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Diffstat (limited to 'perl6.html.markdown')
| -rw-r--r-- | perl6.html.markdown | 178 |
1 files changed, 92 insertions, 86 deletions
diff --git a/perl6.html.markdown b/perl6.html.markdown index 3bb87916..1829f964 100644 --- a/perl6.html.markdown +++ b/perl6.html.markdown @@ -1,16 +1,16 @@ --- -name: perl6 category: language language: perl6 filename: learnperl6.pl contributors: - - ["Nami-Doc", "http://github.com/Nami-Doc"] + - ["vendethiel", "http://github.com/vendethiel"] --- -Perl 6 is a highly capable, feature-rich programming language made for the -upcoming hundred years. +Perl 6 is a highly capable, feature-rich programming language made for at +least the next hundred years. -Perl 6 runs on [the MoarVM](http://moarvm.com) and the JVM. +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. @@ -72,7 +72,7 @@ say @array; #=> a 6 b # except they get "flattened" (hash context), removing duplicated keys. my %hash = 1 => 2, 3 => 4; -my %hash = autoquoted => "key", # keys get auto-quoted +my %hash = foo => "bar", # keys get auto-quoted "some other" => "value", # trailing commas are okay ; my %hash = <key1 value1 key2 value2>; # you can also create a hash @@ -93,7 +93,6 @@ say %hash<key2>; # If it's a string, you can actually use <> # (`{key1}` doesn't work, as Perl6 doesn't have barewords) ## * Subs (subroutines, or functions in most other languages). -# Stored in variable, they use `&`. sub say-hello { say "Hello, world" } sub say-hello-to(Str $name) { # You can provide the type of an argument @@ -104,8 +103,8 @@ sub say-hello-to(Str $name) { # You can provide the type of an argument ## It can also have optional arguments: sub with-optional($arg?) { # the "?" marks the argument optional - say "I might return `(Any)` if I don't have an argument passed, - or I'll return my argument"; + say "I might return `(Any)` (Perl's "null"-like value) if I don't have + an argument passed, or I'll return my argument"; $arg; } with-optional; # returns Any @@ -122,14 +121,14 @@ hello-to('You'); #=> Hello, You ! ## You can also, by using a syntax akin to the one of hashes (yay unified syntax !), ## pass *named* arguments to a `sub`. -# They're optional, and will default to "Any" (Perl's "null"-like value). +# They're optional, and will default to "Any". sub with-named($normal-arg, :$named) { say $normal-arg + $named; } with-named(1, named => 6); #=> 7 # There's one gotcha to be aware of, here: # If you quote your key, Perl 6 won't be able to see it at compile time, -# and you'll have a single Pair object as a positional paramater, +# and you'll have a single Pair object as a positional parameter, # which means this fails: with-named(1, 'named' => 6); @@ -140,7 +139,7 @@ sub with-mandatory-named(:$str!) { say "$str !"; } with-mandatory-named(str => "My String"); #=> My String ! -with-mandatory-named; # run time error: "Required named parameter not passed" +with-mandatory-named; # run time error: "Required named parameter not passed" with-mandatory-named(3); # run time error: "Too many positional parameters passed" ## If a sub takes a named boolean argument ... @@ -159,7 +158,7 @@ named-def; #=> 5 named-def(def => 15); #=> 15 # Since you can omit parenthesis to call a function with no arguments, -# you need "&" in the name to capture `say-hello`. +# you need "&" in the name to store `say-hello` in a variable. my &s = &say-hello; my &other-s = sub { say "Anonymous function !" } @@ -170,8 +169,8 @@ sub as-many($head, *@rest) { # `*@` (slurpy) will basically "take everything els say @rest.join(' / ') ~ " !"; } say as-many('Happy', 'Happy', 'Birthday'); #=> Happy / Birthday ! - # Note that the splat did not consume - # the parameter before. + # Note that the splat (the *) did not + # consume the parameter before. ## You can call a function with an array using the # "argument list flattening" operator `|` @@ -194,7 +193,7 @@ sub mutate($n is rw) { say "\$n is now $n !"; } -# If what you want is 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: my $x = 42; @@ -210,7 +209,7 @@ say $x; #=> 52 # - `if` # Before talking about `if`, we need to know which values are "Truthy" # (represent True), and which are "Falsey" (or "Falsy") -- represent False. -# Only these values are Falsey: (), 0, "", Nil, A type (like `Str` or `Int`), +# 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 { @@ -231,7 +230,7 @@ say "Quite truthy" if True; # - Ternary conditional, "?? !!" (like `x ? y : z` in some other languages) my $a = $condition ?? $value-if-true !! $value-if-false; -# - `given`-`when` looks like other languages `switch`, but much more +# - `given`-`when` looks like other languages' `switch`, but much more # powerful thanks to smart matching and thanks to Perl 6's "topic variable", $_. # # This variable contains the default argument of a block, @@ -287,7 +286,7 @@ for @array -> $variable { # That means you can use `when` in a `for` just like you were in a `given`. for @array { say "I've got $_"; - + .say; # This is also allowed. # A dot call with no "topic" (receiver) is sent to `$_` by default $_.say; # the above and this are equivalent. @@ -374,10 +373,14 @@ say @array[^10]; # you can pass arrays as subscripts and it'll return say join(' ', @array[15..