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Diffstat (limited to 'perl6.html.markdown')
| -rw-r--r-- | perl6.html.markdown | 566 |
1 files changed, 348 insertions, 218 deletions
diff --git a/perl6.html.markdown b/perl6.html.markdown index fca863af..3bb87916 100644 --- a/perl6.html.markdown +++ b/perl6.html.markdown @@ -10,8 +10,7 @@ contributors: Perl 6 is a highly capable, feature-rich programming language made for the upcoming hundred years. -Perl 6 runs on [the Parrot VM](http://parrot.org/), the JVM -and [the MoarVM](http://moarvm.com). +Perl 6 runs on [the MoarVM](http://moarvm.com) and the JVM. Meta-note : the triple pound signs are here to denote headlines, double paragraphs, and single notes. @@ -30,12 +29,13 @@ double paragraphs, and single notes. # In Perl 6, you declare a lexical variable using `my` my $variable; -# Perl 6 has 4 variable types : +# Perl 6 has 4 kinds of variables: ## * Scalars. They represent a single value. They start with a `$` my $str = 'String'; -my $str2 = "String"; # double quotes allow for interpolation +# 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 : @@ -46,24 +46,33 @@ my $inverse = !$bool; # You can invert a bool with the prefix `!` operator my $forced-bool = so $str; # And you can use the prefix `so` operator # which turns its operand into a Bool -## * Arrays. They represent multiple values. Their name start with `@`. +## * Lists. They represent multiple values. Their name start with `@`. -my @array = 1, 2, 3; my @array = 'a', 'b', 'c'; # equivalent to : -my @array = <a b c>; # array of words, delimited by space. +my @letters = <a b c>; # array of words, delimited by space. # 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 -say "Interpolate an array using [] : @array[]"; #=> Interpolate an array using [] : a b c +say "Interpolate an array using [] : @array[]"; +#=> Interpolate an array using [] : 1 2 3 + +@array[0] = -1; # Assign a new value to an array index +@array[0, 1] = 5, 6; # Assign multiple values + +my @keys = 0, 2; +@array[@keys] = @letters; # Assign using an array +say @array; #=> a 6 b -## * Hashes. Key-Value Pairs. -# Hashes are actually arrays of Pairs (`Key => Value`), -# except they get "flattened", removing duplicated keys. +## * Hashes, or key-value Pairs. +# Hashes are actually arrays of Pairs +# (you can construct a Pair object using the syntax `Key => Value`), +# except they get "flattened" (hash context), removing duplicated keys. my %hash = 1 => 2, 3 => 4; -my %hash = autoquoted => "key", # keys *can* get auto-quoted +my %hash = autoquoted => "key", # keys get auto-quoted "some other" => "value", # trailing commas are okay ; my %hash = <key1 value1 key2 value2>; # you can also create a hash @@ -93,30 +102,6 @@ sub say-hello-to(Str $name) { # You can provide the type of an argument say "Hello, $name !"; } -# Since you can omit parenthesis to call a function with no arguments, -# you need "&" in the name to capture `say-hello`. -my &s = &say-hello; -my &other-s = sub { say "Anonymous function !" } - -# A sub can have a "slurpy" parameter, or "doesn't-matter-how-many" -sub as-many($head, *@rest) { # The `*@` slurpy will basically "take everything else". - # Note: you can have parameters *before* (like here) - # a slurpy one, but not *after*. - say @rest.join(' / ') ~ " !"; -} -say as-many('Happy', 'Happy', 'Birthday'); #=> Happy / Birthday ! - # Note that the splat did not 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) -sub concat3($a, $b, $c) { - say "$a, $b, $c"; -} -concat3(|@array); #=> a, b, c - # `@array` got "flattened" as a part of the argument list - ## It can also have optional arguments: sub with-optional($arg?) { # the "?" marks the argument optional say "I might return `(Any)` if I don't have an argument passed, @@ -135,23 +120,20 @@ hello-to; #=> Hello, World ! hello-to(); #=> Hello, World ! hello-to('You'); #=> Hello, You ! -## You can also, by using a syntax akin to the one of hashes (yay unification !), +## 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). 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 paramater, +# which means this fails: +with-named(1, 'named' => 6); with-named(2, :named(5)); #=> 7 -with-named(3, :4named); #=> 7 - # (special colon pair syntax for numbers, - # to be used with s// and such, see later) - -with-named(3); # warns, because we tried to use the undefined $named in a `+`: - # by default, named arguments are *optional* # To make a named argument mandatory, you can use `?