program won't finish). -## You can use that in most places you'd expect, even assigning to an array +## You can use that in most places you'd expect, even when assigning to +## an array: my @numbers = ^20; -## Here numbers increase by "6"; more on `...` operator later. -my @seq = 3, 9 ... * > 95; # 3 9 15 21 27 [...] 81 87 93 99; +## Here the numbers increase by 6, like an arithmetic sequence; more on the +## sequence (`...`) operator later. +my @seq = 3, 9 ... * > 95; # 3 9 15 21 27 [...] 81 87 93 99; @numbers[5..*] = 3, 9 ... *; # even though the sequence is infinite, # only the 15 needed values will be calculated. -say @numbers; #=> 0 1 2 3 4 3 9 15 21 [...] 81 87 - # (only 20 values) +say @numbers; #=> 0 1 2 3 4 3 9 15 21 [...] 81 87 + # (only 20 values) -## * And &&, Or || -3 && 4; # 4, which is Truthy. Calls `.Bool` on `4` and gets `True`. -0 || False; # False. Calls `.Bool` on `0` +## and (&&), or (||) +##------------------ +3 && 4; # 4, which is Truthy. Calls `.Bool` on both 3 and 4 and gets `True` + # so it returns 4 since both are `True`. +3 && 0; # 0 +0 && 4; # 0 -## * Short-circuit (and tight) versions of the above -# Returns the first argument that evaluates to False, or the last argument. +0 || False; # False. Calls `.Bool` on `0` and `False` which are both `False` + # so it retusns `False` since both are `False`. + +## Short-circuit (and tight) versions of the above +## Return the first argument that evaluates to False, or the last argument. my ( $a, $b, $c ) = 1, 0, 2; $a && $b && $c; # Returns 0, the first False value @@ -500,203 +557,242 @@ $a && $b && $c; # Returns 0, the first False value ## || Returns the first argument that evaluates to True $b || $a; # 1 -## And because you're going to want them, -## you also have compound assignment operators: -$a *= 2; # multiply and assignment. Equivalent to $a = $a * 2; -$b %%= 5; # divisible by and assignment +## And because you're going to want them, you also have compound assignment +## operators: +$a *= 2; # multiply and assignment. Equivalent to $a = $a * 2; +$b %%= 5; # divisible by and assignment. Equivalent to $b = $b %% 2; +$c div= 3; # return divisor and assignment. Equivalent to $c = $c div 3; +$d mod= 4; # return remainder and assignment. Equivalent to $d = $d mod 4; @array .= sort; # calls the `sort` method and assigns the result back ``` -## More on subs ! +## More on subs! ```perl6 -## As we said before, Perl 6 has *really* powerful subs. We're going to see -## a few more key concepts that make them better than in any other language :-). +## As we said before, Perl 6 has *really* powerful subs. We're going +## to see a few more key concepts that make them better than in any +## other language :-). ``` -### Unpacking ! +### Unpacking! ```perl6 -## It's the ability to "extract" arrays and keys (AKA "destructuring"). -## It'll work in `my`s and in parameter lists. +## Unpacking is the ability to "extract" arrays and keys +## (AKA "destructuring"). It'll work in `my`s and in parameter lists. my ($f, $g) = 1, 2; -say $f; #=> 1 -my ($, $, $h) = 1, 2, 3; # keep the non-interesting anonymous -say $h; #=> 3 +say $f; #=> 1 +my ($, $, $h) = 1, 2, 3; # keep the non-interesting values anonymous (`$`) +say $h; #=> 3 my ($head, *@tail) = 1, 2, 3; # Yes, it's the same as with "slurpy subs" my (*@small) = 1; -sub unpack_array(@array [$fst, $snd]) { - say "My first is $fst, my second is $snd ! All in all, I'm @array[]."; +sub unpack_array( @array [$fst, $snd] ) { + say "My first is $fst, my second is $snd! All in all, I'm @array[]."; # (^ remember the `[]` to interpolate the array) } -unpack_array(@tail); #=> My first is 2, my second is 3 ! All in all, I'm 2 3 +unpack_array(@tail); #=> My first is 2, my second is 3! All in all, I'm 2 3. ## If you're not using the array itself, you can also keep it anonymous, ## much like a scalar: -sub first-of-array(@ [$fst]) { $fst } +sub first-of-array( @ [$fst] ) { $fst } first-of-array(@small); #=> 1 -first-of-array(@tail); # Throws an error "Too many positional parameters passed" - # (which means the array is too big). +first-of-array(@tail); # Error: "Too many positional parameters passed" + # (which means the array is too big). -## You can also use a slurp ... +## You can also use a slurp... sub slurp-in-array(@ [$fst, *@rest]) { # You could keep `*@rest` anonymous - say $fst + @rest.elems; # `.elems` returns a list's length. - # Here, `@rest` is `(3,)`, since `$fst` holds the `2`. + say $fst + @rest.elems; # `.elems` returns a list's length. + # Here, `@rest` is `(3,)`, since `$fst` + # holds the `2`. } -slurp-in-array(@tail); #=> 3 +slurp-in-array(@tail); #=> 3 ## You could even extract on a slurpy (but it's pretty useless ;-).) -sub fst(*@ [$fst]) { # or simply : `sub fst($fst) { ... }` - say $fst; +sub fst(*@ [$fst]) { # or simply: `sub fst($fst) { ... }` + say $fst; } -fst(1); #=> 1 +fst(1); #=> 1 fst(1, 2); # errors with "Too many positional parameters passed" -## You can also destructure hashes (and classes, which you'll learn about later) -## The syntax is basically `%hash-name (:key($variable-to-store-value-in))`. +## You can also destructure hashes (and classes, which you'll learn about +## later). The syntax is basically the same as +## `%hash-name (:key($variable-to-store-value-in))`. ## The hash can stay anonymous if you only need the values you extracted. -sub key-of(% (:value($val), :qua($qua))) { - say "Got val $val, $qua times."; +sub key-of( % (:value($val), :qua($qua)) ) { + say "Got val $val, $qua times."; } -## Then call it with a hash: (you need to keep the brackets for it to be a hash) -key-of({value => 'foo', qua => 1}); +## Then call it with a hash. You need to keep the curly braces for it to be a +## hash or use `%()` instead to indicate a hash is being passed. +key-of({value => 'foo', qua => 1}); #=> Got val foo, 1 times. +key-of(%(value => 'foo', qua => 1)); #=> Got val foo, 1 times. #key-of(%hash); # the same (for an equivalent `%hash`) -## The last expression of a sub is returned automatically -## (though you may use the `return` keyword, of course): -sub next-index($n) { - $n + 1; +## The last expression of a sub is returned automatically (though you may +## indicate explicitly by using the `return` keyword, of course): +sub next-index( $n ) { + $n + 1; } my $new-n = next-index(3); # $new-n is now 4 -## This is true for everything, except for the looping constructs -## (due to performance reasons): there's reason to build a list -## if we're just going to discard all the results. -## If you still want to build one, you can use the `do` statement prefix: -## (or the `gather` prefix, which we'll see later) -sub list-of($n) { - do for ^$n { # note the use of the range-to prefix operator `^` (`0..^N`) - $_ # current loop iteration - } +## This is true for everything, except for the looping constructs (due to +## performance reasons): there's no reason to build a list if we're just going to +## discard all the results. If you still want to build one, you can use the +## `do` statement prefix or the `gather` prefix, which we'll see later: + +sub list-of( $n ) { + do for ^$n { # note the range-to prefix operator `^` (`0..^N`) + $_ # current loop iteration known as the "topic" variable + } } my @list3 = list-of(3); #=> (0, 1, 2) ``` -### lambdas +### lambdas (or anonymous subroutines) ```perl6 -## You can create a lambda with `-> {}` ("pointy block") or `{}` ("block") -my &lambda = -> $argument { "The argument passed to this lambda is $argument" } +## You can create a lambda with `-> {}` ("pointy block") , +## `{}` ("block") or `sub {}`. + +my &lambda1 = -> $argument { + "The argument passed to this lambda is $argument" +} + +my &lambda2 = { + "The argument passed to this lambda is $_" +} + +my &lambda3 = sub ($argument) { + "The argument passed to this lambda is $argument" +} + ## `-> {}` and `{}` are pretty much the same thing, except that the former can ## take arguments, and that the latter can be mistaken as a hash by the parser. -## We can, for example, add 3 to each value of an array using map: +## We can, for example, add 3 to each value of an array using the +## `map` function with a lambda: my @arrayplus3 = map({ $_ + 3 }, @array); # $_ is the implicit argument ## A sub (`sub {}`) has different semantics than a block (`{}` or `-> {}`): ## A block doesn't have a "function context" (though it can have arguments), -## which means that if you return from it, -## you're going to return from the parent function. Compare: -sub is-in(@array, $elem) { - # this will `return` out of the `is-in` sub - # once the condition evaluated to True, the loop won't be run anymore - map({ return True if $_ == $elem }, @array); -} -sub truthy-array(@array) { - # this will produce an array of `True` and `False`: - # (you can also say `anon sub` for "anonymous subroutine") - map(sub ($i) { if $i { return True } else { return False } }, @array); - # ^ the `return` only returns from the anonymous `sub` -} - -## You can also use the "whatever star" to create an anonymous function +## which means that if you return from it, you're going to return from the +## parent function. Compare: +sub is-in( @array, $elem ) { + # this will `return` out of the `is-in` sub once the condition evaluated + ## to True, the loop won't be run anymore. + map({ return True if $_ == $elem }, @array); +} +## with: +sub truthy-array( @array ) { + # this will produce an array of `True` and `False`: + # (you can also say `anon sub` for "anonymous subroutine") + map(sub ($i) { if $i { return True } else { return False } }, @array); + # ^ the `return` only returns from the anonymous `sub` +} + +## The `anon` declarator can be used to create an anonymous sub from a +## regular subroutine. The regular sub knows its name but its symbol is +## prevented from getting installed in the lexical scope, the method table +## and everywhere else. + +my $anon-sum = anon sub summation(*@a) { [+] *@a } +say $anon-sum.name; #=> summation +say $anon-sum(2, 3, 5); #=> 10 +#say summation; #=> Error: Undeclared routine: ... + +## You can also use the "whatever star" to create an anonymous subroutine. ## (it'll stop at the furthest operator in the current expression) -my @arrayplus3 = map(*+3, @array); # `*+3` is the same as `{ $_ + 3 }` +my @arrayplus3 = map(*+3, @array); # `*+3` is the same as `{ $_ + 3 }` my @arrayplus3 = map(*+*+3, @array); # Same as `-> $a, $b { $a + $b + 3 }` # also `sub ($a, $b) { $a + $b + 3 }` -say (*/2)(4); #=> 2 - # Immediately execute the function Whatever created. +say (*/2)(4); #=> 2 + # Immediately execute the function Whatever created. say ((*+3)/5)(5); #=> 1.6 - # works even in parens ! - -## But if you need to have more than one argument (`$_`) -## in a block (without wanting to resort to `-> {}`), -## you can also use the implicit argument syntax, `$^` : -map({ $^a + $^b + 3 }, @array); # equivalent to following: -map(sub ($a, $b) { $a + $b + 3 }, @array); # (here with `sub`) - -## Note : those are sorted lexicographically. -# `{ $^b / $^a }` is like `-> $a, $b { $b / $a }` + # It works even in parens! + +## But if you need to have more than one argument (`$_`) in a block (without +## wanting to resort to `-> {}`), you can also use the implicit argument +## syntax, `$^`: +map({ $^a + $^b + 3 }, @array); +# which is equivalent to the following which uses a `sub`: +map(sub ($a, $b) { $a + $b + 3 }, @array); + +## The parameters `$^a`, `$^b`, etc. are known as placeholder parameters or +## self-declared positional parameters. They're sorted lexicographically so +## `{ $^b / $^a }` is equivalent `-> $a, $b { $b / $a }`. ``` ### About types... ```perl6 -## Perl6 is gradually typed. This means you can specify the type -## of your variables/arguments/return types, or you can omit them -## and they'll default to "Any". -## You obviously get access to a few base types, like Int and Str. -## The constructs for declaring types are "class", "role", -## which you'll see later. - -## For now, let us examine "subset": -## a "subset" is a "sub-type" with additional checks. -## For example: "a very big integer is an Int that's greater than 500" -## You can specify the type you're subtyping (by default, Any), -## and add additional checks with the "where" keyword: +## Perl 6 is gradually typed. This means you can specify the type of your +## variables/arguments/return types, or you can omit the type annotations in +## in which case they'll default to `Any`. Obviously you get access to a few +## base types, like `Int` and `Str`. The constructs for declaring types are +## "subset", "class", "role", etc. which you'll see later. + +## For now, let us examine "subset" which is a "sub-type" with additional +## checks. For example, "a very big integer is an Int that's greater than 500". +## You can specify the type you're subtyping (by default, `Any`), and add +## additional checks with the `where` clause: subset VeryBigInteger of Int where * > 500; +## Or the set of the whole numbers: +subset WholeNumber of Int where * >= 0; ``` ### Multiple Dispatch ```perl6 ## Perl 6 can decide which variant of a `sub` to call based on the type of the -## arguments, or on arbitrary preconditions, like with a type or a `where`: +## arguments, or on arbitrary preconditions, like with a type or `where`: -## with types -multi sub sayit(Int $n) { # note the `multi` keyword here +## with types: +multi sub sayit( Int $n ) { # note the `multi` keyword here say "Number: $n"; } -multi sayit(Str $s) { # a multi is a `sub` by default +multi sayit( Str $s ) { # a multi is a `sub` by default say "String: $s"; } -sayit("foo"); # prints "String: foo" -sayit(True); # fails at *compile time* with - # "calling 'sayit' will never work with arguments of types ..." +sayit("foo"); #=> "String: foo" +sayit(25); #=> "Number: 25" +sayit(True); # fails at *compile time* with "calling 'sayit' will never + # work with arguments of types ..." -## with arbitrary precondition (remember subsets?): -multi is-big(Int $n where * > 50) { "Yes !" } # using a closure -multi is-big(Int $ where 10..50) { "Quite." } # Using smart-matching - # (could use a regexp, etc) +## with arbitrary preconditions (remember subsets?): +multi is-big(Int $n where * > 50) { "Yes!" } # using a closure +multi is-big(Int $n where {$_ > 50}) { "Yes!" } # similar to above +multi is-big(Int $ where 10..50) { "Quite." } # Using smart-matching + # (could use a regexp, etc) multi is-big(Int $) { "No" } subset Even of Int where * %% 2; - multi odd-or-even(Even) { "Even" } # The main case using the type. # We don't name the argument. -multi odd-or-even($) { "Odd" } # "else" +multi odd-or-even($) { "Odd" } # "everthing else" hence the $ variable -## You can even dispatch based on a positional's argument presence ! -multi with-or-without-you(:$with!) { # You need make it mandatory to - # be able to dispatch against it. - say "I can live ! Actually, I can't."; +## You can even dispatch based on the presence of positional and +## named arguments: +multi with-or-without-you($with) { + say "I wish I could but I can't"; +} +multi with-or-without-you(:$with) { + say "I can live! Actually, I can't."; } multi with-or-without-you { - say "Definitely can't live."; + say "Definitely can't live."; } -## This is very, very useful for many purposes, like `MAIN` subs (covered -## later), and even the language itself is using it in several places. + +## This is very, very useful for many purposes, like `MAIN` subs (covered +## later), and even the language itself uses it in several places. ## ## - `is`, for example, is actually a `multi sub` named `trait_mod:`, ## and it works off that. ## - `is rw`, is simply a dispatch to a function with this signature: ## sub trait_mod:(Routine $r, :$rw!) {} ## -## (commented because running this would be a terrible idea !) +## (commented out because running this would be a terrible idea!) ``` ## Scoping @@ -705,175 +801,207 @@ multi with-or-without-you { ## In Perl 6, unlike many scripting languages, (such as Python, Ruby, PHP), ## you must declare your variables before using them. The `my` declarator ## you have learned uses "lexical scoping". There are a few other declarators, -## (`our`, `state`, ..., ) which we'll see later. -## This is called "lexical scoping", where in inner blocks, -## you can access variables from outer blocks. +## (`our`, `state`, ..., ) which we'll see later. This is called +## "lexical scoping", where in inner blocks, you can access variables from +## outer blocks. my $file_scoped = 'Foo'; sub outer { - my $outer_scoped = 'Bar'; - sub inner { - say "$file_scoped $outer_scoped"; - } - &inner; # return the function + my $outer_scoped = 'Bar'; + sub inner { + say "$file_scoped $outer_scoped"; + } + &inner; # return the function } -outer()(); #=> 'Foo Bar' +outer()(); #=> 'Foo Bar' ## As you can see, `$file_scoped` and `$outer_scoped` were captured. -## But if we were to try and use `$bar` outside of `foo`, +## But if we were to try and use `$outer_scoped` outside the `outer` sub, ## the variable would be undefined (and you'd get a compile time error). ``` ## Twigils ```perl6 -## There are many special `twigils` (composed sigil's) in Perl 6. -## Twigils define the variables' scope. +## There are many special `twigils` (composed sigils) in Perl 6. Twigils +## define the variables' scope. ## The * and ? twigils work on standard variables: ## * Dynamic variable ## ? Compile-time variable ## The ! and the . twigils are used with Perl 6's objects: -## ! Attribute (class member) +## ! Attribute (instance attribute) ## . Method (not really a variable) -## `*` Twigil: Dynamic Scope -## These variables use the`*` twigil to mark dynamically-scoped variables. +## `*` twigil: Dynamic Scope +## These variables use the `*` twigil to mark dynamically-scoped variables. ## Dynamically-scoped variables are looked up through the caller, not through -## the outer scope +## the outer scope. my $*dyn_scoped_1 = 1; my $*dyn_scoped_2 = 10; sub say_dyn { - say "$*dyn_scoped_1 $*dyn_scoped_2"; + say "$*dyn_scoped_1 $*dyn_scoped_2"; } sub call_say_dyn { my $*dyn_scoped_1 = 25; # Defines $*dyn_scoped_1 only for this sub. - $*dyn_scoped_2 = 100; # Will change the value of the file scoped variable. - say_dyn(); #=> 25 100 $*dyn_scoped 1 and 2 will be looked for in the call. - # It uses the value of $*dyn_scoped_1 from inside this sub's - # lexical scope even though the blocks aren't nested (they're - # call-nested). -} -say_dyn(); #=> 1 10 + $*dyn_scoped_2 = 100; # Will change the value of the file scoped variable. + say_dyn(); #=> 25 100, $*dyn_scoped 1 and 2 will be looked + # for in the call. + # It uses the value of $*dyn_scoped_1 from inside + # this sub's lexical scope even though the blocks + # aren't nested (they're call-nested). +} +say_dyn(); #=> 1 10 call_say_dyn(); #=> 25 100 # Uses $*dyn_scoped_1 as defined in call_say_dyn even though # we are calling it from outside. -say_dyn(); #=> 1 100 We changed the value of $*dyn_scoped_2 in call_say_dyn - # so now its value has changed. +say_dyn(); #=> 1 100 We changed the value of $*dyn_scoped_2 in + # call_say_dyn so now its value has changed. ``` ## Object Model ```perl6 ## To call a method on an object, add a dot followed by the method name: -## => $object.method +## `$object.method` + ## Classes are declared with the `class` keyword. Attributes are declared -## with the `has` keyword, and methods declared with `method`. -## Every attribute that is private uses the ! twigil for example: `$!attr`. -## Immutable public attributes use the `.` twigil. -## (you can make them mutable with `is rw`) -## The easiest way to remember the `$.` twigil is comparing it to how methods -## are called. - -## Perl 6's object model ("SixModel") is very flexible, -## and allows you to dynamically add methods, change semantics, etc ... -## (these will not all be covered here, and you should refer to: +## with the `has` keyword, and methods declared with the `method` keyword. + +## Every attribute that is private uses the ! twigil. For example: `$!attr`. +## Immutable public attributes use the `.` twigil which creates a read-only +## method named after the attribute. In fact, declaring an attribute with `.` +## is equivalent to declaring the same attribute with `!` and then creating +## a read-only method with the attribute's name. However, this is done for us +## by Perl 6 automatically. The easiest way to remember the `$.