*]); #=> 15 16 17 18 19 # which is equivalent to: say join(' ', @array[-> $n { 15..$n }]); +# Note: if you try to do either of those with an infinite array, +# you'll trigger an infinite loop (your program won't finish) + +# You can use that in most places you'd expect, even assigning to an array +my @numbers = ^20; -# You can use that in most places you'd expect, even assigning to an array -my @numbers = ^20; -my @seq = 3, 9 ... * > 95; # 3 9 15 21 27 [...] 81 87 93 99 +# 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. say @numbers; #=> 0 1 2 3 4 3 9 15 21 [...] 81 87 @@ -522,7 +525,7 @@ map(sub ($a, $b) { $a + $b + 3 }, @array); # (here with `sub`) # The constructs for declaring types are "class", "role", # which you'll see later. -# For now, let us examinate "subset": +# 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), @@ -605,40 +608,39 @@ sub foo { bar(); # call `bar` in-place } sub bar { - say $*foo; # `$*a` will be looked in the call stack, and find `foo`'s, + say $*foo; # `$*foo` will be looked in the call stack, and find `foo`'s, # even though the blocks aren't nested (they're call-nested). #=> 1 } ### Object Model -## Perl 6 has a quite comprehensive object model # You declare a class with the keyword `class`, fields with `has`, -# methods with `method`. Every field to private, and is named `$!attr`, -# but you have `$.` to get a public (immutable) accessor along with it. -# (using `$.` is like using `$!` plus a `method` with the same name) +# methods with `method`. Every attribute that is private is named `$!attr`. +# Immutable public attributes are named `$.attr` +# (you can make them mutable with `is rw`) -# (Perl 6's object model ("SixModel") is very flexible, +# Perl 6's object model ("SixModel") is very flexible, # and allows you to dynamically add methods, change semantics, etc ... # (this will not be covered here, and you should refer to the Synopsis). class A { has $.field; # `$.field` is immutable. # From inside the class, use `$!field` to modify it. - has $.other-field is rw; # You can obviously mark a public field `rw`. + has $.other-field is rw; # You can mark a public attribute `rw`. has Int $!private-field = 10; method get-value { $.field + $!private-field; } - + method set-value($n) { # $.field = $n; # As stated before, you can't use the `$.` immutable version. $!field = $n; # This works, because `$!` is always mutable. - + $.other-field = 5; # This works, because `$.other-field` is `rw`. } - + method !private-method { say "This method is private to the class !"; } @@ -653,23 +655,22 @@ $a.other-field = 10; # This, however, works, because the public field # is mutable (`rw`). ## Perl 6 also has inheritance (along with multiple inheritance) -# (though considered a misfeature by many) class A { has $.val; - + submethod not-inherited { say "This method won't be available on B."; say "This is most useful for BUILD, which we'll see later"; } - + method bar { $.val * 5 } } class B is A { # inheritance uses `is` method foo { say $.val; } - + method bar { $.val * 10 } # this shadows A's `bar` } @@ -696,20 +697,20 @@ role PrintableVal { # 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 fields are put together, which means a class can access # the private fields/methods of its roles (but not the inverse !): method access { say $!counter++; } - + # However, this: # method print {} # is ONLY valid when `print` isn't a `multi` with the same dispatch. # (this means a parent class can shadow a child class's `multi print() {}`, # but it's an error if a role does) - + # NOTE: You can use a role as a class (with `is ROLE`). In this case, methods # will be shadowed, since the compiler will consider `ROLE` to be a class. } @@ -735,7 +736,7 @@ try { # You can throw an exception using `die`: die X::AdHoc.new(payload => 'Error !'); -# You can access the last exception with `$!` (usually used in a `CATCH` block) +# You can access the last exception with `$!