`'s inverse, `!` sub with-mandatory-named(:$str!) { @@ -168,22 +150,37 @@ sub takes-a-bool($name, :$bool) { # ... you can use the same "short boolean" hash syntax: takes-a-bool('config', :bool); # config takes True takes-a-bool('config', :!bool); # config takes False -# or you can use the "adverb" form: -takes-a-bool('config'):bool; #=> config takes True -takes-a-bool('config'):!bool; #=> config takes False -# You'll learn to love (or maybe hate, eh) that syntax later. - ## You can also provide your named arguments with defaults: sub named-def(:$def = 5) { say $def; } named-def; #=> 5 -named-def(:10def); #=> 10 named-def(def => 15); #=> 15 -# -- Note: we're going to learn *more* on subs really soon, -# but we need to grasp a few more things to understand their real power. Ready? +# Since you can omit parenthesis to call a function with no arguments, +# you need "&" in the name to capture `say-hello`. +my &s = &say-hello; +my &other-s = sub { say "Anonymous function !" } + +# A sub can have a "slurpy" parameter, or "doesn't-matter-how-many" +sub as-many($head, *@rest) { # `*@` (slurpy) will basically "take everything else". + # Note: you can have parameters *before* (like here) + # a slurpy one, but not *after*. + say @rest.join(' / ') ~ " !"; +} +say as-many('Happy', 'Happy', 'Birthday'); #=> Happy / Birthday ! + # Note that the splat did not 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) +sub concat3($a, $b, $c) { + say "$a, $b, $c"; +} +concat3(|@array); #=> a, b, c + # `@array` got "flattened" as a part of the argument list ### Containers # In Perl 6, values are actually stored in "containers". @@ -191,7 +188,7 @@ named-def(def => 15); #=> 15 # its right. When passed around, containers are marked as immutable. # Which means that, in a function, you'll get an error if you try to # mutate one of your arguments. -# If you really need to, you can ask for a mutable container using `is rw` : +# If you really need to, you can ask for a mutable container using `is rw`: sub mutate($n is rw) { $n++; say "\$n is now $n !"; @@ -199,25 +196,21 @@ sub mutate($n is rw) { # If what you want is 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 mod() is rw { $x } -mod() = 52; # in this case, the parentheses are mandatory - # (else Perl 6 thinks `mod` is a "term") +sub x-store() is rw { $x } +x-store() = 52; # in this case, the parentheses are mandatory + # (else Perl 6 thinks `x-store` is an identifier) say $x; #=> 52 ### Control Flow Structures - -# You don't need to put parenthesis around the condition, -# but that also means you always have to use brackets (`{ }`) for their body : - ## Conditionals # - `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, "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 { @@ -228,30 +221,40 @@ 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: +# if (true) say; # This doesn't work ! + # You can also use their postfix versions, with the keyword after: say "Quite truthy" if True; -# if (true) say; # This doesn't work ! - # - 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 # powerful thanks to smart matching and thanks to 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" { - when /foo/ { # You'll read about the smart-matching operator below -- just know `when` uses it. + say $_; #=> foo bar + when /foo/ { # Don't worry about smart matching yet – just know `when` uses it. # This is equivalent to `if $_ ~~ /foo/`. say "Yay !"; } when $_.chars > 50 { # smart matching anything with True (`$a ~~ True`) is True, # so you can also put "normal" conditionals. + # This when is equivalent to this `if`: + # if $_ ~~ ($_.chars > 50) {...} + # Which means: + # if $_.chars > 50 {...