` twigil is +## by comparing it to how methods are called. + +## Perl 6's object model ("SixModel") is very flexible, and allows you to +## dynamically add methods, change semantics, etc... Unfortunately, these will +## not all be covered here, and you should refer to: ## https://docs.perl6.org/language/objects.html. -class Attrib-Class { - has $.attrib; # `$.attrib` is immutable. - # From inside the class, use `$!attrib` to modify it. - has $.other-attrib is rw; # You can mark a public attribute `rw`. - has Int $!private-attrib = 10; - - method get-value { - $.attrib + $!private-attrib; - } +class Human { + has Str $.name; # `$.name` is immutable but with an accessor method. + has Str $.bcountry; # Use `$!bplace` to modify it inside the class. + has Str $.ccountry is rw; # This attribute can be modified from outside. + has Int $!age = 0; # A private attribute with default value. - method set-value($param) { # Methods can take parameters - $!attrib = $param; # This works, because `$!` is always mutable. - # $.attrib = $param; # Wrong: You can't use the `$.` immutable version. + method birthday { + $!age += 1; # Add a year to human's age + } - $.other-attrib = 5; # This works, because `$.other-attrib` is `rw`. - } + method get-age { + return $!age; + } - method !private-method { - say "This method is private to the class !"; - } + # This method is private to the class. Note the `!` before the + # method's name. + method !do-decoration { + return "$!name was born in $!bcountry and now lives in $!ccountry." + } + + # This method is public, just like `birthday` and `get-age`. + method get-info { + self.do-decoration; # Invoking a method on `self` inside the class. + # Use `self!priv-method` for private method. + # Use `self.publ-method` for public method. + } }; -## Create a new instance of Attrib-Class with $.attrib set to 5 : +## Create a new instance of Human class with $.attrib set to 5. ## Note: you can't set private-attribute from here (more later on). -my $class-obj = Attrib-Class.new(attrib => 5); -say $class-obj.get-value; #=> 15 -# $class-obj.attrib = 5; # This fails, because the `has $.attrib` is immutable -$class-obj.other-attrib = 10; # This, however, works, because the public - # attribute is mutable (`rw`). +my $person1 = Human.new( + name => "Jord", + bcountry = "Iceland", + ccountry => "Iceland" +); + +say $person1.name; #=> Jord +say $person1.bcountry; #=> Togo +say $person1.ccountry; #=> Togo + + +# $person1.bcountry = "Mali"; # This fails, because the `has $.bcountry` + # is immutable. Jord can't change his birthplace. +$person1.ccountry = "France"; # This works because the `$.ccountry` is mutable + # (`is rw`). Now Jord's current country is France. + +# Calling methods on the instance objects. +$person1.birthday; #=> 1 +$person1.get-info; #=> Jord was born in Togo and now lives in France. +$person1.do-decoration; # This fails since the method `do-decoration` is + # private. ``` ### Object Inheritance ```perl6 -## Perl 6 also has inheritance (along with multiple inheritance) -## While `method`'s are inherited, `submethod`'s are not. -## Submethods are useful for object construction and destruction tasks, -## such as BUILD, or methods that must be overridden by subtypes. -## We will learn about BUILD later on. +## Perl 6 also has inheritance (along with multiple inheritance). While +## methods are inherited, submethods are not. Submethods are useful for +## object construction and destruction tasks, such as BUILD, or methods that +## must be overridden by subtypes. We will learn about BUILD later on. class Parent { - has $.age; - has $.name; - # This submethod won't be inherited by Child. - submethod favorite-color { - say "My favorite color is Blue"; - } - # This method is inherited - method talk { say "Hi, my name is $!name" } + has $.age; + has $.name; + + # This submethod won't be inherited by the Child class. + submethod favorite-color { + say "My favorite color is Blue"; + } + + # This method is inherited + method talk { say "Hi, my name is $!name" } } + # Inheritance uses the `is` keyword class Child is Parent { - method talk { say "Goo goo ga ga" } - # This shadows Parent's `talk` method, This child hasn't learned to speak yet! + method talk { say "Goo goo ga ga" } + # This shadows Parent's `talk` method. + # This child hasn't learned to speak yet! } + my Parent $Richard .= new(age => 40, name => 'Richard'); -$Richard.favorite-color; #=> "My favorite color is Blue" -$Richard.talk; #=> "Hi, my name is Richard" -## $Richard is able to access the submethod, he knows how to say his name. +$Richard.favorite-color; #=> "My favorite color is Blue" +$Richard.talk; #=> "Hi, my name is Richard" +## $Richard is able to access the submethod and he knows how to say his name. my Child $Madison .= new(age => 1, name => 'Madison'); -$Madison.talk; # prints "Goo goo ga ga" due to the overridden method. -# $Madison.favorite-color # does not work since it is not inherited +$Madison.talk; #=> "Goo goo ga ga", due to the overridden method. +# $Madison.favorite-color # does not work since it is not inherited. ## When you use `my T $var`, `$var` starts off with `T` itself in it, ## so you can call `new` on it. ## (`.=` is just the dot-call and the assignment operator: -## `$a .= b` is the same as `$a = $a.b`) +## `$a .= b` is the same as `$a = $a.b`) ## Also note that `BUILD` (the method called inside `new`) -## will set parent properties too, so you can pass `val => 5`. +## will set parent's properties too, so you can pass `val => 5`. ``` ### Roles, or Mixins ```perl6 -## Roles are supported too (also called Mixins in other languages) +## Roles are supported too (which are called Mixins in other languages) role PrintableVal { - has $!counter = 0; - method print { - say $.val; - } + has $!counter = 0; + method print { + say $.val; + } } -## you "import" a mixin (a "role") with "does": +## you "apply" a role (or mixin) with `does` keyword: class Item does PrintableVal { - has $.val; + has $.val; - ## When `does`-ed, a `role` literally "mixes in" the class: - ## the methods and attributes are put together, which means a class can access - ## the private attributes/methods of its roles (but not the inverse !): - method access { - say $!counter++; - } + ## When `does`-ed, a `role` literally "mixes in" the class: + ## the methods and attributes are put together, which means a class + ## can access the private attributes/methods of its roles (but + ## not the inverse!): + method access { + say $!counter++; + } ## However, this: ## method print {} @@ -881,9 +1009,9 @@ class Item does PrintableVal { ## (this means a parent class can shadow a child class's `multi print() {}`, ## but it's an error if a role does) - ## NOTE: You can use a role as a class (with `is ROLE`). In this case, - ## methods will be shadowed, since the compiler will consider `ROLE` to - ## be a class. + ## NOTE: You can use a role as a class (with `is ROLE`). In this case, + ## methods will be shadowed, since the compiler will consider `ROLE` + ## to be a class. } ``` @@ -891,91 +1019,109 @@ class Item does PrintableVal { ```perl6 ## Exceptions are built on top of classes, in the package `X` (like `X::IO`). -## In Perl6 exceptions are automatically 'thrown' -open 'foo'; #> Failed to open file foo: no such file or directory -## It will also print out what line the error was thrown at and other error info +## In Perl6 exceptions are automatically 'thrown': +open 'foo'; #=> Failed to open file foo: no such file or directory +## It will also print out what line the error was thrown at +## and other error info. ## You can throw an exception using `die`: die 'Error!'; #=> Error! ## Or more explicitly: -die X::AdHoc.new(payload => 'Error!'); +X::AdHoc.new(payload => 'Error!').throw; #=> Error! ## In Perl 6, `orelse` is similar to the `or` operator, except it only matches -## undefined variables instead of anything evaluating as false. +## undefined variables instead of anything evaluating as `False`. ## Undefined values include: `Nil`, `Mu` and `Failure` as well as `Int`, `Str` ## and other types that have not been initialized to any value yet. ## You can check if something is defined or not using the defined method: my $uninitialized; -say $uninitiazilzed.defined; #> False -## When using `orelse` it will disarm the exception and alias $_ to that failure -## This will avoid it being automatically handled and printing lots of scary -## error messages to the screen. -## We can use the exception method on $_ to access the exception +say $uninitiazilzed.defined; #=> False + +## When using `orelse` it will disarm the exception and alias $_ to that +## failure. This will prevent it to being automatically handled and printing +## lots of scary error messages to the screen. We can use the `exception` +## method on the `$_` variable to access the exception open 'foo' orelse say "Something happened {.exception}"; ## This also works: -open 'foo' orelse say "Something happened $_"; #> Something happened - #> Failed to open file foo: no such file or directory -## Both of those above work but in case we get an object from the left side that -## is not a failure we will probably get a warning. We see below how we can use -## `try` and `CATCH` to be more specific with the exceptions we catch. +open 'foo' orelse say "Something happened $_"; #=> Something happened + #=> Failed to open file foo: no such file or directory +## Both of those above work but in case we get an object from the left side +## that is not a failure we will probably get a warning. We see below how we +## can use try` and `CATCH` to be more specific with the exceptions we catch. ``` ### Using `try` and `CATCH` ```perl6 ## By using `try` and `CATCH` you can contain and handle exceptions without -## disrupting the rest of the program. `try` will set the last exception to -## the special variable `$!` Note: This has no relation to $!variables. +## disrupting the rest of the program. The `try` block will set the last +## exception to the special variable `$!` (known as the error variable). +## Note: This has no relation to $!variables seen inside class definitions. + try open 'foo'; -say "Well, I tried! $!" if defined $!; #> Well, I tried! Failed to open file - #foo: no such file or directory +say "Well, I tried! $!" if defined $!; +#=> Well, I tried! Failed to open file foo: no such file or directory + ## Now, what if we want more control over handling the exception? ## Unlike many other languages, in Perl 6, you put the `CATCH` block *within* -## the block to `try`. Similar to how $_ was set when we 'disarmed' the -## exception with orelse, we also use $_ in the CATCH block. -## Note: ($! is only set *after* the `try` block) -## By default, a `try` has a `CATCH` block that catches -## any exception (`CATCH { default {} }`). +## the block to `try`. Similar to how the `$_` variable was set when we +## 'disarmed' the exception with `orelse`, we also use `$_` in the CATCH block. +## Note: The `$!` variable is only set *after* the `try` block has caught an +## exception. By default, a `try` block has a `CATCH` block of its own that +## catches any exception (`CATCH { default {} }`). -try { my $a = (0 %% 0); CATCH { say "Something happened: $_" } } - #=> Something happened: Attempt to divide by zero using infix:<%%> +try { + my $a = (0 %% 0); + CATCH { + say "Something happened: $_" + } +} +#=> Something happened: Attempt to divide by zero using infix:<%%> + +## You can redefine it using `when`s (and `default`) to handle the exceptions +## you want to catch explicitly: -## You can redefine it using `when`s (and `default`) -## to handle the exceptions you want: try { open 'foo'; - CATCH { # In the `CATCH` block, the exception is set to $_ - when X::AdHoc { say "Error: $_" } - #=>Error: Failed to open file /dir/foo: no such file or directory - - ## Any other exception will be re-raised, since we don't have a `default` - ## Basically, if a `when` matches (or there's a `default`) marks the - ## exception as - ## "handled" so that it doesn't get re-thrown from the `CATCH`. - ## You still can re-throw the exception (see below) by hand. + CATCH { + # In the `CATCH` block, the exception is set to the $_ variable. + when X::AdHoc { + say "Error: $_" + } + when X::Numeric::DivideByZero { + say "Error: $_"; + } + ## Any other exceptions will be re-raised, since we don't have a `default`. + ## Basically, if a `when` matches (or there's a `default`), the + ## exception is marked as "handled" so as to prevent its re-throw + ## from the `CATCH` block. You still can re-throw the exception (see below) + ## by hand. } } +#=>Error: Failed to open file /dir/foo: no such file or directory ## There are also some subtleties to exceptions. Some Perl 6 subs return a -## `Failure`, which is a kind of "unthrown exception". They're not thrown until -## you tried to look at their content, unless you call `.Bool`/`.defined` on -## them - then they're handled. +## `Failure`, which is a wrapper around an `Exception` object which is +## "unthrown". They're not thrown until you try to use the variables containing +## them unless you call `.Bool`/`.defined` on them - then they're handled. ## (the `.handled` method is `rw`, so you can mark it as `False` back yourself) -## ## You can throw a `Failure` using `fail`. Note that if the pragma `use fatal` ## is on, `fail` will throw an exception (like `die`). + fail "foo"; # We're not trying to access the value, so no problem. try { - fail "foo"; - CATCH { - default { say "It threw because we tried to get the fail's value!" } + fail "foo"; + CATCH { + default { + say "It threw because we tried to get the fail's value!" + } } } ## There is also another kind of exception: Control exceptions. -## Those are "good" exceptions, which happen when you change your program's +## Those are "good" exceptions, which happen when you change your program's ## flow, using operators like `return`, `next` or `last`. ## You can "catch" those with `CONTROL` (not 100% working in Rakudo yet). ``` @@ -989,29 +1135,35 @@ try { ## Packages are important - especially as Perl is well-known for CPAN, ## the Comprehensive Perl Archive Network. -## You can use a module (bring its declarations into scope) with `use` +## You can use a module (bring its declarations into scope) with +## the `use` keyword: use JSON::Tiny; # if you installed Rakudo* or Panda, you'll have this module say from-json('[1]').perl; #=> [1] ## You should not declare packages using the `package` keyword (unlike Perl 5). ## Instead, use `class Package::Name::Here;` to declare a class, or if you only -## want to export variables/subs, you can use `module`. +## want to export variables/subs, you can use `module` instead. + +module Hello::World { # bracketed form + # If `Hello` doesn't exist yet, it'll just be a "stub", + # that can be redeclared as something else later. -module Hello::World { # Bracketed form - # If `Hello` doesn't exist yet, it'll just be a "stub", - # that can be redeclared as something else later. - # ... declarations here ... + # ... declarations here ... } -unit module Parse::Text; # file-scoped form -grammar Parse::Text::Grammar { # A grammar is a package, which you could `use` -} # You will learn more about grammars in the regex section +unit module Parse::Text; # file-scoped form which extends until + # the end of the file + +grammar Parse::Text::Grammar { + # A grammar is a package, which you could `use`. + # You will learn more about grammars in the regex section +} ## As said before, any part of the six model is also a package. ## Since `JSON::Tiny` uses its own `JSON::Tiny::Actions` class, you can use it: my $actions = JSON::Tiny::Actions.new; -## We'll see how to export variables and subs in the next part: +## We'll see how to export variables and subs in the next part. ``` ## Declarators @@ -1020,36 +1172,38 @@ my $actions = JSON::Tiny::Actions.new; ## In Perl 6, you get different behaviors based on how you declare a variable. ## You've already seen `my` and `has`, we'll now explore the others. -## * `our` declarations happen at `INIT` time -- (see "Phasers" below) -## It's like `my`, but it also creates a package variable. -## (All packagish things (`class`, `role`, etc) are `our` by default) -module Var::Increment { - our $our-var = 1; # Note: you can't put a type constraint like Int on an - my $my-var = 22; # `our` variable. - our sub Inc { - - our sub available { # If you try to make inner `sub`s `our`... - # Better know what you're doing (Don't !). - say "Don't do that. Seriously. You'll get burned."; - } +## `our` - these declarations happen at `INIT` time -- (see "Phasers" below). +## It's like `my`, but it also creates a package variable. All packagish +## things such as `class`, `role`, etc. are `our` by default. - my sub unavailable { # `my sub` is the default - say "Can't access me from outside, I'm 'my'!"; - } - say ++$our-var; # Increment the package variable and output its value +module Var::Increment { + our $our-var = 1; # Note: `our`-declared variables cannot be typed. + my $my-var = 22; + + our sub Inc { + our sub available { # If you try to make inner `sub`s `our`... + # ... Better know what you're doing (Don't !). + say "Don't do that. Seriously. You'll get burned."; + } + + my sub unavailable { # `sub`s are `my`-declared by default + say "Can't access me from outside, I'm 'my'!"; + } + say ++$our-var; # Increment the package variable and output its value } } -say $Var::Increment::our-var; #=> 1 This works -say $Var::Increment::my-var; #=> (Any) This will not work. -Var::Increment::Inc; #=> 2 -Var::Increment::Inc; #=> 3 # Notice how the value of $our-var was - # retained. -Var::Increment::unavailable; #> Could not find symbol '&unavailable' +say $Var::Increment::our-var; #=> 1, this works! +say $Var::Increment::my-var; #=> (Any), this will not work! + +Var::Increment::Inc; #=> 2 +Var::Increment::Inc; #=> 3 , notice how the value of $our-var was + # retained. +Var::Increment::unavailable; #=> Could not find symbol '&unavailable' -## * `constant` (happens at `BEGIN` time) -## You can use the `constant` keyword to declare a compile-time variable/symbol: +## `constant` - these declarations happen at `BEGIN` time. You can use +## the `constant` keyword to declare a compile-time variable/symbol: constant Pi = 3.14; constant $var = 1; @@ -1057,12 +1211,12 @@ constant $var = 1; constant why-not = 5, 15 ... *; say why-not[^5]; #=> 5 15 25 35 45 -## * `state` (happens at run time, but only once) -## State variables are only initialized one time -## (they exist in other languages such as C as `static`) +## `state` - these declarations happen at run time, but only once. State +## variables are only initialized one time. In other languages such as C +## they exist as `static` variables. sub fixed-rand { - state $val = rand; - say $val; + state $val = rand; + say $val; } fixed-rand for ^10; # will print the same number 10 times @@ -1070,40 +1224,42 @@ fixed-rand for ^10; # will print the same number 10 times ## If you declare a function with a `state` within a loop, it'll re-create the ## variable for each iteration of the loop. See: for ^5 -> $a { - sub foo { - state $val = rand; # This will be a different value for every value of `$a` - } - for ^5 -> $b { - say foo; # This will print the same value 5 times, but only 5. - # Next iteration will re-run `rand`. - } + sub foo { + state $val = rand; # This will be a different value for + # every value of `$a` + } + for ^5 -> $b { + say foo; # This will print the same value 5 times, + # but only 5. Next iteration will re-run `rand`. + } } ``` ## Phasers ```perl6 -## Phasers in Perl 6 are blocks that happen at determined points of time in your -## program. They are called phasers because they mark a change in the phase -## of a program. For example, when the program is compiled, a for loop runs, -## you leave a block, or an exception gets thrown. -## (`CATCH` is actually a phaser!) -## Some of them can be used for their return values, some of them can't -## (those that can have a "[*]" in the beginning of their explanation text). -## Let's have a look ! - -## * Compile-time phasers +## Phasers in Perl 6 are blocks that happen at determined points of time in +## your program. They are called phasers because they mark a change in the +## phase of a program. For example, when the program is compiled, a for loop +## runs, you leave a block, or an exception gets thrown (The `CATCH` block is +## actually a phaser!). Some of them can be used for their return values, +## some of them can't (those that can have a "[*]" in the beginning of their +## explanation text). Let's have a look! + +## Compile-time phasers BEGIN { say "[*] Runs at compile time, as soon as possible, only once" } CHECK { say "[*] Runs at compile time, as late as possible, only once" } -## * Run-time phasers +## Run-time phasers INIT { say "[*] Runs at run time, as soon as possible, only once" } -END { say "Runs at run time, as late as possible, only once" } +END { say "Runs at run time, as late as possible, only once" } -## * Block phasers +## Block phasers ENTER { say "[*] Runs everytime you enter a block, repeats on loop blocks" } -LEAVE { say "Runs everytime you leave a block, even when an exception - happened. Repeats on loop blocks." } +LEAVE { + say "Runs everytime you leave a block, even when an exception + happened. Repeats on loop blocks." +} PRE { say "Asserts a precondition at every block entry, @@ -1112,7 +1268,7 @@ PRE { an exception of type X::Phaser::PrePost is thrown."; } -## example: +## Example: for 0..2 { PRE { $_ > 1 } # This is going to blow up with "Precondition failed" } @@ -1123,83 +1279,86 @@ POST { say "If this block doesn't return a truthy value, an exception of type X::Phaser::PrePost is thrown, like PRE."; } + for 0..2 { POST { $_ < 2 } # This is going to blow up with "Postcondition failed" } -## * Block/exceptions phasers +## Block/exceptions phasers sub { KEEP { say "Runs when you exit a block successfully (without throwing an exception)" } - UNDO { say "Runs when you exit a block unsuccessfully + UNDO { say "Runs when you exit a block unsuccessfully (by throwing an exception)" } } -## * Loop phasers +## Loop phasers for ^5 { FIRST { say "[*] The first time the loop is run, before ENTER" } - NEXT { say "At loop continuation time, before LEAVE" } - LAST { say "At loop termination time, after LEAVE" } + NEXT { say "At loop continuation time, before LEAVE" } + LAST { say "At loop termination time, after LEAVE" } } -## * Role/class phasers +## Role/class phasers COMPOSE { "When a role is composed into a class. /!