` (use `$_` in a `CATCH` block) # There are also some subtelties 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 @@ -748,7 +749,7 @@ fail "foo"; # We're not trying to access the value, so no problem. try { fail "foo"; CATCH { - default { say "It threw because we try to get the fail's value!" } + default { say "It threw because we tried to get the fail's value!" } } } @@ -760,25 +761,21 @@ try { ### Packages # 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 denomitor) +# 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 usually don't use packages directly: you use `class Package::Name::Here;`, -# or if you only want to export variables/subs, you can use `module`: +# You're not supposed to use the package keyword, usually: +# you 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", # that can be redeclared as something else later. # ... declarations here ... } -module Parse::Text; # file-scoped form +unit module Parse::Text; # file-scoped form grammar Parse::Text::Grammar { # A grammar is a package, which you could `use` } -# NOTE for Perl 5 users: even though the `package` keyword exists, -# the braceless form is invalid (to catch a "perl5ism"). This will error out: -# package Foo; # because Perl 6 will think the entire file is Perl 5 -# Just use `module` or the brace version of `package`. - # 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] @@ -794,10 +791,8 @@ my $actions = JSON::Tiny::Actions.new; # You've already seen `my` and `has`, we'll now explore the others. ## * `our` (happens at `INIT` time -- see "Phasers" below) -# Along with `my`, there are several others declarators you can use. -# The first one you'll want for the previous part is `our`. +# 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: module Foo::Bar { our $n = 1; # note: you can't put a type constraint on an `our` variable our sub inc { @@ -809,7 +804,7 @@ module Foo::Bar { say "Can't access me from outside, I'm my !"; } } - + say ++$n; # lexically-scoped variables are still available } say $Foo::Bar::n; #=> 1 @@ -826,7 +821,7 @@ 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 executed one time +# State variables are only initialized one time # (they exist in other langages such as C as `static`) sub fixed-rand { state $val = rand; @@ -859,7 +854,7 @@ for ^5 -> $a { ## * Compile-time phasers BEGIN { say "[*] Runs at compile time, as soon as possible, only once" } -CHECK { say "[*] Runs at compile time, instead as late as possible, only once" } +CHECK { say "[*] Runs at compile time, as late as possible, only once" } ## * Run-time phasers INIT { say "[*] Runs at run time, as soon as possible, only once" } @@ -867,10 +862,21 @@ END { say "Runs at run time, as late as possible, only once" } ## * Block phasers ENTER { say "[*] Runs everytime you enter a block, repeats on loop blocks" } -LEAVE { say "Runs everytime you leave a block, even when an exception happened. Repeats on loop blocks." } +LEAVE { say "Runs everytime you leave a block, even when an exception + happened. Repeats on loop blocks." } + +PRE { say "Asserts a precondition at every block entry, + before ENTER (especially useful for loops)" } +# exemple: +for 0..2 { + PRE { $_ > 1 } # This is going to blow up with "Precondition failed" +} -PRE { say "Asserts a precondition at every block entry, before ENTER (especially useful for loops)" } -POST { say "Asserts a postcondition at every block exit, after LEAVE (especially useful for loops)" } +POST { say "Asserts a postcondition at every block exit, + after LEAVE (especially useful for loops)" } +for 0..2 { + POST { $_ < 2 } # This is going to blow up with "Postcondition failed" +} ## * Block/exceptions phasers sub { @@ -888,12 +894,12 @@ for ^5 { ## * Role/class phasers COMPOSE { "When a role is composed into a class. /!\ NOT YET IMPLEMENTED" } -# They allow for cute trick or clever code ...: -say "This code took " ~ (time - CHECK time) ~ "s to run"; +# They allow for cute tricks or clever code ...: +say "This code took " ~ (time - CHECK time) ~ "s to compile"; # ... or clever organization: sub do-db-stuff { - ENTER $db.start-transaction; # New transaction everytime we enter the sub + $db.start-transaction; # start a new transaction KEEP $db.commit; # commit the transaction if all went well UNDO $db.rollback; # or rollback if all hell broke loose } @@ -1017,7 +1023,7 @@ sub circumfix:<[ ]>(Int $n) { $n ** $n } say [5]; #=> 3125 - # circumfix is around. Again, not whitespace. + # circumfix is around. Again, no whitespace. sub postcircumfix:<{ }>(Str $s, Int $idx) { # post-circumfix is @@ -1041,7 +1047,7 @@ postcircumfix:<{ }>(%h, $key, :delete); # (you can call operators like that) # *everything* -- with great power comes great responsibility) ## Meta operators ! -# Oh boy, get ready. Get ready, because we're dwelving deep +# 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). @@ -1049,9 +1055,9 @@ postcircumfix:<{ }>(%h, $key, :delete); # (you can call operators like that) # Basically, they're operators that apply another operator. ## * Reduce meta-operator -# It's a prefix meta-operator that takes a binary functions and +# 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 return a "default value" for this operator +# 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 @@ -1072,8 +1078,8 @@ say [//] Nil, Any, False, 1, 5; #=> False # Default value examples: -say [*] (); #=> 1 -say [+] (); #=> 0 +say [*] (); #=> 1 +say [+] (); #=> 0 # meaningless values, since N*1=N and N+0=N. say [//]; #=> (Any) # There's no "default value" for `//`. @@ -1086,7 +1092,7 @@ say [[&add]] 1, 2, 3; #=> 6 # 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 runs the an array with all these new elements. +# 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 @@ -1106,8 +1112,7 @@ say [[&add]] 1, 2, 3; #=> 6 # (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 throws you into an infinite loop, - # because Perl 6 can't figure out the end +#my @list = 1, 3, 6 ... 