} say "Quite a long string !"; } default { # same as `when *` (using the Whatever Star) @@ -262,7 +265,7 @@ given "foo bar" { ## Looping constructs # - `loop` is an infinite loop if you don't pass it arguments, -# but can also be a c-style `for` : +# but can also be a C-style `for` loop: loop { say "This is an infinite loop !"; last; # last breaks out of the loop, like the `break` keyword in other languages @@ -270,18 +273,18 @@ loop { loop (my $i = 0; $i < 5; $i++) { next if $i == 3; # `next` skips to the next iteration, like `continue` - # in other languages. Note that you can also use postfix conditionals, - # loops, etc. + # in other languages. Note that you can also use postfix + # conditionals, loops, etc. say "This is a C-style for loop !"; } # - `for` - Passes through an array for @array -> $variable { - say "I've found $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 when. +# That means you can use `when` in a `for` just like you were in a `given`. for @array { say "I've got $_"; @@ -292,28 +295,29 @@ for @array { for @array { # You can... - next if $_ == 3; # Skip to the next iteration (like `continue` 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). } -# Note - the "lambda" `->` syntax isn't reserved to `for` : +# 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 $result"; } ### Operators -## Since Perl languages are very much operator-based languages +## Since Perl languages are very much operator-based languages, ## Perl 6 operators are actually just funny-looking subroutines, in syntactic ## categories, like infix:<+> (addition) or prefix:<!> (bool not). -## The categories are : -# - "prefix" : before (like `!` in `!True`). -# - "postfix" : after (like `++` in `$a++`). -# - "infix" : in between (like `*` in `4 * 3`). -# - "circumfix" : around (like `[`-`]` in `[1, 2]`). -# - "post-circumfix" : around, after another term (like `{`-`}` in `%hash{'key'}`) +## The categories are: +# - "prefix": before (like `!` in `!True`). +# - "postfix": after (like `++` in `$a++`). +# - "infix": in between (like `*` in `4 * 3`). +# - "circumfix": around (like `[`-`]` in `[1, 2]`). +# - "post-circumfix": around, after another term (like `{`-`}` in `%hash{'key'}`) ## The associativity and precedence list are explained below. @@ -334,7 +338,8 @@ if long-computation() -> $result { (1, 2) eqv (1, 3); # - `~~` is smart matching -# For a complete list of combinations, use this table : http://perlcabal.org/syn/S03.html#Smart_matching +# For a complete list of combinations, use this table: +# http://perlcabal.org/syn/S03.html#Smart_matching 'a' ~~ /a/; # true if matches regexp 'key' ~~ %hash; # true if key exists in hash $arg ~~ &bool-returning-function; # `True` if the function, passed `$arg` @@ -343,9 +348,6 @@ $arg ~~ &bool-returning-function; # `True` if the function, passed `$arg` 1 ~~ True; # smart-matching against a boolean always returns that boolean # (and will warn). -# - `===` is value identity and uses `.WHICH` on the objects to compare them -# - `=:=` is container identity and uses `VAR()` on the objects to compare them - # You also, of course, have `<`, `<=`, `>`, `>=`. # Their string equivalent are also avaiable : `lt`, `le`, `gt`, `ge`. 3 > 4; @@ -357,18 +359,29 @@ $arg ~~ &bool-returning-function; # `True` if the function, passed `$arg` # This also works as a shortcut for `0..^N`: ^10; # means 0..^10 -# This also allows us to demonstrate that Perl 6 has lazy arrays, +# This also allows us to demonstrate that Perl 6 has lazy/infinite arrays, # using the Whatever Star: -my @array = 1..*; # 1 to Infinite ! +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. - -# Warning, though: if you try this example in the REPL and just put `1..*`, -# Perl 6 will be forced to try and evaluate the whole array (to print it), -# so you'll end with an infinite loop. +# It also will never calculate more elements that are needed. + +# An array subscript can also be a closure. +# It'll be called with the length as the argument +say join(' ', @array[15..*]); #=> 15 16 17 18 19 +# which is equivalent to: +say join(' ', @array[-> $n { 15..$n }]); + +# 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 +@numbers[5..*] = 3, 9 ... *; # even though the sequence is infinite, + # only the 15 needed values will be calculated. +say @numbers; #=> 0 1 2 3 4 3 9 15 21 [...] 81 87 + # (only 20 values) ## * And, Or 3 && 4; # 4, which is Truthy. Calls `.Bool` on `4` and gets `True`. @@ -380,7 +393,7 @@ $a && $b && $c; # Returns the first argument that evaluates to False, $a || $b; # And because you're going to want them, -# you also have composed assignment operators: +# you also have compound assignment operators: $a *= 2; # multiply and assignment $b %%= 5; # divisible by and assignment @array .