\ NOT YET IMPLEMENTED" } -## They allow for cute tricks or clever code ...: +## They allow for cute tricks or clever code...: say "This code took " ~ (time - CHECK time) ~ "s to compile"; ## ... or clever organization: sub do-db-stuff { - $db.start-transaction; # start a new transaction - KEEP $db.commit; # commit the transaction if all went well - UNDO $db.rollback; # or rollback if all hell broke loose + $db.start-transaction; # start a new transaction + KEEP $db.commit; # commit the transaction if all went well + UNDO $db.rollback; # or rollback if all hell broke loose } ``` ## Statement prefixes ```perl6 -## Those act a bit like phasers: they affect the behavior of the following code. -## Though, they run in-line with the executable code, so they're in lowercase. -## (`try` and `start` are theoretically in that list, but explained elsewhere) -## Note: all of these (except start) don't need explicit brackets `{` and `}`. +## Those act a bit like phasers: they affect the behavior of the following +## code. Though, they run in-line with the executable code, so they're in +## lowercase. (`try` and `start` are theoretically in that list, but explained +## elsewhere) Note: all of these (except start) don't need explicit curly +## braces `{` and `}`. -## - `do` (that you already saw) - runs a block or a statement as a term -## You can't normally use a statement as a value (or "term"): -## -## my $value = if True { 1 } # `if` is a statement - parse error -## -## This works: -my $a = do if True { 5 } # with `do`, `if` is now a term. - -## - `once` - Makes sure a piece of code only runs once -for ^5 { once say 1 }; #=> 1 - # Only prints ... once. -## Like `state`, they're cloned per-scope -for ^5 { sub { once say 1 }() } #=> 1 1 1 1 1 - # Prints once per lexical scope - -## - `gather` - Co-routine thread -## Gather allows you to `take` several values in an array, -## much like `do`, but allows you to take any expression. +## `do` - (which you already saw) runs a block or a statement as a term. +## Normally you cannot use a statement as a value (or "term"). `do` helps us +## do it. + +# my $value = if True { 1 } # this fails since `if` is a statement +my $a = do if True { 5 } # with `do`, `if` is now a term returning a value + +## `once` - makes sure a piece of code only runs once. +for ^5 { + once say 1 +}; #=> 1, only prints ... once + +## Similar to `state`, they're cloned per-scope. +for ^5 { + sub { once say 1 }() +}; #=> 1 1 1 1 1, prints once per lexical scope. + +## `gather` - co-routine thread. The `gather` constructs allows us to `take` +## several values from an array/list, much like `do`. say gather for ^5 { - take $_ * 3 - 1; - take $_ * 3 + 1; -} #=> -1 1 2 4 5 7 8 10 11 13 + take $_ * 3 - 1; + take $_ * 3 + 1; +} +#=> -1 1 2 4 5 7 8 10 11 13 + say join ',', gather if False { - take 1; - take 2; - take 3; -} # Doesn't print anything. + take 1; + take 2; + take 3; +} +# Doesn't print anything. -## - `eager` - Evaluate statement eagerly (forces eager context) +## `eager` - evaluates a statement eagerly (forces eager context) ## Don't try this at home: -## -## eager 1..*; # this will probably hang for a while (and might crash ...). -## +# eager 1..*; # this will probably hang for a while (and might crash ...). ## But consider: constant thrice = gather for ^3 { say take $_ }; # Doesn't print anything - ## versus: constant thrice = eager gather for ^3 { say take $_ }; #=> 0 1 2 ``` @@ -1207,102 +1366,105 @@ constant thrice = eager gather for ^3 { say take $_ }; #=> 0 1 2 ## Iterables ```perl6 -## Iterables are objects that can be iterated similar to the `for` construct -## `flat`, flattens iterables: -say (1, 10, (20, 10) ); #> (1 10 (20 10)) Notice how grouping is maintained -say (1, 10, (20, 10) ).flat; #> (1 10 20 10) Now the iterable is flat +## Iterables are objects that can be iterated over which are +## are similar to the `for` construct. -## - `lazy` - Defer actual evaluation until value is fetched -## (forces lazy context) +## `flat` - flattens iterables. +say (1, 10, (20, 10) ); #=> (1 10 (20 10)), notice how neste lists are + # preserved +say (1, 10, (20, 10) ).flat; #=> (1 10 20 10), now the iterable is flat + +## - `lazy` - defers actual evaluation until value is fetched by forcing +## lazy context. my @lazy-array = (1..100).lazy; -say @lazy-array.is-lazy; #> True # Check for laziness with the `is-lazy` method. -say @lazy-array; #> [...] List has not been iterated on! +say @lazy-array.is-lazy; #=> True, check for laziness with the `is-lazy` method. +say @lazy-array; #=> [...] List has not been iterated on! my @lazy-array { .print }; # This works and will only do as much work as # is needed. -[//]: # ( TODO explain that gather/take and map are all lazy) -## - `sink` - An `eager` that discards the results (forces sink context) + +# ( **TODO** explain that gather/take and map are all lazy) + +## `sink` - an `eager` that discards the results by forcing sink context. constant nilthingie = sink for ^3 { .say } #=> 0 1 2 -say nilthingie.perl; #=> Nil +say nilthingie.perl; #=> Nil -## - `quietly` blocks will suppress warnings: +## `quietly` - suppresses warnings in blocks. quietly { warn 'This is a warning!' }; #=> No output -## - `contend` - Attempts side effects under STM -## Not yet implemented ! +## `contend` - attempts side effects under STM +## Not yet implemented! ``` -## More operators thingies ! +## More operators thingies! ```perl6 -## Everybody loves operators ! Let's get more of them +## Everybody loves operators! Let's get more of them. ## The precedence list can be found here: ## https://docs.perl6.org/language/operators#Operator_Precedence ## But first, we need a little explanation about associativity: -## * Binary operators: +## Binary operators: $a ! $b ! $c; # with a left-associative `!`, this is `($a ! $b) ! $c` $a ! $b ! $c; # with a right-associative `!`, this is `$a ! ($b ! $c)` $a ! $b ! $c; # with a non-associative `!`, this is illegal $a ! $b ! $c; # with a chain-associative `!`, this is `($a ! $b) and ($b ! $c)` $a ! $b ! $c; # with a list-associative `!`, this is `infix:<>` -## * Unary operators: +## Unary operators: !$a! # with left-associative `!`, this is `(!$a)!` !$a! # with right-associative `!`, this is `!($a!)` !$a! # with non-associative `!`, this is illegal ``` -### Create your own operators ! +### Create your own operators! ```perl6 -## Okay, you've been reading all of that, so I guess I should try -## to show you something exciting. -## I'll tell you a little secret (or not-so-secret): +## Okay, you've been reading all of that, so you might want to try something +## more exciting?! I'll tell you a little secret (or not-so-secret): ## In Perl 6, all operators are actually just funny-looking subroutines. ## You can declare an operator just like you declare a sub: -sub prefix:($winner) { # refer to the operator categories - # (yes, it's the "words operator" `<>`) - say "$winner Won !"; +# prefix refers to the operator categories (prefix, infix, postfix, etc). +sub prefix:( $winner ) { + say "$winner Won!"; } -win "The King"; #=> The King Won ! - # (prefix is before) +win "The King"; #=> The King Won! + # (prefix means 'before') ## you can still call the sub with its "full name": -say prefix:(True); #=> False +say prefix:(True); #=> False +prefix:("The Queen"); #=> The Queen Won! -sub postfix:(Int $n) { - [*] 2..$n; # using the reduce meta-operator ... See below ;-) ! +sub postfix:( Int $n ) { + [*] 2..$n; # using the reduce meta-operator... See below ;-)! } say 5!; #=> 120 - # Postfix operators (after) have to come *directly* after the term. + # Postfix operators ('after') have to come *directly* after the term. # No whitespace. You can use parentheses to disambiguate, i.e. `(5!)!` - -sub infix:(Int $n, Block $r) { # infix in the middle - for ^$n { - $r(); # You need the explicit parentheses to call the function in `$r`, - # else you'd be referring at the variable itself, like with `&r`. - } +sub infix:( Int $n, Block $r ) { # infix ('between') + for ^$n { + $r(); # You need the explicit parentheses to call the function in `$r`, + # else you'd be referring at the variable itself, like with `&r`. + } } 3 times -> { say "hello" }; #=> hello #=> hello #=> hello - # You're very recommended to put spaces - # around your infix operator calls. +## It's recommended to put spaces around your +## infix operator calls. ## For circumfix and post-circumfix ones -sub circumfix:<[ ]>(Int $n) { - $n ** $n +sub circumfix:<[ ]>( Int $n ) { + $n ** $n } say [5]; #=> 3125 - # circumfix is around. Again, no whitespace. + # circumfix means 'around'. Again, no whitespace. -sub postcircumfix:<{ }>(Str $s, Int $idx) { - ## post-circumfix is - ## "after a term, around something" - $s.substr($idx, 1); +sub postcircumfix:<{ }>( Str $s, Int $idx ) { + ## post-circumfix is 'after a term, around something' + $s.substr($idx, 1); } say "abc"{1}; #=> b # after the term `"abc"`, and around the index (1) @@ -1312,47 +1474,47 @@ say "abc"{1}; #=> b ## (a simple named argument underneath): %h{$key}:delete; ## equivalent to: -postcircumfix:<{ }>(%h, $key, :delete); # (you can call operators like that) +postcircumfix:<{ }>( %h, $key, :delete ); # (you can call operators like this) -## It's *all* using the same building blocks! -## Syntactic categories (prefix infix ...), named arguments (adverbs), ..., -## - used to build the language - are available to you. -## (you are, obviously, recommended against making an operator out of -## *everything* -- with great power comes great responsibility) +## It's *all* using the same building blocks! Syntactic categories +## (prefix infix ...), named arguments (adverbs), ..., etc. used to build +## the language - are available to you. Obviously, you're advised against +## making an operator out of *everything* -- with great power comes great +## responsibility. ``` -### Meta operators ! +### Meta operators! ```perl6 -## Oh boy, get ready. Get ready, because we're delving deep -## into the rabbit's hole, and you probably won't want to go -## back to other languages after reading that. -## (I'm guessing you don't want to already at that point). +## Oh boy, get ready!. Get ready, because we're delving deep into the rabbit's +## hole, and you probably won't want to go back to other languages after +## reading this. (I'm guessing you don't want to go back at this point but +## let's continue, for the journey is long and enjoyable!). + ## Meta-operators, as their name suggests, are *composed* operators. -## Basically, they're operators that apply another operator. +## Basically, they're operators that act on another operators. + +## The reduce meta-operator is a prefix meta-operator that takes a binary +## function and one or many lists. If it doesn't get passed any argument, +## it either returns a "default value" for this operator (a meaningless value) +## or `Any` if there's none (examples below). Otherwise, it pops an element +## from the list(s) one at a time, and applies the binary function to the last +## result (or the list's first element) and the popped element. -## * Reduce meta-operator -## It's a prefix meta-operator that takes a binary function and -## one or many lists. If it doesn't get passed any argument, -## it either returns a "default value" for this operator -## (a meaningless value) or `Any` if there's none (examples below). -## -## Otherwise, it pops an element from the list(s) one at a time, and applies -## the binary function to the last result (or the list's first element) -## and the popped element. -## ## To sum a list, you could use the reduce meta-operator with `+`, i.e.: -say [+] 1, 2, 3; #=> 6 -## equivalent to `(1+2)+3` +say [+] 1, 2, 3; #=> 6, equivalent to (1+2)+3. -say [*] 1..5; #=> 120 -## equivalent to `((((1*2)*3)*4)*5)`. +## To multiply a list +say [*] 1..5; #=> 120, equivalent to ((((1*2)*3)*4)*5). ## You can reduce with any operator, not just with mathematical ones. -## For example, you could reduce with `//` to get -## the first defined element of a list: -say [//] Nil, Any, False, 1, 5; #=> False - # (Falsey, but still defined) +## For example, you could reduce with `//` to get first defined element +## of a list: +say [//] Nil, Any, False, 1, 5; #=> False + # (Falsey, but still defined) +## Or with relational operators, i.e., `>` to check elements of a list +## are ordered accordingly: +say say [>] 234, 156, 6, 3, -20; #=> True ## Default value examples: say [*] (); #=> 1 @@ -1365,15 +1527,14 @@ say [//]; #=> (Any) sub add($a, $b) { $a + $b } say [[&add]] 1, 2, 3; #=> 6 -## * Zip meta-operator -## This one is an infix meta-operator that also can be used as a "normal" -## operator. It takes an optional binary function (by default, it just creates -## a pair), and will pop one value off of each array and call its binary -## function on these until it runs out of elements. It returns an array with -## all of these new elements. -(1, 2) Z (3, 4); # ((1, 3), (2, 4)), since by default, the function - # makes an array. -1..3 Z+ 4..6; # (5, 7, 9), using the custom infix:<+> function +## The zip meta-operator is an infix meta-operator that also can be used as a +## "normal" operator. It takes an optional binary function (by default, it +## just creates a pair), and will pop one value off of each array and call +## its binary function on these until it runs out of elements. It returns an +## array with all of these new elements. +say (1, 2) Z (3, 4); #=> ((1, 3), (2, 4)), since by default the function + # makes an array. +say 1..3 Z+ 4..6; #=> (5, 7, 9), using the custom infix:<+> function ## Since `Z` is list-associative (see the list above), ## you can use it on more than one list @@ -1385,252 +1546,258 @@ say [[&add]] 1, 2, 3; #=> 6 ## And to end the operator list: -## * Sequence operator ## The sequence operator is one of Perl 6's most powerful features: ## it's composed of first, on the left, the list you want Perl 6 to deduce from ## (and might include a closure), and on the right, a value or the predicate -## that says when to stop (or Whatever for a lazy infinite list). -my @list = 1, 2, 3 ... 10; # basic deducing -#my @list = 1, 3, 6 ... 10; # this dies because Perl 6 can't figure out the end -my @list = 1, 2, 3 ...^ 10; # as with ranges, you can exclude the last element - # (the iteration when the predicate matches). -my @list = 1, 3, 9 ... * > 30; # you can use a predicate - # (with the Whatever Star, here). -my @list = 1, 3, 9 ... { $_ > 30 }; # (equivalent to the above) - -my @fib = 1, 1, *+* ... *; # lazy infinite list of fibonacci series, - # computed using a closure! +## that says when to stop (or a Whatever Star for a lazy infinite list). + +my @list = 1, 2, 3...10; # basic arithmetic sequence +# my @list = 1, 3, 6...10; # this dies because Perl 6 can't figure out the end +my @list = 1, 2, 3...^10; # as with ranges, you can exclude the last element + # (the iteration ends when the predicate matches). +my @list = 1, 3, 9...* > 30; # you can use a predicate (with the Whatever Star). +my @list = 1, 3, 9 ... { $_ > 30 }; # (equivalent to the above + # using a block here). + +my @fib = 1, 1, *+* ... *; # lazy infinite list of fibonacci sequence, + # computed using a closure! my @fib = 1, 1, -> $a, $b { $a + $b } ... *; # (equivalent to the above) -my @fib = 1, 1, { $^a + $^b } ... *; #(... also equivalent to the above) +my @fib = 1, 1, { $^a + $^b } ... *; # (also equivalent to the above) ## $a and $b will always take the previous values, meaning here -## they'll start with $a = 1 and $b = 1 (values we set by hand). -## then $a = 1 and $b = 2 (result from previous $a+$b), and so on. +## they'll start with $a = 1 and $b = 1 (values we set by hand), +## then $a = 1 and $b = 2 (result from previous $a+$b), and so on. say @fib[^10]; #=> 1 1 2 3 5 8 13 21 34 55 # (using a range as the index) -## Note : as for ranges, once reified, elements aren't re-calculated. +## Note: as for ranges, once reified, elements aren't re-calculated. ## That's why `@primes[^100]` will take a long time the first time you print -## it, then be instant. +## it, then will be instateneous. ``` ## Regular Expressions ```perl6 -## I'm sure a lot of you have been waiting for this one. -## Well, now that you know a good deal of Perl 6 already, we can get started. -## First off, you'll have to forget about "PCRE regexps" (perl-compatible -## regexps). +## I'm sure a lot of you have been waiting for this one. Well, now that you know +## a good deal of Perl 6 already, we can get started. First off, you'll have to +## forget about "PCRE regexps" (perl-compatible regexps). ## -## IMPORTANT: Don't skip them because you know PCRE. They're different. -## Some things are the same (like `?`, `+`, and `*`), -## but sometimes the semantics change (`|`). -## Make sure you read carefully, because you might trip over a new behavior. +## IMPORTANT: Don't skip them because you know PCRE. They're different. Some +## things are the same (like `?