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