= sort; # calls the `sort` method and assigns the result back @@ -390,7 +403,7 @@ $b %%= 5; # divisible by and assignment # a few more key concepts that make them better than in any other language :-). ## Unpacking ! -# It's the ability to "extract" arrays and keys. +# It's the ability to "extract" arrays and keys (AKA "destructuring"). # It'll work in `my`s and in parameter lists. my ($a, $b) = 1, 2; say $a; #=> 1 @@ -415,7 +428,7 @@ first-of-array(@tail); # Throws an error "Too many positional parameters passed" # (which means the array is too big). # You can also use a slurp ... -sub slurp-in-array(@ [$fst, *@rest]) { # you could decide to keep `*@rest` anonymous +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`. } @@ -485,7 +498,8 @@ sub truthy-array(@array) { # 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); # also works. Same as `-> $a, $b { $a + $b + 3 }` +my @arrayplus3 = map(*+*+3, @array); # Same as `-> $a, $b { $a + $b + 3 }` + # also `sub ($a, $b) { $a + $b + 3 }` say (*/2)(4); #=> 2 # Immediatly execute the function Whatever created. say ((*+3)/5)(5); #=> 1.6 @@ -494,11 +508,27 @@ say ((*+3)/5)(5); #=> 1.6 # But if you need to have more than one argument (`$_`) # in a block (without wanting to resort to `-> {}`), # you can also use the implicit argument syntax, `$^` : -map({ $^a + $^b + 3 }, @array); # same as the above +map({ $^a + $^b + 3 }, @array); # equivalent to following: +map(sub ($a, $b) { $a + $b + 3 }, @array); # (here with `sub`) # Note : those are sorted lexicographically. # `{ $^b / $^a }` is like `-> $a, $b { $b / $a }` +## About types... +# 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 examinate "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 # 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`: @@ -507,20 +537,19 @@ map({ $^a + $^b + 3 }, @array); # same as the above multi sub sayit(Int $n) { # note the `multi` keyword here say "Number: $n"; } -multi sayit(Str $s) } # the `sub` is the default +multi sayit(Str $s) { # a multi is a `sub` by default say "String: $s"; } sayit("foo"); # prints "String: foo" sayit(True); # fails at *compile time* with # "calling 'sayit' will never work with arguments of types ..." -# with arbitrary precondition: +# 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) multi is-big(Int $) { "No" } -# You can also name these checks, by creating "subsets": subset Even of Int where * %% 2; multi odd-or-even(Even) { "Even" } # The main case using the type. @@ -576,7 +605,7 @@ sub foo { bar(); # call `bar` in-place } sub bar { - say $*foo; # Perl 6 will look into the call stack instead, and find `foo`'s `$*a`, + say $*foo; # `$*a` will be looked in the call stack, and find `foo`'s, # even though the blocks aren't nested (they're call-nested). #=> 1 } @@ -589,8 +618,9 @@ sub bar { # but you have `$.` to get a public (immutable) accessor along with it. # (using `$.` is like using `$!` plus a `method` with the same name) -# (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) +# (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. @@ -599,7 +629,7 @@ class A { has Int $!private-field = 10; method get-value { - $.field + $!private-field + $n; + $.field + $!private-field; } method set-value($n) { @@ -617,7 +647,7 @@ class A { # Create a new instance of A with $.field set to 5 : # Note: you can't set private-field from here (more later on). my $a = A.new(field => 5); -$a.get-value; #=> 18 +$a.get-value; #=> 15 #$a.field = 5; # This fails, because the `has $.field` is immutable $a.other-field = 10; # This, however, works, because the public field # is mutable (`rw`). @@ -663,7 +693,7 @@ role PrintableVal { } } -# you "use" a mixin with "does" : +# you "import" a mixin (a "role") with "does": class Item does PrintableVal { has $.val; @@ -685,7 +715,7 @@ class Item does PrintableVal { } ### Exceptions -# Exceptions are built on top of classes, usually in the package `X` (like `X::IO`). +# Exceptions are built on top of classes, in the package `X` (like `X::IO`). # Unlike many other languages, in Perl 6, you put the `CATCH` block *within* the # block to `try`. By default, a `try` has a `CATCH` block that catches # any exception (`CATCH { default {} }`). @@ -695,21 +725,43 @@ try { open 'foo'; CATCH { when X::AdHoc { say "unable to open file !" } - # any other exception will be re-raised, since we don't have a `default` + # Any other exception will be re-raised, since we don't have a `default` + # Basically, if a `when` matches (or there's a `default`) marks the exception as + # "handled" so that it doesn't get re-thrown from the `CATCH`. + # You still can re-throw the exception (see below) by hand. } } # You can throw an exception using `die`: die X::AdHoc.new(payload => 'Error !'); -# TODO warn -# TODO fail -# TODO CONTROL + +# You can access the last exception with `$!