`, `+`, and `*`), but sometimes the semantics +## change (`|`). Make sure you read carefully, because you might trip over a +## new behavior. ## ## Perl 6 has many features related to RegExps. After all, Rakudo parses itself. -## We're first going to look at the syntax itself, -## then talk about grammars (PEG-like), differences between -## `token`, `regex` and `rule` declarators, and some more. -## Side note: you still have access to PCRE regexps using the `:P5` modifier. -## (we won't be discussing this in this tutorial, however) +## We're first going to look at the syntax itself, then talk about grammars +## (PEG-like), differences between `token`, `regex` and `rule` declarators, +## and some more. Side note: you still have access to PCRE regexps using the +## `:P5` modifier which we won't be discussing this in this tutorial, though. ## ## In essence, Perl 6 natively implements PEG ("Parsing Expression Grammars"). ## The pecking order for ambiguous parses is determined by a multi-level -## tie-breaking test: -## - Longest token matching. `foo\s+` beats `foo` (by 2 or more positions) -## - Longest literal prefix. `food\w*` beats `foo\w*` (by 1) +## tie-breaking test: +## - Longest token matching: `foo\s+` beats `foo` (by 2 or more positions) +## - Longest literal prefix: `food\w*` beats `foo\w*` (by 1) ## - Declaration from most-derived to less derived grammars -## (grammars are actually classes) +## (grammars are actually classes) ## - Earliest declaration wins -say so 'a' ~~ /a/; #=> True -say so 'a' ~~ / a /; #=> True # More readable with some spaces! +say so 'a' ~~ /a/; #=> True +say so 'a' ~~ / a /; #=> True, more readable with some spaces! ## In all our examples, we're going to use the smart-matching operator against -## a regexp. We're converting the result using `so`, but in fact, it's -## returning a `Match` object. They know how to respond to list indexing, -## hash indexing, and return the matched string. -## The results of the match are available as `$/` (implicitly lexically-scoped). -## You can also use the capture variables which start at 0: -## `$0`, `$1', `$2`... +## a regexp. We're converting the result using `so` to a Boolean value because, +## in fact, it's returning a `Match` object. They know how to respond to list +## indexing, hash indexing, and return the matched string. The results of the +## match are available in the `$/` variable (implicitly lexically-scoped). You +## can also use the capture variables which start at 0: `$0`, `$1', `$2`... ## -## You can also note that `~~` does not perform start/end checking -## (meaning the regexp can be matched with just one char of the string), -## we're going to explain later how you can do it. - -## In Perl 6, you can have any alphanumeric as a literal, -## everything else has to be escaped, using a backslash or quotes. -say so 'a|b' ~~ / a '|' b /; # `True`. Wouldn't mean the same if `|` wasn't - # escaped -say so 'a|b' ~~ / a \| b /; # `True`. Another way to escape it. - -## The whitespace in a regexp is actually not significant, -## unless you use the `:s` (`:sigspace`, significant space) adverb. -say so 'a b c' ~~ / a b c /; #> `False`. Space is not significant here -say so 'a b c' ~~ /:s a b c /; #> `True`. We added the modifier `:s` here. +## You can also note that `~~` does not perform start/end checking, meaning +## the regexp can be matched with just one character of the string. We'll +## explain later how you can do it. + +## In Perl 6, you can have any alphanumeric as a literal, everything else has +## to be escaped by using a backslash or quotes. +say so 'a|b' ~~ / a '|' b /; #=> `True`, it wouldn't mean the same thing if + # `|` wasn't escaped. +say so 'a|b' ~~ / a \| b /; #=> `True`, another way to escape it. + +## The whitespace in a regexp is actually not significant, unless you use the +## `:s` (`:sigspace`, significant space) adverb. +say so 'a b c' ~~ / a b c /; #=> `False`, space is not significant here! +say so 'a b c' ~~ /:s a b c /; #=> `True`, we added the modifier `:s` here. + ## If we use only one space between strings in a regex, Perl 6 will warn us: -say so 'a b c' ~~ / a b c /; #> 'False' #> Space is not significant here; -## please use quotes or :s (:sigspace) modifier (or, to suppress this warning, -## omit the space, or otherwise change the spacing) -## To fix this and make the spaces less ambiguous, either use at least two -## spaces between strings or use the `:s` adverb. +say so 'a b c' ~~ / a b c /; #=> `False`, with warning about space +say so 'a b c' ~~ / a b c /; #=> `False` + +## Please use quotes or :s (:sigspace) modifier (or, to suppress this warning, +## omit the space, or otherwise change the spacing). To fix this and make the +## spaces less ambiguous, either use at least two spaces between strings +## or use the `:s` adverb. -## As we saw before, we can embed the `:s` inside the slash delimiters, but we +## As we saw before, we can embed the `:s` inside the slash delimiters, but we ## can also put it outside of them if we specify `m` for 'match': -say so 'a b c' ~~ m:s/a b c/; #> `True` -## By using `m` to specify 'match', we can also use delimiters other -## than slashes: -say so 'abc' ~~ m{a b c}; #> `True` +say so 'a b c' ~~ m:s/a b c/; #=> `True` + +## By using `m` to specify 'match', we can also use delimiters other than +## slashes: +say so 'abc' ~~ m{a b c}; #=> `True` +say so 'abc' ~~ m[a b c]; #=> `True` +# m/.../ is equivalent to /.../ ## Use the :i adverb to specify case insensitivity: -say so 'ABC' ~~ m:i{a b c}; #> `True` +say so 'ABC' ~~ m:i{a b c}; #=> `True` -## It is, however, important as for how modifiers (that you're gonna see just -## below) are applied ... +## However, whitespace is important as for how modifiers are applied ( +## (which you'll see just below) ... ## Quantifying - `?`, `+`, `*` and `**`. -## - `?` - 0 or 1 -so 'ac' ~~ / a b c /; # `False` -so 'ac' ~~ / a b? c /; # `True`, the "b" matched 0 times. -so 'abc' ~~ / a b? c /; # `True`, the "b" matched 1 time. +## `?` - zero or one match +so 'ac' ~~ / a b c /; #=> `False` +so 'ac' ~~ / a b? c /; #=> `True`, the "b" matched 0 times. +so 'abc' ~~ / a b? c /; #=> `True`, the "b" matched 1 time. -## ... As you read just before, whitespace is important because it determines -## which part of the regexp is the target of the modifier: -so 'def' ~~ / a b c? /; # `False`. Only the `c` is optional -so 'def' ~~ / a b? c /; # `False`. Whitespace is not significant -so 'def' ~~ / 'abc'? /; # `True`. The whole "abc" group is optional. +## ...As you read before, whitespace is important because it determines which +## part of the regexp is the target of the modifier: +so 'def' ~~ / a b c? /; #=> `False`, only the `c` is optional +so 'def' ~~ / a b? c /; #=> `False`, whitespace is not significant +so 'def' ~~ / 'abc'? /; #=> `True`, the whole "abc" group is optional ## Here (and below) the quantifier applies only to the `b` -## - `+` - 1 or more -so 'ac' ~~ / a b+ c /; # `False`; `+` wants at least one matching -so 'abc' ~~ / a b+ c /; # `True`; one is enough -so 'abbbbc' ~~ / a b+ c /; # `True`, matched 4 "b"s - -## - `*` - 0 or more -so 'ac' ~~ / a b* c /; # `True`, they're all optional. -so 'abc' ~~ / a b* c /; # `True` -so 'abbbbc' ~~ / a b* c /; # `True` -so 'aec' ~~ / a b* c /; # `False`. "b"(s) are optional, not replaceable. - -## - `**` - (Unbound) Quantifier -## If you squint hard enough, you might understand -## why exponentation is used for quantity. -so 'abc' ~~ / a b**1 c /; # `True` (exactly one time) -so 'abc' ~~ / a b**1..3 c /; # `True` (one to three times) -so 'abbbc' ~~ / a b**1..3 c /; # `True` -so 'abbbbbbc' ~~ / a b**1..3 c /; # `False` (too much) -so 'abbbbbbc' ~~ / a b**3..* c /; # `True` (infinite ranges are okay) - -## - `<[]>` - Character classes -## Character classes are the equivalent of PCRE's `[]` classes, but -## they use a more perl6-ish syntax: -say 'fooa' ~~ / f <[ o a ]>+ /; #=> 'fooa' +## `+` - one or more matches +so 'ac' ~~ / a b+ c /; #=> `False`, `+` wants at least one matching +so 'abc' ~~ / a b+ c /; #=> `True`, one is enough +so 'abbbbc' ~~ / a b+ c /; #=> `True`, matched 4 "b"s + +## `*` - zero or more matches +so 'ac' ~~ / a b* c /; #=> `True`, they're all optional. +so 'abc' ~~ / a b* c /; #=> `True` +so 'abbbbc' ~~ / a b* c /; #=> `True` +so 'aec' ~~ / a b* c /; #=> `False`. "b"(s) are optional, not replaceable. + +## `**` - (Unbound) Quantifier +## If you squint hard enough, you might understand why exponentation is used +## for quantity. +so 'abc' ~~ / a b**1 c /; #=> `True`, (exactly one time) +so 'abc' ~~ / a b**1..3 c /; #=> `True`, (one to three times) +so 'abbbc' ~~ / a b**1..3 c /; #=> `True` +so 'abbbbbbc' ~~ / a b**1..3 c /; #=> `False, (too much) +so 'abbbbbbc' ~~ / a b**3..* c /; #=> `True`, (infinite ranges are okay) + +## `<[]>` - Character classes +## Character classes are the equivalent of PCRE's `[]` classes, but they use a +## more perl6-ish syntax: +say 'fooa' ~~ / f <[ o a ]>+ /; #=> 'fooa' ## You can use ranges: say 'aeiou' ~~ / a <[ e..w ]> /; #=> 'ae' -## Just like in normal regexes, if you want to use a special character, -## escape it (the last one is escaping a space) +## Just like in normal regexes, if you want to use a special character, escape +## it (the last one is escaping a space which would be equivalent to using +## ' '): say 'he-he !' ~~ / 'he-' <[ a..z \! \ ]> + /; #=> 'he-he !' -## You'll get a warning if you put duplicate names -## (which has the nice effect of catching the wrote quoting:) -'he he' ~~ / <[ h e ' ' ]> /; # Warns "Repeated characters found in characters - # class" +## You'll get a warning if you put duplicate names (which has the nice effect +## of catching the raw quoting): +'he he' ~~ / <[ h e ' ' ]> /; +# Warns "Repeated character (') unexpectedly found in character class" -## You can also negate them ... (equivalent to `[^]` in PCRE) -so 'foo' ~~ / <-[ f o ]> + /; # False +## You can also negate character classes... (`<-[]>` equivalent to `[^]` in PCRE) +so 'foo' ~~ / <-[ f o ]> + /; #=> False -## ... and compose them: : -so 'foo' ~~ / <[ a..z ] - [ f o ]> + /; # False (any letter except f and o) -so 'foo' ~~ / <-[ a..z ] + [ f o ]> + /; # True (no letter except f and o) -so 'foo!' ~~ / <-[ a..z ] + [ f o ]> + /; # True (the + doesn't replace the +## ... and compose them: +so 'foo' ~~ / <[ a..z ] - [ f o ]> + /; #=> `False`, (any letter except f and o) +so 'foo' ~~ / <-[ a..z ] + [ f o ]> + /; #=> `True`, (no letter except f and o) +so 'foo!' ~~ / <-[ a..z ] + [ f o ]> + /; #=> `True`, (the + doesn't replace the # left part) ``` ### Grouping and capturing ```perl6 -## Group: you can group parts of your regexp with `[]`. -## These groups are *not* captured (like PCRE's `(?:)`). -so 'abc' ~~ / a [ b ] c /; # `True`. The grouping does pretty much nothing +## Group: you can group parts of your regexp with `[]`. Unlike PCRE's `(?:)`, +## these groups are *not* captured. +so 'abc' ~~ / a [ b ] c /; # `True`. The grouping does pretty much nothing so 'foo012012bar' ~~ / foo [ '01' <[0..9]> ] + bar /; -## The previous line returns `True`. -## We match the "012" 1 or more time (the `+` was applied to the group). + +## The previous line returns `True`. The regex matches "012" 1 or more time +## (achieved by the the `+` applied to the group). ## But this does not go far enough, because we can't actually get back what ## we matched. -## Capture: We can actually *capture* the results of the regexp, -## using parentheses. + +## Capture: The results of a regexp can be *captured* by using parentheses. so 'fooABCABCbar' ~~ / foo ( 'A' <[A..Z]> 'C' ) + bar /; # `True`. (using `so` # here, `$/` below) ## So, starting with the grouping explanations. -## As we said before, our `Match` object is available as `$/`: -say $/; # Will print some weird stuff (we'll explain) (or "Nil" if - # nothing matched). +## As we said before, our `Match` object is stored inside the `$/` variable: +say $/; # Will either print some weird stuff or `Nil` if nothing matched. ## As we also said before, it has array indexing: say $/[0]; #=> ｢ABC｣ ｢ABC｣ - # These weird brackets are `Match` objects. + # These corner brackets are `Match` objects. # Here, we have an array of these. -say $0; # The same as above. +say $0; # The same as above. -## Our capture is `$0` because it's the first and only one capture in the +## Our capture is `$0` because it's the first and only one capture in the ## regexp. You might be wondering why it's an array, and the answer is simple: -## Some capture (indexed using `$0`, `$/[0]` or a named one) will be an array -## IFF it can have more than one element -## (so, with `*`, `+` and `**` (whatever the operands), but not with `?`). +## Some captures (indexed using `$0`, `$/[0]` or a named one) will be an array +## if and only if they can have more than one element. Thus any capture with +## `*`, `+` and `**` (whatever the operands), but not with `?`. ## Let's use examples to see that: ## Note: We quoted A B C to demonstrate that the whitespace between them isn't -## significant. If we want the whitespace to *be* significant there, we +## significant. If we want the whitespace to *be* significant there, we ## can use the :sigspace modifier. -so 'fooABCbar' ~~ / foo ( "A" "B" "C" )? bar /; # `True` -say $/[0]; #=> ｢ABC｣ +say so 'fooABCbar' ~~ / foo ( "A" "B" "C" )? bar /; #=> `True` +say $/[0]; #=> ｢ABC｣ say $0.WHAT; #=> (Match) # There can't be more than one, so it's only a single match object. -so 'foobar' ~~ / foo ( "A" "B" "C" )? bar /; #=> True +say so 'foobar' ~~ / foo ( "A" "B" "C" )? bar /; #=> True say $0.WHAT; #=> (Any) # This capture did not match, so it's empty -so 'foobar' ~~ / foo ( "A" "B" "C" ) ** 0..1 bar /; # `True` +so 'foobar' ~~ / foo ( "A" "B" "C" ) ** 0..1 bar /; #=> `True` say $0.WHAT; #=> (Array) # A specific quantifier will always capture an Array, - # may it be a range or a specific value (even 1). + # be a range or a specific value (even 1). -## The captures are indexed per nesting. This means a group in a group will be +## The captures are indexed per nesting. This means a group in a group will be ## nested under its parent group: `$/[0][0]`, for this code: 'hello-~-world' ~~ / ( 'hello' ( <[ \- \~ ]> + ) ) 'world' /; -say $/[0].Str; #=> hello~ +say $/[0].Str; #=> hello~ say $/[0][0].Str; #=> ~ -## This stems from a very simple fact: `$/` does not contain strings, integers -## or arrays, it only contains match objects. These contain the `.list`, `.hash` -## and `.Str` methods. (but you can also just use `match` for hash access -## and `match[idx]` for array access) +## This stems from a very simple fact: `$/` does not contain strings, integers +## or arrays, it only contains Match objects. These contain the `.list`, `.hash` +## and `.Str` methods but you can also just use `match` for hash access +## and `match[idx]` for array access. say $/[0].list.perl; #=> (Match.new(...),).list - # We can see it's a list of Match objects. Those contain - # a bunch of infos: where the match started/ended, - # the "ast" (see actions later), etc. + # We can see it's a list of Match objects. These contain + # a bunch of info: where the match started/ended, + # the "ast" (see actions later), etc. # You'll see named capture below with grammars. -## Alternatives - the `or` of regexps +## Alternation - the `or` of regexps ## WARNING: They are DIFFERENT from PCRE regexps. -so 'abc' ~~ / a [ b | y ] c /; # `True`. Either "b" or "y". -so 'ayc' ~~ / a [ b | y ] c /; # `True`. Obviously enough ... - -## The difference between this `|` and the one you're used to is LTM. -## LTM means "Longest Token Matching". This means that the engine will always -## try to match as much as possible in the strng -'foo' ~~ / fo | foo /; # `foo`, because it's longer. -## To decide which part is the "longest", it first splits the regex in +say so 'abc' ~~ / a [ b | y ] c /; #=> `True`. Either "b" or "y". +say so 'ayc' ~~ / a [ b | y ] c /; #=> `True`. Obviously enough... + +## The difference between this `|` and the one you're used to is +## LTM ("Longest Token Matching"). This means that the engine will always +## try to match as much as possible in the string. +say 'foo' ~~ / fo | foo /; #=> `foo`, instead of `fo`, because it's longer. + +## To decide which part is the "longest", it first splits the regex in ## two parts: ## The "declarative prefix" (the part that can be statically analyzed) -## and the procedural parts. -## Declarative prefixes include alternations (`|`), conjunctions (`&`), -## sub-rule calls (not yet introduced), literals, characters classes and +## and the procedural parts: +## - The declarative prefixes include alternations (`|`), conjunctions (`&`), +## sub-rule calls (not yet introduced), literals, characters classes and ## quantifiers. -## The latter include everything else: back-references, code assertions, -## and other things that can't traditionnaly be represented by normal regexps. +## - The procedural part include everything else: back-references, +## code assertions, and other things that can't traditionnaly be represented +## by normal regexps. ## ## Then, all the alternatives are tried at once, and the longest wins. ## Examples: @@ -1639,109 +1806,110 @@ so 'ayc' ~~ / a [ b | y ] c /; # `True`. Obviously enough ... ## DECLARATIVE (nested groups are not a problem) / \s* [ \w & b ] [ c | d ] /; ## However, closures and recursion (of named regexps) are procedural. -## ... There are also more complicated rules, like specificity -## (literals win over character classes) +## There are also more complicated rules, like specificity (literals win over +## character classes). ## Note: the first-matching `or` still exists, but is now spelled `||` -'foo' ~~ / fo || foo /; # `fo` now. +say 'foo' ~~ / fo || foo /; #=> `fo` now. ``` ## Extra: the MAIN subroutine ```perl6 -## The `MAIN` subroutine is called when you run a Perl 6 file directly. -## It's very powerful, because Perl 6 actually parses the arguments -## and pass them as such to the sub. It also handles named argument (`--foo`) -## and will even go as far as to autogenerate a `--help` -sub MAIN($name) { say "Hello, $name !" } +## The `MAIN` subroutine is called when you run a Perl 6 file directly. It's +## very powerful, because Perl 6 actually parses the arguments and pass them +## as such to the sub. It also handles named argument (`--foo`) and will even +## go as far as to autogenerate a `--help` flag. +sub MAIN($name) { + say "Hello, $name!"; +} ## This produces: -## $ perl6 cli.pl -## Usage: -## t.pl +## $ perl6 cli.pl +## Usage: +## t.pl ## And since it's a regular Perl 6 sub, you can have multi-dispatch: ## (using a "Bool" for the named argument so that we can do `--replace` -## instead of `--replace=1`) +## instead of `--replace=1`. The presence of `--replace` indicates truthness +## while its absence falseness). + subset File of Str where *.IO.d; # convert to IO object to check the file exists multi MAIN('add', $key, $value, Bool :$replace) { ... } multi MAIN('remove', $key) { ... } multi MAIN('import', File, Str :$as) { ... } # omitting parameter name + ## This produces: -## $ perl6 cli.pl -## Usage: -## t.pl [--replace] add -## t.pl remove -## t.pl [--as=] import (File) -## As you can see, this is *very* powerful. -## It even went as far as to show inline the constants. -## (the type is only displayed if the argument is `$`/is named) +## $ perl6 cli.pl +## Usage: +## cli.p6 [--replace] add +## cli.p6 remove +## cli.p6 [--as=] import + +## As you can see, this is *very* powerful. It even went as far as to show inline +## the constants (the type is only displayed if the argument is `$`/is named). ``` ## APPENDIX A: ### List of things ```perl6 -## It's considered by now you know the Perl6 basics. -## This section is just here to list some common operations, -## but which are not in the "main part" of the tutorial to bloat it up +## It's assumed by now you know the Perl6 basics. This section is just here to +## list some common operations, but which are not in the "main part" of the +## tutorial to avoid bloating it up. ## Operators - -## * Sort comparison -## They return one value of the `Order` enum : `Less`, `Same` and `More` -## (which numerify to -1, 0 or +1). -1 <=> 4; # sort comparison for numerics -'a' leg 'b'; # sort comparison for string -$obj eqv $obj2; # sort comparison using eqv semantics - -## * Generic ordering -3 before 4; # True -'b' after 'a'; # True - -## * Short-circuit default operator -## Like `or` and `||`, but instead returns the first *defined* value : -say Any // Nil // 0 // 5; #=> 0 - -## * Short-circuit exclusive or (XOR) -## Returns `True` if one (and only one) of its arguments is true -say True ^^ False; #=> True -## * Flip Flop -## The flip flop operators (`ff` and `fff`, equivalent to P5's `..`/`...`). -## are operators that take two predicates to test: -## They are `False` until their left side returns `True`, then are `True` until -## their right side returns `True`. -## Like for ranges, you can exclude the iteration when it became `True`/`False` -## by using `^` on either side. -## Let's start with an example : +## Sort comparison - they return one value of the `Order` enum: `Less`, `Same` +## and `More` (which numerify to -1, 0 or +1 respectively). +1 <=> 4; # sort comparison for numerics +'a' leg 'b'; # sort comparison for string +$obj eqv $obj2; # sort comparison using eqv semantics + +## Generic ordering +3 before 4; # True +'b' after 'a'; # True + +## Short-circuit default operator - similar to `or` and `||`, but instead +## returns the first *defined* value: +say Any // Nil // 0 // 5; #=> 0 + +## Short-circuit exclusive or (XOR) - returns `True` if one (and only one) of +## its arguments is true +say True ^^ False; #=> True + +## Flip flops - these operators (`ff` and `fff`, equivalent to P5's `..` +## and `...