10; # this dies because Perl 6 can't figure out the end my @list = 1, 2, 3 ...^ 10; # as with ranges, you can exclude the last element # (the iteration when the predicate matches). my @list = 1, 3, 9 ... * > 30; # you can use a predicate @@ -1219,7 +1224,7 @@ so 'abbbbbbc' ~~ / a b ** 3..* c /; # `True` (infinite ranges are okay) # they use a more perl6-ish syntax: say 'fooa' ~~ / f <[ o a ]>+ /; #=> 'fooa' # You can use ranges: -say 'aeiou' ~~ / a <[ e..w ]> /; #=> 'aeiou' +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) say 'he-he !' ~~ / 'he-' <[ a..z \! \ ]> + /; #=> 'he-he !' @@ -1239,14 +1244,14 @@ so 'foo!' ~~ / <-[ a..z ] + [ f o ]> + /; # True (the + doesn't replace the left # 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 'fooABCABCbar' ~~ / foo [ A B C ] + bar /; +so 'foo012012bar' ~~ / foo [ '01' <[0..9]> ] + bar /; # The previous line returns `True`. -# We match the "abc" 1 or more time (the `+` was applied to the group). +# 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 B C ) + bar /; # `True`. (using `so` here, `$/` below) +so 'fooABCABCbar' ~~ / foo ( 'A' <[A..Z]> 'C' ) + bar /; # `True`. (using `so` here, `$/` below) # So, starting with the grouping explanations. # As we said before, our `Match` object is available as `$/`: @@ -1284,10 +1289,12 @@ 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<key>` for hash access and `match[idx]` for array access) +# (but you can also just use `match<key>` for hash access +# and `match[idx]` for array access) say $/[0].list.perl; #=> (Match.new(...),).list - # We can see it's a list of Match objects. Those contain a bunch of infos: - # where the match started/ended, the "ast" (see actions later), etc. + # We can see it's a list of Match objects. Those contain + # a bunch of infos: where the match started/ended, + # the "ast" (see actions later), etc. # You'll see named capture below with grammars. ## Alternatives - the `or` of regexps @@ -1325,14 +1332,14 @@ so 'ayc' ~~ / a [ b | y ] c /; # `True`. Obviously enough ... ### Extra: the MAIN subroutime # The `MAIN` subroutine is called when you run a Perl 6 file directly. -# It's very powerful, because Perl 6 actually parses the argument +# It's very powerful, because Perl 6 actually parses the arguments # and pass them as such to the sub. It also handles named argument (`--foo`) # and will even go as far as to autogenerate a `--help` sub MAIN($name) { say "Hello, $name !" } # This produces: # $ perl6 cli.pl # Usage: -# t.pl <name> +# t.pl <name> # 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` @@ -1343,9 +1350,9 @@ multi MAIN('add', $key, $value, Bool :$replace) { ... } multi MAIN('remove', $key) { ... } multi MAIN('import', File, Str :$as) { ... } # omitting parameter name # This produces: -# $ perl 6 cli.pl +# $ perl6 cli.pl # Usage: -# t.pl [--replace] add <key> <value> +# t.pl [--replace] add <key> <value> # t.pl remove <key> # t.pl [--as=<Str>] import (File) # As you can see, this is *very* powerful. @@ -1397,7 +1404,7 @@ for <well met young hero we shall meet later> { # (explained in details below). .say } - + if rand == 0 ff rand == 1 { # compare variables other than `$_` say "This ... probably will never run ..."; } @@ -1426,7 +1433,7 @@ for <well met young hero we shall meet later> { # A flip-flop can change state as many times as needed: for <test start print it stop not printing start print again stop not anymore> { .say if $_ eq 'start' ^ff^ $_ eq 'stop'; # exclude both "start" and "stop", - #=> "print this printing again" + #=> "print it print again" } # you might also use a Whatever Star, @@ -1458,4 +1465,3 @@ If you want to go further, you can: - Come along on `#perl6` at `irc.freenode.net`. The folks here are always helpful. - Check the [source of Perl 6's functions and classes](https://github.com/rakudo/rakudo/tree/nom/src/core). Rakudo is mainly written in Perl 6 (with a lot of NQP, "Not Quite Perl", a Perl 6 subset easier to implement and optimize). - Read [the language design documents](http://design.perl6.org). They explain P6 from an implementor point-of-view, but it's still very interesting. - |