` (usually used 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 +# 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"; + CATCH { + default { say "It threw because we try to get the fail's value!" } + } +} + +# There is also another kind of exception: Control exceptions. +# Those are "good" exceptions, which happen when you change your program's flow, +# using operators like `return`, `next` or `last`. +# You can "catch" those with `CONTROL` (not 100% working in Rakudo yet). ### Packages # 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) -# Packages play a big part in a language, especially as Perl is well-known for CPAN, +# 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`: @@ -719,7 +771,7 @@ module Hello::World { # Bracketed form # ... declarations here ... } module Parse::Text; # file-scoped form -grammar Parse::Text::Grammar { # A grammar is a fine package, which you could `use` +grammar Parse::Text::Grammar { # A grammar is a package, which you could `use` } # NOTE for Perl 5 users: even though the `package` keyword exists, @@ -841,7 +893,7 @@ say "This code took " ~ (time - CHECK time) ~ "s to run"; # ... or clever organization: sub do-db-stuff { - ENTER $db.start-transaction; # create a new transaction everytime we enter the sub + ENTER $db.start-transaction; # New transaction everytime we enter the sub KEEP $db.commit; # commit the transaction if all went well UNDO $db.rollback; # or rollback if all hell broke loose } @@ -888,7 +940,7 @@ say join ',', gather if False { # But consider: constant thrice = gather for ^3 { say take $_ }; # Doesn't print anything # versus: -constant thrice = eager gather for ^3 { say take $_ }; #=> 0 1 2 3 4 +constant thrice = eager gather for ^3 { say take $_ }; #=> 0 1 2 # - `lazy` - Defer actual evaluation until value is fetched (forces lazy context) # Not yet implemented !! @@ -951,7 +1003,7 @@ say 5!; #=> 120 sub infix:<times>(Int $n, Block $r) { # infix in the middle for ^$n { $r(); # You need the explicit parentheses to call the function in `$r`, - # else you'd be referring at the variable itself, kind of like with `&r`. + # else you'd be referring at the variable itself, like with `&r`. } } 3 times -> { say "hello" }; #=> hello @@ -1000,12 +1052,11 @@ postcircumfix:<{ }>(%h, $key, :delete); # (you can call operators like that) # It's a prefix meta-operator that takes a binary functions and # one or many lists. If it doesn't get passed any argument, # it either return a "default value" for this operator -# (a value that wouldn't change the result if passed as one -# of the element of the list to be passed to the operator), -# or `Any` if there's none (examples below). +# (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. +# 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 @@ -1023,9 +1074,7 @@ say [//] Nil, Any, False, 1, 5; #=> False # Default value examples: say [*] (); #=> 1 say [+] (); #=> 0 - # In both cases, they're results that, were they in the lists, - # wouldn't have any impact on the final value - # (since N*1=N and N+0=N). + # meaningless values, since N*1=N and N+0=N. say [//]; #=> (Any) # There's no "default value" for `//`. @@ -1065,99 +1114,20 @@ my @list = 1, 3, 9 ... * > 30; # you can use a predicate # (with the Whatever Star, here). my @list = 1, 3, 9 ... { $_ > 30 }; # (equivalent to the above) -my @fib = 1, 1, *+* ... *; # lazy infinite list of prime numbers, +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. + 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. - -## * Sort comparison -# They return one value of the `Order` enum : `Less`, `Same` and `More` -# (which numerify to -1, 0 or +1). -1 <=> 4; # sort comparison for numerics -'a' leg 'b'; # sort comparison for string -$obj eqv $obj2; # sort comparison using eqv semantics - -## * Generic ordering -3 before 4; # True -'b' after 'a'; # True - -## * Short-circuit default operator -# Like `or` and `||`, but instead returns the first *defined* value : -say Any // Nil // 0 // 5; #=> 5 - -## * Short-circuit exclusive or (XOR) -# Returns `True` if one (and only one) of its arguments is true -say True ^^ False; #=> True - -## * Flip Flop -# The flip flop operators (`ff` and `fff`, equivalent to P5's `..`/`...