`) are operators that take two predicates to test: They are `False` +## until their left side returns `True`, then are `True` until their right +## side returns `True`. Similar to ranges, you can exclude the iteration when +## it become `True`/`False` by using `^` on either side. Let's start with an +## example : for { - # by default, `ff`/`fff` smart-match (`~~`) against `$_`: - if 'met' ^ff 'meet' { # Won't enter the if for "met" - # (explained in details below). - .say - } + # by default, `ff`/`fff` smart-match (`~~`) against `$_`: + if 'met' ^ff 'meet' { # Won't enter the if for "met" + .say # (explained in details below). + } - if rand == 0 ff rand == 1 { # compare variables other than `$_` - say "This ... probably will never run ..."; - } + if rand == 0 ff rand == 1 { # compare variables other than `$_` + say "This ... probably will never run ..."; + } } -## This will print "young hero we shall meet" (excluding "met"): -## the flip-flop will start returning `True` when it first encounters "met" -## (but will still return `False` for "met" itself, due to the leading `^` -## on `ff`), until it sees "meet", which is when it'll start returning `False`. - -## The difference between `ff` (awk-style) and `fff` (sed-style) is that -## `ff` will test its right side right when its left side changes to `True`, -## and can get back to `False` right away -## (*except* it'll be `True` for the iteration that matched) - -## While `fff` will wait for the next iteration to -## try its right side, once its left side changed: + +## This will print "young hero we shall meet" (excluding "met"): the flip-flop +## will start returning `True` when it first encounters "met" (but will still +## return `False` for "met" itself, due to the leading `^` on `ff`), until it +## sees "meet", which is when it'll start returning `False`. + +## The difference between `ff` (awk-style) and `fff` (sed-style) is that `ff` +## will test its right side right when its left side changes to `True`, and can +## get back to `False` right away (*except* it'll be `True` for the iteration +## that matched) while `fff` will wait for the next iteration to try its right +## side, once its left side changed: .say if 'B' ff 'B' for ; #=> B B # because the right-hand-side was tested # directly (and returned `True`). - # "B"s are printed since it matched that - # time (it just went back to `False` + # "B"s are printed since it matched that + # time (it just went back to `False` # right away). .say if 'B' fff 'B' for ; #=> B C B # The right-hand-side wasn't tested until @@ -1750,50 +1918,49 @@ for { ## A flip-flop can change state as many times as needed: for { - .say if $_ eq 'start' ^ff^ $_ eq 'stop'; # exclude both "start" and "stop", - #=> "print it print again" + .say if $_ eq 'start' ^ff^ $_ eq 'stop'; # exclude both "start" and "stop", + #=> "print it print again" } -## You might also use a Whatever Star, -## which is equivalent to `True` for the left side or `False` for the right: +## You might also use a Whatever Star, which is equivalent to `True` for the +## left side or `False` for the right: for (1, 3, 60, 3, 40, 60) { # Note: the parenthesis are superfluous here # (sometimes called "superstitious parentheses") - .say if $_ > 50 ff *; # Once the flip-flop reaches a number greater than 50, - # it'll never go back to `False` - #=> 60 3 40 60 + .say if $_ > 50 ff *; # Once the flip-flop reaches a number greater + # than 50, it'll never go back to `False` + #=> 60 3 40 60 } -## You can also use this property to create an `If` -## that'll not go through the first time : +## You can also use this property to create an `if` that'll not go through the +## first time: for { - .say if * ^ff *; # the flip-flop is `True` and never goes back to `False`, - # but the `^` makes it *not run* on the first iteration - #=> b c + .say if * ^ff *; # the flip-flop is `True` and never goes back to `False`, + # but the `^` makes it *not run* on the first iteration + #=> b c } - -## - `===` is value identity and uses `.WHICH` on the objects to compare them -## - `=:=` is container identity and uses `VAR()` on the objects to compare them - +## The `===` operator is the value identity operator and uses `.WHICH` on the +## objects to compare them while `=:=` is the container identity operator +## and uses `VAR()` on the objects to compare them. ``` If you want to go further, you can: - Read the [Perl 6 Docs](https://docs.perl6.org/). This is a great - resource on Perl6. If you are looking for something, use the search bar. + resource on Perl6. If you are looking for something, use the search bar. This will give you a dropdown menu of all the pages referencing your search - term (Much better than using Google to find Perl 6 documents!) + term (Much better than using Google to find Perl 6 documents!). - Read the [Perl 6 Advent Calendar](http://perl6advent.wordpress.com/). This - is a great source of Perl 6 snippets and explanations. If the docs don't + is a great source of Perl 6 snippets and explanations. If the docs don't describe something well enough, you may find more detailed information here. This information may be a bit older but there are many great examples and - explanations. Posts stopped at the end of 2015 when the language was declared + explanations. Posts stopped at the end of 2015 when the language was declared stable and Perl 6.c was released. - - Come along on `#perl6` at `irc.freenode.net`. The folks here are + - Come along on `#perl6` at `irc.freenode.net`. The folks here are always helpful. - - Check the [source of Perl 6's functions and - classes](https://github.com/rakudo/rakudo/tree/nom/src/core). Rakudo is + - Check the [source of Perl 6's functions and + classes](https://github.com/rakudo/rakudo/tree/nom/src/core). Rakudo is mainly written in Perl 6 (with a lot of NQP, "Not Quite Perl", a Perl 6 subset easier to implement and optimize). - - Read [the language design documents](http://design.perl6.org). They explain + - Read [the language design documents](http://design.perl6.org). They explain P6 from an implementor point-of-view, but it's still very interesting. -- cgit v1.2.3 From 06216f24c9d1bf30137f54b12abe59b67acfdc2e Mon Sep 17 00:00:00 2001 From: b-xor-a <43441509+b-xor-a@users.noreply.github.com> Date: Thu, 4 Jul 2019 14:28:52 +0300 Subject: Fixed behavior of postfix ++ The postfix ++ operator increments its argument but returns its old value. --- perl6.html.markdown | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) (limited to 'perl6.html.markdown') diff --git a/perl6.html.markdown b/perl6.html.markdown index cb64b646..6b0df0d4 100644 --- a/perl6.html.markdown +++ b/perl6.html.markdown @@ -247,11 +247,12 @@ concat3(|@array); #=> a, b, c ## arguments. If you really need to, you can ask for a mutable container by ## using the `is rw` trait: sub mutate( $n is rw ) { - $n++; + $n++; # postfix ++ operator increments its argument but returns its old value } my $m = 42; -mutate $m; #=> 43 +mutate $m; # the value is incremented but the old value is returned + #=> 42 say $m; #=> 43 ## This works because we are passing the container $m to the `mutate` sub. -- cgit v1.2.3 From c709f1dcbbc3f21d8aca2102fd74f9304753b775 Mon Sep 17 00:00:00 2001 From: Felix Ostmann Date: Tue, 6 Aug 2019 10:44:37 +0200 Subject: Object Model example mixed old/new code/comments --- perl6.html.markdown | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) (limited to 'perl6.html.markdown') diff --git a/perl6.html.markdown b/perl6.html.markdown index 6b0df0d4..1304869b 100644 --- a/perl6.html.markdown +++ b/perl6.html.markdown @@ -885,7 +885,7 @@ say_dyn(); #=> 1 100 We changed the value of $*dyn_scoped_2 in class Human { has Str $.name; # `$.name` is immutable but with an accessor method. - has Str $.bcountry; # Use `$!bplace` to modify it inside the class. + has Str $.bcountry; # Use `$!bcountry` to modify it inside the class. has Str $.ccountry is rw; # This attribute can be modified from outside. has Int $!age = 0; # A private attribute with default value. @@ -911,12 +911,12 @@ class Human { } }; -## Create a new instance of Human class with $.attrib set to 5. +## Create a new instance of Human class. ## Note: you can't set private-attribute from here (more later on). my $person1 = Human.new( name => "Jord", - bcountry = "Iceland", - ccountry => "Iceland" + bcountry = "Togo", + ccountry => "Togo" ); say $person1.name; #=> Jord -- cgit v1.2.3 From f0f161981f2e3d35967878b6a7a2c71de75b2b64 Mon Sep 17 00:00:00 2001 From: Amans Tofu Date: Fri, 30 Aug 2019 17:22:27 +0800 Subject: [Perl6/en]Modify an error about the Range constructor (#3612) [Perl6/en] Modify an error about the Range constructor --- perl6.html.markdown | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-) (limited to 'perl6.html.markdown') diff --git a/perl6.html.markdown b/perl6.html.markdown index 1304869b..c7fde218 100644 --- a/perl6.html.markdown +++ b/perl6.html.markdown @@ -499,10 +499,19 @@ say False ~~ True; #=> True ## Range constructor ##------------------ -3 .. 7; # 3 to 7, both included +3 .. 7; # 3 to 7, both included. 3 ..^ 7; # 3 to 7, exclude right endpoint. -3 ^.. 7; # 3 to 7, exclude left endpoint. Same as `4..7`. -3 ^..^ 7; # 3 to 7, exclude both endpoints. Same as `4..6`. +3 ^.. 7; # 3 to 7, exclude left endpoint. +3 ^..^ 7; # 3 to 7, exclude both endpoints. + # 3 ^.. 7 almost like 4 .. 7 when we only consider integers. + # But when we consider decimals : +3.5 ~~ 4 .. 7; # False +3.5 ~~ 3 ^.. 7; # True, This Range also contains decimals greater than 3. + # We describe it like this in some math books: 3.5 ∈ (3,7] + # If you don’t want to understand the concept of interval + # for the time being. At least we should know： +3 ^.. 7 ~~ 4 .. 7; # False + ## This also works as a shortcut for `0..^N`: ^10; # means 0..^10 -- cgit v1.2.3 From 6688d18f61fd0e54ef2513cc2c9f0c7b336cf799 Mon Sep 17 00:00:00 2001 From: "Luis F. Uceta" Date: Sat, 7 Dec 2019 13:03:36 -0500 Subject: Add changes regarding rename and more: (#3758) - Replace mentions of Perl 6 with Raku (See https://github.com/perl6/problem-solving/blob/master/solutions/language/Path-to-Raku.md) - Document's sections is now part of the resulting raku file - The resulting Raku file can now be executed without runtime/compile-time errors - Some examples had minor updates or fixes - Update links, extensions and commands. --- perl6.html.markdown | 1976 --------------------------------------------------- 1 file changed, 1976 deletions(-) delete mode 100644 perl6.html.markdown (limited to 'perl6.html.markdown') diff --git a/perl6.html.markdown b/perl6.html.markdown deleted file mode 100644 index c7fde218..00000000 --- a/perl6.html.markdown +++ /dev/null @@ -1,1976 +0,0 @@ ---- -category: language -language: perl6 -filename: learnperl6.p6 -contributors: - - ["vendethiel", "http://github.com/vendethiel"] - - ["Samantha McVey", "https://cry.nu"] ---- - -Perl 6 is a highly capable, feature-rich programming language made for at -least the next hundred years. - -The primary Perl 6 compiler is called [Rakudo](http://rakudo.org), which runs on -the JVM and [the MoarVM](http://moarvm.com). - -Meta-note: double pound signs (`##`) are used to indicate paragraphs, -while single pound signs (`#`) indicate notes. - -`#=>` represents the output of a command. - -```perl6 -# Single line comments start with a pound sign. - -#`( Multiline comments use #` and a quoting construct. - (), [], {}, 「」, etc, will work. -) - -# Use the same syntax for multiline comments to embed comments. -for #`(each element in) @array { - put #`(or print element) $_ #`(with newline); -} -``` - -## Variables - -```perl6 -## In Perl 6, you declare a lexical variable using the `my` keyword: -my $variable; -## Perl 6 has 3 basic types of variables: scalars, arrays, and hashes. -``` - -### Scalars - -```perl6 -# Scalars represent a single value. They start with the `$` sigil: -my $str = 'String'; - -# Double quotes allow for interpolation (which we'll see later): -my $str2 = "String"; - -## Variable names can contain but not end with simple quotes and dashes, -## and can contain (and end with) underscores: -my $person's-belongings = 'towel'; # this works! - -my $bool = True; # `True` and `False` are Perl 6's boolean values. -my $inverse = !$bool; # Invert a bool with the prefix `!` operator. -my $forced-bool = so $str; # And you can use the prefix `so` operator -$forced-bool = ?$str; # to turn its operand into a Bool. Or use `?`. -``` - -### Arrays and Lists - -```perl6 -## Arrays represent multiple values. An array variable starts with the `@` -## sigil. Unlike lists, from which arrays inherit, arrays are mutable. - -my @array = 'a', 'b', 'c'; -# equivalent to: -my @letters = ; # array of words, delimited by space. - # Similar to perl5's qw, or Ruby's %w. -@array = 1, 2, 3; - -say @array[2]; # Array indices start at 0. Here the third element - # is being accessed. - -say "Interpolate an array using []: @array[]"; -#=> Interpolate an array using []: 1 2 3 - -@array[0] = -1; # Assigning a new value to an array index -@array[0, 1] = 5, 6; # Assigning multiple values - -my @keys = 0, 2; -@array[@keys] = @letters; # Assignment using an array containing index values -say @array; #=> a 6 b -``` - -### Hashes, or key-value Pairs. - -```perl6 -## Hashes are pairs of keys and values. You can construct a `Pair` object -## using the syntax `Key => Value`. Hash tables are very fast for lookup, -## and are stored unordered. Keep in mind that keys get "flattened" in hash -## context, and any duplicated keys are deduplicated. -my %hash = 'a' => 1, 'b' => 2; - -%hash = a => 1, # keys get auto-quoted when => (fat comma) is used. - b => 2, # Trailing commas are okay. -; - -## Even though hashes are internally stored differently than arrays, -## Perl 6 allows you to easily create a hash from an even numbered array: -%hash = ; # Or: -%hash = "key1", "value1", "key2", "value2"; - -%hash = key1 => 'value1', key2 => 'value2'; # same result as above - -## You can also use the "colon pair" syntax. This syntax is especially -## handy for named parameters that you'll see later. -%hash = :w(1), # equivalent to `w => 1` - :truey, # equivalent to `:truey(True)` or `truey => True` - :!falsey, # equivalent to `:falsey(False)` or `falsey => False` -; -## The :truey and :!falsey constructs are known as the -## `True` and `False` shortcuts respectively. - -say %hash{'key1'}; # You can use {} to get the value from a key. -say %hash; # If it's a string without spaces, you can actually use - # <> (quote-words operator). `{key1}` doesn't work, - # as Perl6 doesn't have barewords. -``` - -## Subs - -```perl6 -## Subroutines, or functions as most other languages call them, are -## created with the `sub` keyword. -sub say-hello { say "Hello, world" } - -## You can provide (typed) arguments. If specified, the type will be checked -## at compile-time if possible, otherwise at runtime. -sub say-hello-to( Str $name ) { - say "Hello, $name !"; -} - -## A sub returns the last value of the block. Similarly, the semicolon in -## the last can be omitted. -sub return-value { 5 } -say return-value; # prints 5 - -sub return-empty { } -say return-empty; # prints Nil - -## Some control flow structures produce a value, like `if`: -sub return-if { - if True { "Truthy" } -} -say return-if; # prints Truthy - -## Some don't, like `for`: -sub return-for { - for 1, 2, 3 { 'Hi' } -} -say return-for; # prints Nil - -## Positional arguments are required by default. To make them optional, use -## the `?` after the parameters' names. -sub with-optional( $arg? ) { - # This sub returns `(Any)` (Perl's null-like value) if - # no argument is passed. Otherwise, it returns its argument. - $arg; -} -with-optional; # returns Any -with-optional(); # returns Any -with-optional(1); # returns 1 - -## You can also give them a default value when they're not passed. -## Required parameters must come before optional ones. -sub greeting( $name, $type = "Hello" ) { - say "$type, $name!"; -} - -greeting("Althea"); #=> Hello, Althea! -greeting("Arthur", "Good morning"); #=> Good morning, Arthur! - -## You can also, by using a syntax akin to the one of hashes -## (yay unified syntax !), pass *named* arguments to a `sub`. They're -## optional, and will default to "Any". -sub with-named( $normal-arg, :$named ) { - say $normal-arg + $named; -} -with-named(1, named => 6); #=> 7 - -## There's one gotcha to be aware of, here: If you quote your key, Perl 6 -## won't be able to see it at compile time, and you'll have a single `Pair` -## object as a positional parameter, which means -## `with-named(1, 'named' => 6);` fails. - -with-named(2, :named(5)); #=> 7 - -## To make a named argument mandatory, you can append `!` to the parameter, -## which is the inverse of `?`: -sub with-mandatory-named( :$str! ) { - say "$str!"; -} -with-mandatory-named(str => "My String"); #=> My String! -with-mandatory-named; # runtime error:"Required named parameter not passed" -with-mandatory-named(3);# runtime error:"Too many positional parameters passed" - -## If a sub takes a named boolean argument... -sub takes-a-bool( $name, :$bool ) { - say "$name takes $bool"; -} -## ... you can use the same "short boolean" hash syntax: -takes-a-bool('config', :bool); #=> config takes True -takes-a-bool('config', :!bool); #=> config takes False - -## You can also provide your named arguments with default values: -sub named-def( :$def = 5 ) { - say $def; -} -named-def; #=> 5 -named-def(def => 15); #=> 15 - -## Since you can omit parenthesis to call a function with no arguments, -## you need `&` in the name to store `say-hello` in a variable. This means -## `&say-hello` is a code object and not a subroutine call. -my &s = &say-hello; -my &other-s = sub { say "Anonymous function!" } - -## A sub can have a "slurpy" parameter, or "doesn't-matter-how-many". For -## this, you must use `*@` (slurpy) which will "take everything else". You can -## have as many parameters *before* a slurpy one, but not *after*. -sub as-many($head, *@rest) { - say @rest.join(' / ') ~ " !"; -} -say as-many('Happy', 'Happy', 'Birthday');#=> Happy / Birthday ! - # Note that the splat (the *) did not - # consume the parameter before it. - -## You can call a function with an array using the "argument list flattening" -## operator `|` (it's not actually the only role of this operator, -## but it's one of them). -sub concat3($a, $b, $c) { - say "$a, $b, $c"; -} -concat3(|@array); #=> a, b, c - # `@array` got "flattened" as a part of the argument list -``` - -## Containers - -```perl6 -## In Perl 6, values are actually stored in "containers". The assignment -## operator asks the container on the left to store the value on its right. -## When passed around, containers are marked as immutable which means that, -## in a function, you'll get an error if you try to mutate one of your -## arguments. If you really need to, you can ask for a mutable container by -## using the `is rw` trait: -sub mutate( $n is rw ) { - $n++; # postfix ++ operator increments its argument but returns its old value -} - -my $m = 42; -mutate $m; # the value is incremented but the old value is returned - #=> 42 -say $m; #=> 43 - -## This works because we are passing the container $m to the `mutate` sub. -## If we try to just pass a number instead of passing a variable it won't work -## because there is no container being passed and integers are immutable by -## themselves: - -mutate 42; # Parameter '$n' expected a writable container, but got Int value - -## Similar error would be obtained, if a bound variable is passed to -## to the subroutine: - -my $v := 50; # binding 50 to the variable $v -mutate $v; # Parameter '$n' expected a writable container, but got Int value - -## If what you want is a copy instead, use the `is copy` trait which will -## cause the argument to be copied and allow you to modify the argument -## inside the routine. - -## A sub itself returns a container, which means it can be marked as rw: -my $x = 42; -sub x-store() is rw { $x } -x-store() = 52; # in this case, the parentheses are mandatory - # (else Perl 6 thinks `x-store` is an identifier) -say $x; #=> 52 -``` - -## Control Flow Structures - -### Conditionals - -```perl6 -## - `if` -## Before talking about `if`, we need to know which values are "Truthy" -## (represent True), and which are "Falsey" (represent False). Only these -## values are Falsey: 0, (), {}, "", Nil, A type (like `Str` or `Int`) and -## of course False itself. Any other value is Truthy. -if True { - say "It's true!"; -} - -unless False { - say "It's not false!"; -} - -## As you can see, you don't need parentheses around conditions. However, you -## do need the curly braces around the "body" block. For example, -## `if (true) say;` doesn't work. - -## You can also use their statement modifier (postfix) versions: -say "Quite truthy" if True; #=> Quite truthy -say "Quite falsey" unless False; #=> Quite falsey - -## - Ternary operator, "x ?? y !! z" -## This returns $value-if-true if the condition is true and $value-if-false -## if it is false. -## my $result = condition ?? $value-if-true !! $value-if-false; - -my $age = 30; -say $age > 18 ?? "You are an adult" !! "You are under 18"; -#=> You are an adult -``` - -### given/when, or Perl 6's switch construct - -```perl6 -## `given...when` looks like other languages' `switch`, but is much more -## powerful thanks to smart matching and Perl 6's "topic variable", $_. -## -## The topic variable $_ contains the default argument of a block, a loop's -## current iteration (unless explicitly named), etc. -## -## `given` simply puts its argument into `$_` (like a block would do), -## and `when` compares it using the "smart matching" (`~~`) operator. -## -## Since other Perl 6 constructs use this variable (as said before, like `for`, -## blocks, etc), this means the powerful `when` is not only applicable along -## with a `given`, but instead anywhere a `$_` exists. - -given "foo bar" { - say $_; #=> foo bar - when /foo/ { # Don't worry about smart matching yet. Just know - say "Yay !"; # `when` uses it. This is equivalent to `if $_ ~~ /foo/`. - - } - when $_.chars > 50 { # smart matching anything with True is True, - # i.e. (`$a ~~ True`) - # so you can also put "normal" conditionals. - # This `when` is equivalent to this `if`: - # `if $_ ~~ ($_.chars > 50) {...