`). -# are operators that take two predicates to test: -# They are `False` until their left side returns `True`, then are `True` until -# their right side returns `True`. -# Like for ranges, you can exclude the iteration when it became `True`/`False` -# by using `^` on either side. -# Let's start with an example : -for <well met young hero we shall meet later> { - # by default, `ff`/`fff` smart-match (`~~`) against `$_`: - if 'met' ^ff 'meet' { # Won't enter the if for "met" - # (explained in details below). - .say - } - - if rand == 0 ff rand == 1 { # compare variables other than `$_` - say "This ... probably will never run ..."; - } -} -# This will print "young hero we shall meet" (excluding "met"): -# the flip-flop will start returning `True` when it first encounters "met" -# (but will still return `False` for "met" itself, due to the leading `^` -# on `ff`), until it sees "meet", which is when it'll start returning `False`. - -# The difference between `ff` (awk-style) and `fff` (sed-style) is that -# `ff` will test its right side right when its left side changes to `True`, -# and can get back to `False` right away -# (*except* it'll be `True` for the iteration that matched) - -# While `fff` will wait for the next iteration to -# try its right side, once its left side changed: -.say if 'B' ff 'B' for <A B C B A>; #=> B B - # because the right-hand-side was tested - # directly (and returned `True`). - # "B"s are still printed since it matched that time - # (it just went back to `False` right away). -.say if 'B' fff 'B' for <A B C B A>; #=> B C B - # because the right-hand-side wasn't tested until - # `$_` became "C" - # (and thus did not match instantly). - -# A flip-flop can change state as many times as needed: -for <test start print this stop you stopped printing start printing again stop not anymore> { - .say if $_ eq 'start' ^ff^ $_ eq 'stop'; # exclude both "start" and "stop", - #=> "print this printing again" -} - -# you might also use a Whatever Star, -# which is equivalent to `True` for the left side or `False` for the right: -for (1, 3, 60, 3, 40, 60) { # Note: the parenthesis are superfluous here - # (sometimes called "superstitious parentheses") - .say if $_ > 50 ff *; # Once the flip-flop reaches a number greater than 50, - # it'll never go back to `False` - #=> 60 3 40 60 -} - -# You can also use this property to create an `If` -# that'll not go through the first time : -for <a b c> { - .say if * ^ff *; # the flip-flop is `True` and never goes back to `False`, - # but the `^` makes it *not run* on the first iteration - #=> b c -} - - ### Regular Expressions # I'm sure a lot of you have been waiting for this one. # Well, now that you know a good deal of Perl 6 already, we can get started. @@ -1190,8 +1160,8 @@ say so 'a' ~~ / a /; # More readable with some spaces! # a regexp. We're converting the result using `so`, but in fact, it's # returning a `Match` object. They know how to respond to list indexing, # hash indexing, and return the matched string. -# The results of the match are also available as `$/` (implicitly lexically-scoped). -# You can also use the capture variables (`$0`, `$1`, ... - starting at 0, not 1 !). +# The results of the match are available as `$/` (implicitly lexically-scoped). +# You can also use the capture variables (`$0`, `$1`, ... starting at 0, not 1 !). # # You can also note that `~~` does not perform start/end checking # (meaning the regexp can be matched with just one char of the string), @@ -1233,9 +1203,9 @@ so 'abbbbc' ~~ / a b+ c /; # `True`, matched 4 "b"s 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, but can't be something else. +so 'aec' ~~ / a b* c /; # `False`. "b"(s) are optional, not replaceable. -# - `**` - "Quantify It Yourself". +# - `**` - (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) @@ -1244,6 +1214,27 @@ so 'abbbc' ~~ / a b ** 1..3 c /; # `True` so 'abbbbbbc' ~~ / a b ** 1..3 c /; # `False` (too much) so 'abbbbbbc' ~~ / a b ** 3..