}` - # which means: `if $_.chars > 50 {...}` - say "Quite a long string !"; - } - default { # same as `when *` (using the Whatever Star) - say "Something else" - } -} -``` - -### Looping constructs - -```perl6 -## - `loop` is an infinite loop if you don't pass it arguments, but can also -## be a C-style `for` loop: -loop { - say "This is an infinite loop !"; - last; # last breaks out of the loop, like - # the `break` keyword in other languages -} - -loop (my $i = 0; $i < 5; $i++) { - next if $i == 3; # `next` skips to the next iteration, like `continue` - # in other languages. Note that you can also use postfix - # conditionals, loops, etc. - say "This is a C-style for loop!"; -} - -## - `for` - Iterating through an array - -my @array = 1, 2, 6, 7, 3; - -## Accessing the array's elements with the topic variable $_. -for @array { - say "I've got $_ !"; -} - -## Accessing the array's elements with a "pointy block", `->`. -## Here each element is read-only. -for @array -> $variable { - say "I've got $variable !"; -} - -## Accessing the array's elements with a "doubly pointy block", `<->`. -## Here each element is read-write so mutating `$variable` mutates -## that element in the array. -for @array <-> $variable { - say "I've got $variable !"; -} - -## As we saw with given, a for loop's default "current iteration" variable -## is `$_`. That means you can use `when` in a `for`loop just like you were -## able to in a `given`. -for @array { - say "I've got $_"; - - .say; # This is also allowed. A dot call with no "topic" (receiver) - # is sent to `$_` by default - $_.say; # This is equivalent to the above statement. -} - -for @array { - # You can... - next if $_ == 3; # Skip to the next iteration (`continue` in C-like lang.) - redo if $_ == 4; # Re-do iteration, keeping the same topic variable (`$_`) - last if $_ == 5; # Or break out of loop (like `break` in C-like lang.) -} - -## The "pointy block" syntax isn't specific to the `for` loop. It's just a way -## to express a block in Perl 6. -sub long-computation { "Finding factors of large primes" } -if long-computation() -> $result { - say "The result is $result."; -} -``` - -## Operators - -```perl6 -## Since Perl languages are very much operator-based languages, Perl 6 -## operators are actually just funny-looking subroutines, in syntactic -## categories, like infix:<+> (addition) or prefix: (bool not). - -## The categories are: -## - "prefix": before (like `!` in `!True`). -## - "postfix": after (like `++` in `$a++`). -## - "infix": in between (like `*` in `4 * 3`). -## - "circumfix": around (like `[`-`]` in `[1, 2]`). -## - "post-circumfix": around, after another term (like `{`-`}` in -## `%hash{'key'}`) - -## The associativity and precedence list are explained below. - -## Alright, you're set to go! - -## Equality Checking -##------------------ - -## - `==` is numeric comparison -3 == 4; #=> False -3 != 4; #=> True - -## - `eq` is string comparison -'a' eq 'b'; #=> False -'a' ne 'b'; #=> True, not equal -'a' !eq 'b'; #=> True, same as above - -## - `eqv` is canonical equivalence (or "deep equality") -(1, 2) eqv (1, 3); #=> False -(1, 2) eqv (1, 2); #=> True -Int === Int #=> True - -## - `~~` is the smart match operator -## Aliases the left hand side to $_ and then evaluates the right hand side. -## Here are some common comparison semantics: - -## String or numeric equality -'Foo' ~~ 'Foo'; # True if strings are equal. -12.5 ~~ 12.50; # True if numbers are equal. - -## Regex - For matching a regular expression against the left side. -## Returns a `Match` object, which evaluates as True if regexp matches. - -my $obj = 'abc' ~~ /a/; -say $obj; #=> ｢a｣ -say $obj.WHAT; #=> (Match) - -## Hashes -'key' ~~ %hash; # True if key exists in hash. - -## Type - Checks if left side "is of type" (can check superclasses and -## roles). -say 1 ~~ Int; #=> True - -## Smart-matching against a boolean always returns that boolean -## (and will warn). -say 1 ~~ True; #=> True -say False ~~ True; #=> True - -## General syntax is `$arg ~~ &bool-returning-function;`. For a complete list -## of combinations, use this table: -## http://perlcabal.org/syn/S03.html#Smart_matching - -## Of course, you also use `<`, `<=`, `>`, `>=` for numeric comparison. -## Their string equivalent are also available: `lt`, `le`, `gt`, `ge`. -3 > 4; # False -3 >= 4; # False -3 < 4; # True -3 <= 4; # True -'a' gt 'b'; # False -'a' ge 'b'; # False -'a' lt 'b'; # True -'a' le 'b'; # True - - -## Range constructor -##------------------ -3 .. 7; # 3 to 7, both included. -3 ..^ 7; # 3 to 7, exclude right endpoint. -3 ^.. 7; # 3 to 7, exclude left endpoint. -3 ^..^ 7; # 3 to 7, exclude both endpoints. - # 3 ^.. 7 almost like 4 .. 7 when we only consider integers. - # But when we consider decimals : -3.5 ~~ 4 .. 7; # False -3.5 ~~ 3 ^.. 7; # True, This Range also contains decimals greater than 3. - # We describe it like this in some math books: 3.5 ∈ (3,7] - # If you don’t want to understand the concept of interval - # for the time being. At least we should know： -3 ^.. 7 ~~ 4 .. 7; # False - - -## This also works as a shortcut for `0..^N`: -^10; # means 0..^10 - -## This also allows us to demonstrate that Perl 6 has lazy/infinite arrays, -## using the Whatever Star: -my @array = 1..*; # 1 to Infinite! Equivalent to `1..Inf`. -say @array[^10]; # You can pass ranges as subscripts and it'll return - # an array of results. This will print - # "1 2 3 4 5 6 7 8 9 10" (and not run out of memory!) - -## Note: when reading an infinite list, Perl 6 will "reify" the elements -## it needs, then keep them in memory. They won't be calculated more than once. -## It also will never calculate more elements that are needed. - -## An array subscript can also be a closure. It'll be called with the length -## as the argument: -say join(' ', @array[15..*]); #=> 15 16 17 18 19 -## which is equivalent to: -say join(' ', @array[-> $n { 15..$n }]); - -## Note: if you try to do either of those with an infinite array, -## you'll trigger an infinite loop (your program won't finish). - -## You can use that in most places you'd expect, even when assigning to -## an array: -my @numbers = ^20; - -## Here the numbers increase by 6, like an arithmetic sequence; more on the -## sequence (`...`) operator later. -my @seq = 3, 9 ... * > 95; # 3 9 15 21 27 [...] 81 87 93 99; -@numbers[5..*] = 3, 9 ... *; # even though the sequence is infinite, - # only the 15 needed values will be calculated. -say @numbers; #=> 0 1 2 3 4 3 9 15 21 [...] 81 87 - # (only 20 values) - -## and (&&), or (||) -##------------------ -3 && 4; # 4, which is Truthy. Calls `.Bool` on both 3 and 4 and gets `True` - # so it returns 4 since both are `True`. -3 && 0; # 0 -0 && 4; # 0 - -0 || False; # False. Calls `.Bool` on `0` and `False` which are both `False` - # so it retusns `False` since both are `False`. - -## Short-circuit (and tight) versions of the above -## Return the first argument that evaluates to False, or the last argument. - -my ( $a, $b, $c ) = 1, 0, 2; -$a && $b && $c; # Returns 0, the first False value - -## || Returns the first argument that evaluates to True -$b || $a; # 1 - -## And because you're going to want them, you also have compound assignment -## operators: -$a *= 2; # multiply and assignment. Equivalent to $a = $a * 2; -$b %%= 5; # divisible by and assignment. Equivalent to $b = $b %% 2; -$c div= 3; # return divisor and assignment. Equivalent to $c = $c div 3; -$d mod= 4; # return remainder and assignment. Equivalent to $d = $d mod 4; -@array .= sort; # calls the `sort` method and assigns the result back -``` - -## More on subs! - -```perl6 -## As we said before, Perl 6 has *really* powerful subs. We're going -## to see a few more key concepts that make them better than in any -## other language :-). -``` - -### Unpacking! - -```perl6 -## Unpacking is the ability to "extract" arrays and keys -## (AKA "destructuring"). It'll work in `my`s and in parameter lists. -my ($f, $g) = 1, 2; -say $f; #=> 1 -my ($, $, $h) = 1, 2, 3; # keep the non-interesting values anonymous (`$`) -say $h; #=> 3 - -my ($head, *@tail) = 1, 2, 3; # Yes, it's the same as with "slurpy subs" -my (*@small) = 1; - -sub unpack_array( @array [$fst, $snd] ) { - say "My first is $fst, my second is $snd! All in all, I'm @array[]."; - # (^ remember the `[]` to interpolate the array) -} -unpack_array(@tail); #=> My first is 2, my second is 3! All in all, I'm 2 3. - - -## If you're not using the array itself, you can also keep it anonymous, -## much like a scalar: -sub first-of-array( @ [$fst] ) { $fst } -first-of-array(@small); #=> 1 -first-of-array(@tail); # Error: "Too many positional parameters passed" - # (which means the array is too big). - -## You can also use a slurp... -sub slurp-in-array(@ [$fst, *@rest]) { # You could keep `*@rest` anonymous - say $fst + @rest.elems; # `.elems` returns a list's length. - # Here, `@rest` is `(3,)`, since `$fst` - # holds the `2`. -} -slurp-in-array(@tail); #=> 3 - -## You could even extract on a slurpy (but it's pretty useless ;-).) -sub fst(*@ [$fst]) { # or simply: `sub fst($fst) { ... }` - say $fst; -} -fst(1); #=> 1 -fst(1, 2); # errors with "Too many positional parameters passed" - -## You can also destructure hashes (and classes, which you'll learn about -## later). The syntax is basically the same as -## `%hash-name (:key($variable-to-store-value-in))`. -## The hash can stay anonymous if you only need the values you extracted. -sub key-of( % (:value($val), :qua($qua)) ) { - say "Got val $val, $qua times."; -} - -## Then call it with a hash. You need to keep the curly braces for it to be a -## hash or use `%()` instead to indicate a hash is being passed. -key-of({value => 'foo', qua => 1}); #=> Got val foo, 1 times. -key-of(%(value => 'foo', qua => 1)); #=> Got val foo, 1 times. -#key-of(%hash); # the same (for an equivalent `%hash`) - -## The last expression of a sub is returned automatically (though you may -## indicate explicitly by using the `return` keyword, of course): -sub next-index( $n ) { - $n + 1; -} -my $new-n = next-index(3); # $new-n is now 4 - -## This is true for everything, except for the looping constructs (due to -## performance reasons): there's no reason to build a list if we're just going to -## discard all the results. If you still want to build one, you can use the -## `do` statement prefix or the `gather` prefix, which we'll see later: - -sub list-of( $n ) { - do for ^$n { # note the range-to prefix operator `^` (`0..^N`) - $_ # current loop iteration known as the "topic" variable - } -} -my @list3 = list-of(3); #=> (0, 1, 2) -``` - -### lambdas (or anonymous subroutines) - -```perl6 -## You can create a lambda with `-> {}` ("pointy block") , -## `{}` ("block") or `sub {}`. - -my &lambda1 = -> $argument { - "The argument passed to this lambda is $argument" -} - -my &lambda2 = { - "The argument passed to this lambda is $_" -} - -my &lambda3 = sub ($argument) { - "The argument passed to this lambda is $argument" -} - -## `-> {}` and `{}` are pretty much the same thing, except that the former can -## take arguments, and that the latter can be mistaken as a hash by the parser. - -## We can, for example, add 3 to each value of an array using the -## `map` function with a lambda: -my @arrayplus3 = map({ $_ + 3 }, @array); # $_ is the implicit argument - -## A sub (`sub {}`) has different semantics than a block (`{}` or `-> {}`): -## A block doesn't have a "function context" (though it can have arguments), -## which means that if you return from it, you're going to return from the -## parent function. Compare: -sub is-in( @array, $elem ) { - # this will `return` out of the `is-in` sub once the condition evaluated - ## to True, the loop won't be run anymore. - map({ return True if $_ == $elem }, @array); -} -## with: -sub truthy-array( @array ) { - # this will produce an array of `True` and `False`: - # (you can also say `anon sub` for "anonymous subroutine") - map(sub ($i) { if $i { return True } else { return False } }, @array); - # ^ the `return` only returns from the anonymous `sub` -} - -## The `anon` declarator can be used to create an anonymous sub from a -## regular subroutine. The regular sub knows its name but its symbol is -## prevented from getting installed in the lexical scope, the method table -## and everywhere else. - -my $anon-sum = anon sub summation(*@a) { [+] *@a } -say $anon-sum.name; #=> summation -say $anon-sum(2, 3, 5); #=> 10 -#say summation; #=> Error: Undeclared routine: ... - -## You can also use the "whatever star" to create an anonymous subroutine. -## (it'll stop at the furthest operator in the current expression) -my @arrayplus3 = map(*+3, @array); # `*+3` is the same as `{ $_ + 3 }` -my @arrayplus3 = map(*+*+3, @array); # Same as `-> $a, $b { $a + $b + 3 }` - # also `sub ($a, $b) { $a + $b + 3 }` -say (*/2)(4); #=> 2 - # Immediately execute the function Whatever created. -say ((*+3)/5)(5); #=> 1.6 - # It works even in parens! - -## But if you need to have more than one argument (`$_`) in a block (without -## wanting to resort to `-> {}`), you can also use the implicit argument -## syntax, `$^`: -map({ $^a + $^b + 3 }, @array); -# which is equivalent to the following which uses a `sub`: -map(sub ($a, $b) { $a + $b + 3 }, @array); - -## The parameters `$^a`, `$^b`, etc. are known as placeholder parameters or -## self-declared positional parameters. They're sorted lexicographically so -## `{ $^b / $^a }` is equivalent `-> $a, $b { $b / $a }`. -``` - -### About types... - -```perl6 -## Perl 6 is gradually typed. This means you can specify the type of your -## variables/arguments/return types, or you can omit the type annotations in -## in which case they'll default to `Any`. Obviously you get access to a few -## base types, like `Int` and `Str`. The constructs for declaring types are -## "subset", "class", "role", etc. which you'll see later. - -## For now, let us examine "subset" which is a "sub-type" with additional -## checks. For example, "a very big integer is an Int that's greater than 500". -## You can specify the type you're subtyping (by default, `Any`), and add -## additional checks with the `where` clause: -subset VeryBigInteger of Int where * > 500; -## Or the set of the whole numbers: -subset WholeNumber of Int where * >= 0; -``` - -### Multiple Dispatch - -```perl6 -## Perl 6 can decide which variant of a `sub` to call based on the type of the -## arguments, or on arbitrary preconditions, like with a type or `where`: - -## with types: -multi sub sayit( Int $n ) { # note the `multi` keyword here - say "Number: $n"; -} -multi sayit( Str $s ) { # a multi is a `sub` by default - say "String: $s"; -} -sayit("foo"); #=> "String: foo" -sayit(25); #=> "Number: 25" -sayit(True); # fails at *compile time* with "calling 'sayit' will never - # work with arguments of types ..." - -## with arbitrary preconditions (remember subsets?): -multi is-big(Int $n where * > 50) { "Yes!" } # using a closure -multi is-big(Int $n where {$_ > 50}) { "Yes!" } # similar to above -multi is-big(Int $ where 10..50) { "Quite." } # Using smart-matching - # (could use a regexp, etc) -multi is-big(Int $) { "No" } - -subset Even of Int where * %% 2; -multi odd-or-even(Even) { "Even" } # The main case using the type. - # We don't name the argument. -multi odd-or-even($) { "Odd" } # "everthing else" hence the $ variable - -## You can even dispatch based on the presence of positional and -## named arguments: -multi with-or-without-you($with) { - say "I wish I could but I can't"; -} -multi with-or-without-you(:$with) { - say "I can live! Actually, I can't."; -} -multi with-or-without-you { - say "Definitely can't live."; -} - -## This is very, very useful for many purposes, like `MAIN` subs (covered -## later), and even the language itself uses it in several places. -## -## - `is`, for example, is actually a `multi sub` named `trait_mod:`, -## and it works off that. -## - `is rw`, is simply a dispatch to a function with this signature: -## sub trait_mod:(Routine $r, :$rw!) {} -## -## (commented out because running this would be a terrible idea!) -``` - -## Scoping - -```perl6 -## In Perl 6, unlike many scripting languages, (such as Python, Ruby, PHP), -## you must declare your variables before using them. The `my` declarator -## you have learned uses "lexical scoping". There are a few other declarators, -## (`our`, `state`, ..., ) which we'll see later. This is called -## "lexical scoping", where in inner blocks, you can access variables from -## outer blocks. -my $file_scoped = 'Foo'; -sub outer { - my $outer_scoped = 'Bar'; - sub inner { - say "$file_scoped $outer_scoped"; - } - &inner; # return the function -} -outer()(); #=> 'Foo Bar' - -## As you can see, `$file_scoped` and `$outer_scoped` were captured. -## But if we were to try and use `$outer_scoped` outside the `outer` sub, -## the variable would be undefined (and you'd get a compile time error). -``` - -## Twigils - -```perl6 -## There are many special `twigils` (composed sigils) in Perl 6. Twigils -## define the variables' scope. -## The * and ? twigils work on standard variables: -## * Dynamic variable -## ? Compile-time variable -## The ! and the . twigils are used with Perl 6's objects: -## ! Attribute (instance attribute) -## . Method (not really a variable) - -## `*` twigil: Dynamic Scope -## These variables use the `*` twigil to mark dynamically-scoped variables. -## Dynamically-scoped variables are looked up through the caller, not through -## the outer scope. - -my $*dyn_scoped_1 = 1; -my $*dyn_scoped_2 = 10; - -sub say_dyn { - say "$*dyn_scoped_1 $*dyn_scoped_2"; -} - -sub call_say_dyn { - my $*dyn_scoped_1 = 25; # Defines $*dyn_scoped_1 only for this sub. - $*dyn_scoped_2 = 100; # Will change the value of the file scoped variable. - say_dyn(); #=> 25 100, $*dyn_scoped 1 and 2 will be looked - # for in the call. - # It uses the value of $*dyn_scoped_1 from inside - # this sub's lexical scope even though the blocks - # aren't nested (they're call-nested). -} -say_dyn(); #=> 1 10 -call_say_dyn(); #=> 25 100 - # Uses $*dyn_scoped_1 as defined in call_say_dyn even though - # we are calling it from outside. -say_dyn(); #=> 1 100 We changed the value of $*dyn_scoped_2 in - # call_say_dyn so now its value has changed. -``` - -## Object Model - -```perl6 -## To call a method on an object, add a dot followed by the method name: -## `$object.method` - -## Classes are declared with the `class` keyword. Attributes are declared -## with the `has` keyword, and methods declared with the `method` keyword. - -## Every attribute that is private uses the ! twigil. For example: `$!attr`. -## Immutable public attributes use the `.` twigil which creates a read-only -## method named after the attribute. In fact, declaring an attribute with `.` -## is equivalent to declaring the same attribute with `!` and then creating -## a read-only method with the attribute's name. However, this is done for us -## by Perl 6 automatically. The easiest way to remember the `$.` twigil is -## by comparing it to how methods are called. - -## Perl 6's object model ("SixModel") is very flexible, and allows you to -## dynamically add methods, change semantics, etc... Unfortunately, these will -## not all be covered here, and you should refer to: -## https://docs.perl6.org/language/objects.html. - -class Human { - has Str $.name; # `$.name` is immutable but with an accessor method. - has Str $.bcountry; # Use `$!bcountry` to modify it inside the class. - has Str $.ccountry is rw; # This attribute can be modified from outside. - has Int $!age = 0; # A private attribute with default value. - - method birthday { - $!age += 1; # Add a year to human's age - } - - method get-age { - return $!age; - } - - # This method is private to the class. Note the `!` before the - # method's name. - method !do-decoration { - return "$!name was born in $!bcountry and now lives in $!ccountry." - } - - # This method is public, just like `birthday` and `get-age`. - method get-info { - self.do-decoration; # Invoking a method on `self` inside the class. - # Use `self!priv-method` for private method. - # Use `self.publ-method` for public method. - } -}; - -## Create a new instance of Human class. -## Note: you can't set private-attribute from here (more later on). -my $person1 = Human.new( - name => "Jord", - bcountry = "Togo", - ccountry => "Togo" -); - -say $person1.name; #=> Jord -say $person1.bcountry; #=> Togo -say $person1.ccountry; #=> Togo - - -# $person1.bcountry = "Mali"; # This fails, because the `has $.bcountry` - # is immutable. Jord can't change his birthplace. -$person1.ccountry = "France"; # This works because the `$.ccountry` is mutable - # (`is rw`). Now Jord's current country is France. - -# Calling methods on the instance objects. -$person1.birthday; #=> 1 -$person1.get-info; #=> Jord was born in Togo and now lives in France. -$person1.do-decoration; # This fails since the method `do-decoration` is - # private. -``` - -### Object Inheritance - -```perl6 -## Perl 6 also has inheritance (along with multiple inheritance). While -## methods are inherited, submethods are not. Submethods are useful for -## object construction and destruction tasks, such as BUILD, or methods that -## must be overridden by subtypes. We will learn about BUILD later on. - -class Parent { - has $.age; - has $.name; - - # This submethod won't be inherited by the Child class. - submethod favorite-color { - say "My favorite color is Blue"; - } - - # This method is inherited - method talk { say "Hi, my name is $!name" } -} - -# Inheritance uses the `is` keyword -class Child is Parent { - method talk { say "Goo goo ga ga" } - # This shadows Parent's `talk` method. - # This child hasn't learned to speak yet! -} - -my Parent $Richard .= new(age => 40, name => 'Richard'); -$Richard.favorite-color; #=> "My favorite color is Blue" -$Richard.talk; #=> "Hi, my name is Richard" -## $Richard is able to access the submethod and he knows how to say his name. - -my Child $Madison .= new(age => 1, name => 'Madison'); -$Madison.talk; #=> "Goo goo ga ga", due to the overridden method. -# $Madison.favorite-color # does not work since it is not inherited. - -## When you use `my T $var`, `$var` starts off with `T` itself in it, -## so you can call `new` on it. -## (`.=` is just the dot-call and the assignment operator: -## `$a .= b` is the same as `$a = $a.b`) -## Also note that `BUILD` (the method called inside `new`) -## will set parent's properties too, so you can pass `val => 5`. -``` - -### Roles, or Mixins - -```perl6 -## Roles are supported too (which are called Mixins in other languages) -role PrintableVal { - has $!counter = 0; - method print { - say $.val; - } -} - -## you "apply" a role (or mixin) with `does` keyword: -class Item does PrintableVal { - has $.val; - - ## When `does`-ed, a `role` literally "mixes in" the class: - ## the methods and attributes are put together, which means a class - ## can access the private attributes/methods of its roles (but - ## not the inverse!): - method access { - say $!counter++; - } - - ## However, this: - ## method print {} - ## is ONLY valid when `print` isn't a `multi` with the same dispatch. - ## (this means a parent class can shadow a child class's `multi print() {}`, - ## but it's an error if a role does) - - ## NOTE: You can use a role as a class (with `is ROLE`). In this case, - ## methods will be shadowed, since the compiler will consider `ROLE` - ## to be a class. -} -``` - -## Exceptions - -```perl6 -## Exceptions are built on top of classes, in the package `X` (like `X::IO`). -## In Perl6 exceptions are automatically 'thrown': -open 'foo'; #=> Failed to open file foo: no such file or directory -## It will also print out what line the error was thrown at -## and other error info. - -## You can throw an exception using `die`: -die 'Error!'; #=> Error! - -## Or more explicitly: -X::AdHoc.new(payload => 'Error!').throw; #=> Error! - -## In Perl 6, `orelse` is similar to the `or` operator, except it only matches -## undefined variables instead of anything evaluating as `False`. -## Undefined values include: `Nil`, `Mu` and `Failure` as well as `Int`, `Str` -## and other types that have not been initialized to any value yet. -## You can check if something is defined or not using the defined method: -my $uninitialized; -say $uninitiazilzed.defined; #=> False - -## When using `orelse` it will disarm the exception and alias $_ to that -## failure. This will prevent it to being automatically handled and printing -## lots of scary error messages to the screen. We can use the `exception` -## method on the `$_` variable to access the exception -open 'foo' orelse say "Something happened {.exception}"; - -## This also works: -open 'foo' orelse say "Something happened $_"; #=> Something happened - #=> Failed to open file foo: no such file or directory -## Both of those above work but in case we get an object from the left side -## that is not a failure we will probably get a warning. We see below how we -## can use try` and `CATCH` to be more specific with the exceptions we catch. -``` - -### Using `try` and `CATCH` - -```perl6 -## By using `try` and `CATCH` you can contain and handle exceptions without -## disrupting the rest of the program. The `try` block will set the last -## exception to the special variable `$!` (known as the error variable). -## Note: This has no relation to $!variables seen inside class definitions. - -try open 'foo'; -say "Well, I tried! $!" if defined $!; -#=> Well, I tried! Failed to open file foo: no such file or directory - -## Now, what if we want more control over handling the exception? -## Unlike many other languages, in Perl 6, you put the `CATCH` block *within* -## the block to `try`. Similar to how the `$_` variable was set when we -## 'disarmed' the exception with `orelse`, we also use `$_` in the CATCH block. -## Note: The `$!` variable is only set *after* the `try` block has caught an -## exception. By default, a `try` block has a `CATCH` block of its own that -## catches any exception (`CATCH { default {} }`). - -try { - my $a = (0 %% 0); - CATCH { - say "Something happened: $_" - } -} -#=> Something happened: Attempt to divide by zero using infix:<%%> - -## You can redefine it using `when`s (and `default`) to handle the exceptions -## you want to catch explicitly: - -try { - open 'foo'; - CATCH { - # In the `CATCH` block, the exception is set to the $_ variable. - when X::AdHoc { - say "Error: $_" - } - when X::Numeric::DivideByZero { - say "Error: $_"; - } - ## Any other exceptions will be re-raised, since we don't have a `default`. - ## Basically, if a `when` matches (or there's a `default`), the - ## exception is marked as "handled" so as to prevent its re-throw - ## from the `CATCH` block. You still can re-throw the exception (see below) - ## by hand. - } -} -#=>Error: Failed to open file /dir/foo: no such file or directory - -## There are also some subtleties to exceptions. Some Perl 6 subs return a -## `Failure`, which is a wrapper around an `Exception` object which is -## "unthrown". They're not thrown until you try to use the variables containing -## them unless you call `.Bool`/`.defined` on them - then they're handled. -## (the `.handled` method is `rw`, so you can mark it as `False` back yourself) -## You can throw a `Failure` using `fail`. Note that if the pragma `use fatal` -## is on, `fail` will throw an exception (like `die`). - -fail "foo"; # We're not trying to access the value, so no problem. -try { - fail "foo"; - CATCH { - default { - say "It threw because we tried to get the fail's value!" - } - } -} - -## There is also another kind of exception: Control exceptions. -## Those are "good" exceptions, which happen when you change your program's -## flow, using operators like `return`, `next` or `last`. -## You can "catch" those with `CONTROL` (not 100% working in Rakudo yet). -``` - -## Packages - -```perl6 -## Packages are a way to reuse code. Packages are like "namespaces", and any -## element of the six model (`module`, `role`, `class`, `grammar`, `subset` and -## `enum`) are actually packages. (Packages are the lowest common denominator) -## Packages are important - especially as Perl is well-known for CPAN, -## the Comprehensive Perl Archive Network. - -## You can use a module (bring its declarations into scope) with -## the `use` keyword: -use JSON::Tiny; # if you installed Rakudo* or Panda, you'll have this module -say from-json('[1]').perl; #=> [1] - -## You should not declare packages using the `package` keyword (unlike Perl 5). -## Instead, use `class Package::Name::Here;` to declare a class, or if you only -## want to export variables/subs, you can use `module` instead. - -module Hello::World { # bracketed form - # If `Hello` doesn't exist yet, it'll just be a "stub", - # that can be redeclared as something else later. - - # ... declarations here ... -} - -unit module Parse::Text; # file-scoped form which extends until - # the end of the file - -grammar Parse::Text::Grammar { - # A grammar is a package, which you could `use`. - # You will learn more about grammars in the regex section -} - -## As said before, any part of the six model is also a package. -## Since `JSON::Tiny` uses its own `JSON::Tiny::Actions` class, you can use it: -my $actions = JSON::Tiny::Actions.new; - -## We'll see how to export variables and subs in the next part. -``` - -## Declarators - -```perl6 -## In Perl 6, you get different behaviors based on how you declare a variable. -## You've already seen `my` and `has`, we'll now explore the others. - -## `our` - these declarations happen at `INIT` time -- (see "Phasers" below). -## It's like `my`, but it also creates a package variable. All packagish -## things such as `class`, `role`, etc. are `our` by default. - -module Var::Increment { - our $our-var = 1; # Note: `our`-declared variables cannot be typed. - my $my-var = 22; - - our sub Inc { - our sub available { # If you try to make inner `sub`s `our`... - # ... Better know what you're doing (Don't !). - say "Don't do that. Seriously. You'll get burned."; - } - - my sub unavailable { # `sub`s are `my`-declared by default - say "Can't access me from outside, I'm 'my'!"; - } - say ++$our-var; # Increment the package variable and output its value - } - -} - -say $Var::Increment::our-var; #=> 1, this works! -say $Var::Increment::my-var; #=> (Any), this will not work! - -Var::Increment::Inc; #=> 2 -Var::Increment::Inc; #=> 3 , notice how the value of $our-var was - # retained. -Var::Increment::unavailable; #=> Could not find symbol '&unavailable' - -## `constant` - these declarations happen at `BEGIN` time. You can use -## the `constant` keyword to declare a compile-time variable/symbol: -constant Pi = 3.14; -constant $var = 1; - -## And if you're wondering, yes, it can also contain infinite lists. -constant why-not = 5, 15 ... *; -say why-not[^5]; #=> 5 15 25 35 45 - -## `state` - these declarations happen at run time, but only once. State -## variables are only initialized one time. In other languages such as C -## they exist as `static` variables. -sub fixed-rand { - state $val = rand; - say $val; -} -fixed-rand for ^10; # will print the same number 10 times - -## Note, however, that they exist separately in different enclosing contexts. -## If you declare a function with a `state` within a loop, it'll re-create the -## variable for each iteration of the loop. See: -for ^5 -> $a { - sub foo { - state $val = rand; # This will be a different value for - # every value of `$a` - } - for ^5 -> $b { - say foo; # This will print the same value 5 times, - # but only 5. Next iteration will re-run `rand`. - } -} -``` - -## Phasers - -```perl6 -## Phasers in Perl 6 are blocks that happen at determined points of time in -## your program. They are called phasers because they mark a change in the -## phase of a program. For example, when the program is compiled, a for loop -## runs, you leave a block, or an exception gets thrown (The `CATCH` block is -## actually a phaser!). Some of them can be used for their return values, -## some of them can't (those that can have a "[*]" in the beginning of their -## explanation text). Let's have a look! - -## Compile-time phasers -BEGIN { say "[*] Runs at compile time, as soon as possible, only once" } -CHECK { say "[*] Runs at compile time, as late as possible, only once" } - -## Run-time phasers -INIT { say "[*] Runs at run time, as soon as possible, only once" } -END { say "Runs at run time, as late as possible, only once" } - -## Block phasers -ENTER { say "[*] Runs everytime you enter a block, repeats on loop blocks" } -LEAVE { - say "Runs everytime you leave a block, even when an exception - happened. Repeats on loop blocks." -} - -PRE { - say "Asserts a precondition at every block entry, - before ENTER (especially useful for loops)"; - say "If this block doesn't return a truthy value, - an exception of type X::Phaser::PrePost is thrown."; -} - -## Example: -for 0..2 { - PRE { $_ > 1 } # This is going to blow up with "Precondition failed" -} - -POST { - say "Asserts a postcondition at every block exit, - after LEAVE (especially useful for loops)"; - say "If this block doesn't return a truthy value, - an exception of type X::Phaser::PrePost is thrown, like PRE."; -} - -for 0..2 { - POST { $_ < 2 } # This is going to blow up with "Postcondition failed" -} - -## Block/exceptions phasers -sub { - KEEP { say "Runs when you exit a block successfully - (without throwing an exception)" } - UNDO { say "Runs when you exit a block unsuccessfully - (by throwing an exception)" } -} - -## Loop phasers -for ^5 { - FIRST { say "[*] The first time the loop is run, before ENTER" } - NEXT { say "At loop continuation time, before LEAVE" } - LAST { say "At loop termination time, after LEAVE" } -} - -## Role/class phasers -COMPOSE { "When a role is composed into a class. /!\ NOT YET IMPLEMENTED" } - -## They allow for cute tricks or clever code...: -say "This code took " ~ (time - CHECK time) ~ "s to compile"; - -## ... or clever organization: -sub do-db-stuff { - $db.start-transaction; # start a new transaction - KEEP $db.commit; # commit the transaction if all went well - UNDO $db.rollback; # or rollback if all hell broke loose -} -``` - -## Statement prefixes - -```perl6 -## Those act a bit like phasers: they affect the behavior of the following -## code. Though, they run in-line with the executable code, so they're in -## lowercase. (`try` and `start` are theoretically in that list, but explained -## elsewhere) Note: all of these (except start) don't need explicit curly -## braces `{` and `}`. - -## `do` - (which you already saw) runs a block or a statement as a term. -## Normally you cannot use a statement as a value (or "term"). `do` helps us -## do it. - -# my $value = if True { 1 } # this fails since `if` is a statement -my $a = do if True { 5 } # with `do`, `if` is now a term returning a value - -## `once` - makes sure a piece of code only runs once. -for ^5 { - once say 1 -}; #=> 1, only prints ... once - -## Similar to `state`, they're cloned per-scope. -for ^5 { - sub { once say 1 }() -}; #=> 1 1 1 1 1, prints once per lexical scope. - -## `gather` - co-routine thread. The `gather` constructs allows us to `take` -## several values from an array/list, much like `do`. -say gather for ^5 { - take $_ * 3 - 1; - take $_ * 3 + 1; -} -#=> -1 1 2 4 5 7 8 10 11 13 - -say join ',', gather if False { - take 1; - take 2; - take 3; -} -# Doesn't print anything. - -## `eager` - evaluates a statement eagerly (forces eager context) -## Don't try this at home: -# eager 1..*; # this will probably hang for a while (and might crash ...). -## But consider: -constant thrice = gather for ^3 { say take $_ }; # Doesn't print anything -## versus: -constant thrice = eager gather for ^3 { say take $_ }; #=> 0 1 2 -``` - -## Iterables - -```perl6 -## Iterables are objects that can be iterated over which are -## are similar to the `for` construct. - -## `flat` - flattens iterables. -say (1, 10, (20, 10) ); #=> (1 10 (20 10)), notice how neste lists are - # preserved -say (1, 10, (20, 10) ).flat; #=> (1 10 20 10), now the iterable is flat - -## - `lazy` - defers actual evaluation until value is fetched by forcing -## lazy context. -my @lazy-array = (1..100).lazy; -say @lazy-array.is-lazy; #=> True, check for laziness with the `is-lazy` method. -say @lazy-array; #=> [...] List has not been iterated on! -my @lazy-array { .print }; # This works and will only do as much work as - # is needed. - -# ( **TODO** explain that gather/take and map are all lazy) - -## `sink` - an `eager` that discards the results by forcing sink context. -constant nilthingie = sink for ^3 { .say } #=> 0 1 2 -say nilthingie.perl; #=> Nil - -## `quietly` - suppresses warnings in blocks. -quietly { warn 'This is a warning!' }; #=> No output - -## `contend` - attempts side effects under STM -## Not yet implemented! -``` - -## More operators thingies! - -```perl6 -## Everybody loves operators! Let's get more of them. - -## The precedence list can be found here: -## https://docs.perl6.org/language/operators#Operator_Precedence -## But first, we need a little explanation about associativity: - -## Binary operators: -$a ! $b ! $c; # with a left-associative `!`, this is `($a ! $b) ! $c` -$a ! $b ! $c; # with a right-associative `!`, this is `$a ! ($b ! $c)` -$a ! $b ! $c; # with a non-associative `!`, this is illegal -$a ! $b ! $c; # with a chain-associative `!`, this is `($a ! $b) and ($b ! $c)` -$a ! $b ! $c; # with a list-associative `!`, this is `infix:<>` - -## Unary operators: -!$a! # with left-associative `!`, this is `(!$a)!` -!$a! # with right-associative `!`, this is `!($a!)` -!$a! # with non-associative `!`, this is illegal -``` - -### Create your own operators! - -```perl6 -## Okay, you've been reading all of that, so you might want to try something -## more exciting?! I'll tell you a little secret (or not-so-secret): -## In Perl 6, all operators are actually just funny-looking subroutines. - -## You can declare an operator just like you declare a sub: -# prefix refers to the operator categories (prefix, infix, postfix, etc). -sub prefix:( $winner ) { - say "$winner Won!"; -} -win "The King"; #=> The King Won! - # (prefix means 'before') - -## you can still call the sub with its "full name": -say prefix:(True); #=> False -prefix:("The Queen"); #=> The Queen Won! - -sub postfix:( Int $n ) { - [*] 2..$n; # using the reduce meta-operator... See below ;-)! -} -say 5!; #=> 120 - # Postfix operators ('after') have to come *directly* after the term. - # No whitespace. You can use parentheses to disambiguate, i.e. `(5!)!` - -sub infix:( Int $n, Block $r ) { # infix ('between') - for ^$n { - $r(); # You need the explicit parentheses to call the function in `$r`, - # else you'd be referring at the variable itself, like with `&r`. - } -} -3 times -> { say "hello" }; #=> hello - #=> hello - #=> hello -## It's recommended to put spaces around your -## infix operator calls. - -## For circumfix and post-circumfix ones -sub circumfix:<[ ]>( Int $n ) { - $n ** $n -} -say [5]; #=> 3125 - # circumfix means 'around'. Again, no whitespace. - -sub postcircumfix:<{ }>( Str $s, Int $idx ) { - ## post-circumfix is 'after a term, around something' - $s.substr($idx, 1); -} -say "abc"{1}; #=> b - # after the term `"abc"`, and around the index (1) - -## This really means a lot -- because everything in Perl 6 uses this. -## For example, to delete a key from a hash, you use the `:delete` adverb -## (a simple named argument underneath): -%h{$key}:delete; -## equivalent to: -postcircumfix:<{ }>( %h, $key, :delete ); # (you can call operators like this) - -## It's *all* using the same building blocks! Syntactic categories -## (prefix infix ...), named arguments (adverbs), ..., etc. used to build -## the language - are available to you. Obviously, you're advised against -## making an operator out of *everything* -- with great power comes great -## responsibility. -``` - -### Meta operators! - -```perl6 -## Oh boy, get ready!. Get ready, because we're delving deep into the rabbit's -## hole, and you probably won't want to go back to other languages after -## reading this. (I'm guessing you don't want to go back at this point but -## let's continue, for the journey is long and enjoyable!). - -## Meta-operators, as their name suggests, are *composed* operators. -## Basically, they're operators that act on another operators. - -## The reduce meta-operator is a prefix meta-operator that takes a binary -## function and one or many lists. If it doesn't get passed any argument, -## it either returns a "default value" for this operator (a meaningless value) -## or `Any` if there's none (examples below). Otherwise, it pops an element -## from the list(s) one at a time, and applies the binary function to the last -## result (or the list's first element) and the popped element. - -## To sum a list, you could use the reduce meta-operator with `+`, i.e.: -say [+] 1, 2, 3; #=> 6, equivalent to (1+2)+3. - -## To multiply a list -say [*] 1..5; #=> 120, equivalent to ((((1*2)*3)*4)*5). - -## You can reduce with any operator, not just with mathematical ones. -## For example, you could reduce with `//` to get first defined element -## of a list: -say [//] Nil, Any, False, 1, 5; #=> False - # (Falsey, but still defined) -## Or with relational operators, i.e., `>` to check elements of a list -## are ordered accordingly: -say say [>] 234, 156, 6, 3, -20; #=> True - -## Default value examples: -say [*] (); #=> 1 -say [+] (); #=> 0 - # meaningless values, since N*1=N and N+0=N. -say [//]; #=> (Any) - # There's no "default value" for `//`. - -## You can also call it with a function you made up, using double brackets: -sub add($a, $b) { $a + $b } -say [[&add]] 1, 2, 3; #=> 6 - -## The zip meta-operator is an infix meta-operator that also can be used as a -## "normal" operator. It takes an optional binary function (by default, it -## just creates a pair), and will pop one value off of each array and call -## its binary function on these until it runs out of elements. It returns an -## array with all of these new elements. -say (1, 2) Z (3, 4); #=> ((1, 3), (2, 4)), since by default the function - # makes an array. -say 1..3 Z+ 4..6; #=> (5, 7, 9), using the custom infix:<+> function - -## Since `Z` is list-associative (see the list above), -## you can use it on more than one list -(True, False) Z|| (False, False) Z|| (False, False); # (True, False) - -## And, as it turns out, you can also use the reduce meta-operator with it: -[Z||] (True, False), (False, False), (False, False); # (True, False) - - -## And to end the operator list: - -## The sequence operator is one of Perl 6's most powerful features: -## it's composed of first, on the left, the list you want Perl 6 to deduce from -## (and might include a closure), and on the right, a value or the predicate -## that says when to stop (or a Whatever Star for a lazy infinite list). - -my @list = 1, 2, 3...10; # basic arithmetic sequence -# my @list = 1, 3, 6...10; # this dies because Perl 6 can't figure out the end -my @list = 1, 2, 3...^10; # as with ranges, you can exclude the last element - # (the iteration ends when the predicate matches). -my @list = 1, 3, 9...* > 30; # you can use a predicate (with the Whatever Star). -my @list = 1, 3, 9 ... { $_ > 30 }; # (equivalent to the above - # using a block here). - -my @fib = 1, 1, *+* ... *; # lazy infinite list of fibonacci sequence, - # computed using a closure! -my @fib = 1, 1, -> $a, $b { $a + $b } ... *; # (equivalent to the above) -my @fib = 1, 1, { $^a + $^b } ... *; # (also equivalent to the above) -## $a and $b will always take the previous values, meaning here -## they'll start with $a = 1 and $b = 1 (values we set by hand), -## then $a = 1 and $b = 2 (result from previous $a+$b), and so on. - -say @fib[^10]; #=> 1 1 2 3 5 8 13 21 34 55 - # (using a range as the index) -## Note: as for ranges, once reified, elements aren't re-calculated. -## That's why `@primes[^100]` will take a long time the first time you print -## it, then will be instateneous. -``` - -## Regular Expressions - -```perl6 -## I'm sure a lot of you have been waiting for this one. Well, now that you know -## a good deal of Perl 6 already, we can get started. First off, you'll have to -## forget about "PCRE regexps" (perl-compatible regexps). -## -## IMPORTANT: Don't skip them because you know PCRE. They're different. Some -## things are the same (like `?`, `+`, and `*`), but sometimes the semantics -## change (`|`). Make sure you read carefully, because you might trip over a -## new behavior. -## -## Perl 6 has many features related to RegExps. After all, Rakudo parses itself. -## We're first going to look at the syntax itself, then talk about grammars -## (PEG-like), differences between `token`, `regex` and `rule` declarators, -## and some more. Side note: you still have access to PCRE regexps using the -## `:P5` modifier which we won't be discussing this in this tutorial, though. -## -## In essence, Perl 6 natively implements PEG ("Parsing Expression Grammars"). -## The pecking order for ambiguous parses is determined by a multi-level -## tie-breaking test: -## - Longest token matching: `foo\s+` beats `foo` (by 2 or more positions) -## - Longest literal prefix: `food\w*` beats `foo\w*` (by 1) -## - Declaration from most-derived to less derived grammars -## (grammars are actually classes) -## - Earliest declaration wins -say so 'a' ~~ /a/; #=> True -say so 'a' ~~ / a /; #=> True, more readable with some spaces! - -## In all our examples, we're going to use the smart-matching operator against -## a regexp. We're converting the result using `so` to a Boolean value because, -## in fact, it's returning a `Match` object. They know how to respond to list -## indexing, hash indexing, and return the matched string. The results of the -## match are available in the `$/` variable (implicitly lexically-scoped). You -## can also use the capture variables which start at 0: `$0`, `$1', `$2`... -## -## You can also note that `~~` does not perform start/end checking, meaning -## the regexp can be matched with just one character of the string. We'll -## explain later how you can do it. - -## In Perl 6, you can have any alphanumeric as a literal, everything else has -## to be escaped by using a backslash or quotes. -say so 'a|b' ~~ / a '|' b /; #=> `True`, it wouldn't mean the same thing if - # `|` wasn't escaped. -say so 'a|b' ~~ / a \| b /; #=> `True`, another way to escape it. - -## The whitespace in a regexp is actually not significant, unless you use the -## `:s` (`:sigspace`, significant space) adverb. -say so 'a b c' ~~ / a b c /; #=> `False`, space is not significant here! -say so 'a b c' ~~ /:s a b c /; #=> `True`, we added the modifier `:s` here. - -## If we use only one space between strings in a regex, Perl 6 will warn us: -say so 'a b c' ~~ / a b c /; #=> `False`, with warning about space -say so 'a b c' ~~ / a b c /; #=> `False` - -## Please use quotes or :s (:sigspace) modifier (or, to suppress this warning, -## omit the space, or otherwise change the spacing). To fix this and make the -## spaces less ambiguous, either use at least two spaces between strings -## or use the `:s` adverb. - -## As we saw before, we can embed the `:s` inside the slash delimiters, but we -## can also put it outside of them if we specify `m` for 'match': -say so 'a b c' ~~ m:s/a b c/; #=> `True` - -## By using `m` to specify 'match', we can also use delimiters other than -## slashes: -say so 'abc' ~~ m{a b c}; #=> `True` -say so 'abc' ~~ m[a b c]; #=> `True` -# m/.../ is equivalent to /.../ - -## Use the :i adverb to specify case insensitivity: -say so 'ABC' ~~ m:i{a b c}; #=> `True` - -## However, whitespace is important as for how modifiers are applied ( -## (which you'll see just below) ... - -## Quantifying - `?`, `+`, `*` and `**`. -## `?` - zero or one match -so 'ac' ~~ / a b c /; #=> `False` -so 'ac' ~~ / a b? c /; #=> `True`, the "b" matched 0 times. -so 'abc' ~~ / a b? c /; #=> `True`, the "b" matched 1 time. - -## ...As you read before, whitespace is important because it determines which -## part of the regexp is the target of the modifier: -so 'def' ~~ / a b c? /; #=> `False`, only the `c` is optional -so 'def' ~~ / a b? c /; #=> `False`, whitespace is not significant -so 'def' ~~ / 'abc'? /; #=> `True`, the whole "abc" group is optional - -## Here (and below) the quantifier applies only to the `b` - -## `+` - one or more matches -so 'ac' ~~ / a b+ c /; #=> `False`, `+` wants at least one matching -so 'abc' ~~ / a b+ c /; #=> `True`, one is enough -so 'abbbbc' ~~ / a b+ c /; #=> `True`, matched 4 "b"s - -## `*` - zero or more matches -so 'ac' ~~ / a b* c /; #=> `True`, they're all optional. -so 'abc' ~~ / a b* c /; #=> `True` -so 'abbbbc' ~~ / a b* c /; #=> `True` -so 'aec' ~~ / a b* c /; #=> `False`. "b"(s) are optional, not replaceable. - -## `**` - (Unbound) Quantifier -## If you squint hard enough, you might understand why exponentation is used -## for quantity. -so 'abc' ~~ / a b**1 c /; #=> `True`, (exactly one time) -so 'abc' ~~ / a b**1..3 c /; #=> `True`, (one to three times) -so 'abbbc' ~~ / a b**1..3 c /; #=> `True` -so 'abbbbbbc' ~~ / a b**1..3 c /; #=> `False, (too much) -so 'abbbbbbc' ~~ / a b**3..* c /; #=> `True`, (infinite ranges are okay) - -## `<[]>` - Character classes -## Character classes are the equivalent of PCRE's `[]` classes, but they use a -## more perl6-ish syntax: -say 'fooa' ~~ / f <[ o a ]>+ /; #=> 'fooa' - -## You can use ranges: -say 'aeiou' ~~ / a <[ e..w ]> /; #=> 'ae' - -## Just like in normal regexes, if you want to use a special character, escape -## it (the last one is escaping a space which would be equivalent to using -## ' '): -say 'he-he !' ~~ / 'he-' <[ a..z \! \ ]> + /; #=> 'he-he !' - -## You'll get a warning if you put duplicate names (which has the nice effect -## of catching the raw quoting): -'he he' ~~ / <[ h e ' ' ]> /; -# Warns "Repeated character (') unexpectedly found in character class" - -## You can also negate character classes... (`<-[]>` equivalent to `[^]` in PCRE) -so 'foo' ~~ / <-[ f o ]> + /; #=> False - -## ... and compose them: -so 'foo' ~~ / <[ a..z ] - [ f o ]> + /; #=> `False`, (any letter except f and o) -so 'foo' ~~ / <-[ a..z ] + [ f o ]> + /; #=> `True`, (no letter except f and o) -so 'foo!' ~~ / <-[ a..z ] + [ f o ]> + /; #=> `True`, (the + doesn't replace the - # left part) -``` - -### Grouping and capturing - -```perl6 -## Group: you can group parts of your regexp with `[]`. Unlike PCRE's `(?:)`, -## these groups are *not* captured. -so 'abc' ~~ / a [ b ] c /; # `True`. The grouping does pretty much nothing -so 'foo012012bar' ~~ / foo [ '01' <[0..9]> ] + bar /; - -## The previous line returns `True`. The regex matches "012" 1 or more time -## (achieved by the the `+` applied to the group). - -## But this does not go far enough, because we can't actually get back what -## we matched. - -## Capture: The results of a regexp can be *captured* by using parentheses. -so 'fooABCABCbar' ~~ / foo ( 'A' <[A..Z]> 'C' ) + bar /; # `True`. (using `so` - # here, `$/` below) - -## So, starting with the grouping explanations. -## As we said before, our `Match` object is stored inside the `$/` variable: -say $/; # Will either print some weird stuff or `Nil` if nothing matched. - -## As we also said before, it has array indexing: -say $/[0]; #=> ｢ABC｣ ｢ABC｣ - # These corner brackets are `Match` objects. - # Here, we have an array of these. -say $0; # The same as above. - -## Our capture is `$0` because it's the first and only one capture in the -## regexp. You might be wondering why it's an array, and the answer is simple: -## Some captures (indexed using `$0`, `$/[0]` or a named one) will be an array -## if and only if they can have more than one element. Thus any capture with -## `*`, `+` and `**` (whatever the operands), but not with `?`. -## Let's use examples to see that: - -## Note: We quoted A B C to demonstrate that the whitespace between them isn't -## significant. If we want the whitespace to *be* significant there, we -## can use the :sigspace modifier. -say so 'fooABCbar' ~~ / foo ( "A" "B" "C" )? bar /; #=> `True` -say $/[0]; #=> ｢ABC｣ -say $0.WHAT; #=> (Match) - # There can't be more than one, so it's only a single match object. -say so 'foobar' ~~ / foo ( "A" "B" "C" )? bar /; #=> True -say $0.WHAT; #=> (Any) - # This capture did not match, so it's empty -so 'foobar' ~~ / foo ( "A" "B" "C" ) ** 0..1 bar /; #=> `True` -say $0.WHAT; #=> (Array) - # A specific quantifier will always capture an Array, - # be a range or a specific value (even 1). - -## The captures are indexed per nesting. This means a group in a group will be -## nested under its parent group: `$/[0][0]`, for this code: -'hello-~-world' ~~ / ( 'hello' ( <[ \- \~ ]> + ) ) 'world' /; -say $/[0].Str; #=> hello~ -say $/[0][0].Str; #=> ~ - -## This stems from a very simple fact: `$/` does not contain strings, integers -## or arrays, it only contains Match objects. These contain the `.list`, `.hash` -## and `.Str` methods but you can also just use `match` for hash access -## and `match[idx]` for array access. -say $/[0].list.perl; #=> (Match.new(...),).list - # We can see it's a list of Match objects. These contain - # a bunch of info: where the match started/ended, - # the "ast" (see actions later), etc. - # You'll see named capture below with grammars. - -## Alternation - the `or` of regexps -## WARNING: They are DIFFERENT from PCRE regexps. -say so 'abc' ~~ / a [ b | y ] c /; #=> `True`. Either "b" or "y". -say so 'ayc' ~~ / a [ b | y ] c /; #=> `True`. Obviously enough... - -## The difference between this `|` and the one you're used to is -## LTM ("Longest Token Matching"). This means that the engine will always -## try to match as much as possible in the string. -say 'foo' ~~ / fo | foo /; #=> `foo`, instead of `fo`, because it's longer. - -## To decide which part is the "longest", it first splits the regex in -## two parts: -## The "declarative prefix" (the part that can be statically analyzed) -## and the procedural parts: -## - The declarative prefixes include alternations (`|`), conjunctions (`&`), -## sub-rule calls (not yet introduced), literals, characters classes and -## quantifiers. -## - The procedural part include everything else: back-references, -## code assertions, and other things that can't traditionnaly be represented -## by normal regexps. -## -## Then, all the alternatives are tried at once, and the longest wins. -## Examples: -## DECLARATIVE | PROCEDURAL -/ 'foo' \d+ [ || ] /; -## DECLARATIVE (nested groups are not a problem) -/ \s* [ \w & b ] [ c | d ] /; -## However, closures and recursion (of named regexps) are procedural. -## There are also more complicated rules, like specificity (literals win over -## character classes). - -## Note: the first-matching `or` still exists, but is now spelled `||` -say 'foo' ~~ / fo || foo /; #=> `fo` now. -``` - -## Extra: the MAIN subroutine - -```perl6 -## The `MAIN` subroutine is called when you run a Perl 6 file directly. It's -## very powerful, because Perl 6 actually parses the arguments and pass them -## as such to the sub. It also handles named argument (`--foo`) and will even -## go as far as to autogenerate a `--help` flag. -sub MAIN($name) { - say "Hello, $name!"; -} -## This produces: -## $ perl6 cli.pl -## Usage: -## t.pl - -## And since it's a regular Perl 6 sub, you can have multi-dispatch: -## (using a "Bool" for the named argument so that we can do `--replace` -## instead of `--replace=1`. The presence of `--replace` indicates truthness -## while its absence falseness). - -subset File of Str where *.IO.d; # convert to IO object to check the file exists - -multi MAIN('add', $key, $value, Bool :$replace) { ... } -multi MAIN('remove', $key) { ... } -multi MAIN('import', File, Str :$as) { ... } # omitting parameter name - -## This produces: -## $ perl6 cli.pl -## Usage: -## cli.p6 [--replace] add -## cli.p6 remove -## cli.p6 [--as=] import - -## As you can see, this is *very* powerful. It even went as far as to show inline -## the constants (the type is only displayed if the argument is `$`/is named). -``` - -## APPENDIX A: -### List of things - -```perl6 -## It's assumed by now you know the Perl6 basics. This section is just here to -## list some common operations, but which are not in the "main part" of the -## tutorial to avoid bloating it up. - -## Operators - -## Sort comparison - they return one value of the `Order` enum: `Less`, `Same` -## and `More` (which numerify to -1, 0 or +1 respectively). -1 <=> 4; # sort comparison for numerics -'a' leg 'b'; # sort comparison for string -$obj eqv $obj2; # sort comparison using eqv semantics - -## Generic ordering -3 before 4; # True -'b' after 'a'; # True - -## Short-circuit default operator - similar to `or` and `||`, but instead -## returns the first *defined* value: -say Any // Nil // 0 // 5; #=> 0 - -## Short-circuit exclusive or (XOR) - returns `True` if one (and only one) of -## its arguments is true -say True ^^ False; #=> True - -## Flip flops - these operators (`ff` and `fff`, equivalent to P5's `..` -## and `...`) are operators that take two predicates to test: They are `False` -## until their left side returns `True`, then are `True` until their right -## side returns `True`. Similar to ranges, you can exclude the iteration when -## it become `True`/`False` by using `^` on either side. Let's start with an -## example : -for { - # by default, `ff`/`fff` smart-match (`~~`) against `$_`: - if 'met' ^ff 'meet' { # Won't enter the if for "met" - .say # (explained in details below). - } - - if rand == 0 ff rand == 1 { # compare variables other than `$_` - say "This ... probably will never run ..."; - } -} - -## This will print "young hero we shall meet" (excluding "met"): the flip-flop -## will start returning `True` when it first encounters "met" (but will still -## return `False` for "met" itself, due to the leading `^` on `ff`), until it -## sees "meet", which is when it'll start returning `False`. - -## The difference between `ff` (awk-style) and `fff` (sed-style) is that `ff` -## will test its right side right when its left side changes to `True`, and can -## get back to `False` right away (*except* it'll be `True` for the iteration -## that matched) while `fff` will wait for the next iteration to try its right -## side, once its left side changed: -.say if 'B' ff 'B' for ; #=> B B - # because the right-hand-side was tested - # directly (and returned `True`). - # "B"s are printed since it matched that - # time (it just went back to `False` - # right away). -.say if 'B' fff 'B' for ; #=> B C B - # The right-hand-side wasn't tested until - # `$_` became "C" - # (and thus did not match instantly). - -## A flip-flop can change state as many times as needed: -for { - .say if $_ eq 'start' ^ff^ $_ eq 'stop'; # exclude both "start" and "stop", - #=> "print it print again" -} - -## You might also use a Whatever Star, which is equivalent to `True` for the -## left side or `False` for the right: -for (1, 3, 60, 3, 40, 60) { # Note: the parenthesis are superfluous here - # (sometimes called "superstitious parentheses") - .say if $_ > 50 ff *; # Once the flip-flop reaches a number greater - # than 50, it'll never go back to `False` - #=> 60 3 40 60 -} - -## You can also use this property to create an `if` that'll not go through the -## first time: -for { - .say if * ^ff *; # the flip-flop is `True` and never goes back to `False`, - # but the `^` makes it *not run* on the first iteration - #=> b c -} - -## The `===` operator is the value identity operator and uses `.WHICH` on the -## objects to compare them while `=:=` is the container identity operator -## and uses `VAR()` on the objects to compare them. -``` - -If you want to go further, you can: - - - Read the [Perl 6 Docs](https://docs.perl6.org/). This is a great - resource on Perl6. If you are looking for something, use the search bar. - This will give you a dropdown menu of all the pages referencing your search - term (Much better than using Google to find Perl 6 documents!). - - Read the [Perl 6 Advent Calendar](http://perl6advent.wordpress.com/). This - is a great source of Perl 6 snippets and explanations. If the docs don't - describe something well enough, you may find more detailed information here. - This information may be a bit older but there are many great examples and - explanations. Posts stopped at the end of 2015 when the language was declared - stable and Perl 6.c was released. - - Come along on `#perl6` at `irc.freenode.net`. The folks here are - always helpful. - - Check the [source of Perl 6's functions and - classes](https://github.com/rakudo/rakudo/tree/nom/src/core). Rakudo is - mainly written in Perl 6 (with a lot of NQP, "Not Quite Perl", a Perl 6 subset - easier to implement and optimize). - - Read [the language design documents](http://design.perl6.org). They explain - P6 from an implementor point-of-view, but it's still very interesting. -- cgit v1.2.3