* c /; # `True` (infinite ranges are okay) +# - `<[]>` - Character classes +# Character classes are the equivalent of PCRE's `[]` classes, but +# they use a more perl6-ish syntax: +say 'fooa' ~~ / f <[ o a ]>+ /; #=> 'fooa' +# You can use ranges: +say 'aeiou' ~~ / a <[ e..w ]> /; #=> 'aeiou' +# 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) +so 'foo' ~~ / <-[ f o ]> + /; # False + +# ... and compose them: : +so 'foo' ~~ / <[ a..z ] - [ f o ]> + /; # False (any letter except f and o) +so 'foo' ~~ / <-[ a..z ] + [ f o ]> + /; # True (no letter except f and o) +so 'foo!' ~~ / <-[ a..z ] + [ f o ]> + /; # True (the + doesn't replace the left part) + ## Grouping and capturing # Group: you can group parts of your regexp with `[]`. # These groups are *not* captured (like PCRE's `(?:)`). @@ -1255,7 +1246,7 @@ so 'fooABCABCbar' ~~ / foo [ A B C ] + bar /; # 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`. (we keep `so` here and use `$/` below) +so 'fooABCABCbar' ~~ / foo ( A B C ) + bar /; # `True`. (using `so` here, `$/` below) # So, starting with the grouping explanations. # As we said before, our `Match` object is available as `$/`: @@ -1271,7 +1262,7 @@ say $0; # The same as above. # 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 any `**`, but not with `?`). +# (so, with `*`, `+` and `**` (whatever the operands), but not with `?`). # Let's use examples to see that: so 'fooABCbar' ~~ / foo ( A B C )? bar /; # `True` say $/[0]; #=> ｢ABC｣ @@ -1285,30 +1276,68 @@ say $0.WHAT; #=> (Array) # A specific quantifier will always capture an Array, # may it be a range or a specific value (even 1). -# If you're wondering how the captures are numbered, here's an explanation: -TODO use graphs from s05 +# The captures are indexed per nesting. This means a group in a group will be nested +# under its parent group: `$/[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<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. + # You'll see named capture below with grammars. ## Alternatives - the `or` of regexps # WARNING: They are DIFFERENT from PCRE regexps. so 'abc' ~~ / a [ b | y ] c /; # `True`. Either "b" or "y". so 'ayc' ~~ / a [ b | y ] c /; # `True`. Obviously enough ... +# The difference between this `|` and the one you're used to is LTM. +# LTM means "Longest Token Matching". This means that the engine will always +# try to match as much as possible in the strng +'foo' ~~ / fo | foo /; # `foo`, because it's longer. +# To decide which part is the "longest", it first splits the regex in two parts: +# The "declarative prefix" (the part that can be statically analyzed) +# and the procedural parts. +# Declarative prefixes include alternations (`|`), conjuctions (`&`), +# 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. +# Exemples: +# DECLARATIVE | PROCEDURAL +/ 'foo' \d+ [ <subrule1> || <subrule2> ] /; +# DECLARATIVE (nested groups are not a problem) +/ \s* [ \w & b ] [ c | d ] /; +# However, closures and recursion (of named regexps) are procedural. +# ... There are also more complicated rules, like specificity +# (literals win over character classes) + +# Note: the first-matching `or` still exists, but is now spelled `||` +'foo' ~~ / fo || foo /; # `fo` now. + + + + ### 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 # 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, you !" } +sub MAIN($name) { say "Hello, $name !" } # This produces: # $ perl6 cli.pl # Usage: # 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 get `--replace` +# (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, then check the file exists +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', $key) { ... } @@ -1322,10 +1351,111 @@ multi MAIN('import', File, Str :$as) { ... } # omitting parameter name # As you can see, this is *very* powerful. # It even went as far as to show inline the constants. # (the type is only displayed if the argument is `$`/is named) + +### +### APPENDIX A: +### +### List of things +### + +# It's considered by now you know the Perl6 basics. +# This section is just here to list some common operations, +# but which are not in the "main part" of the tutorial to bloat it up + +## Operators + + +## * Sort comparison +# They return one value of the `Order` enum : `Less`, `Same` and `More` +# (which numerify to -1, 0 or +1). +1 <=> 4; # sort comparison for numerics +'a' leg 'b'; # sort comparison for string +$obj eqv $obj2; # sort comparison using eqv semantics + +## * Generic ordering +3 before 4; # True +'b' after 'a'; # True + +## * Short-circuit default operator +# Like `or` and `||`, but instead returns the first *defined* value : +say Any // Nil // 0 // 5; #=> 0 + +## * Short-circuit exclusive or (XOR) +# Returns `True` if one (and only one) of its arguments is true +say True ^^ False; #=> True +## * Flip Flop +# The flip flop operators (`ff` and `fff`, equivalent to P5's `..`/`...`). +# are operators that take two predicates to test: +# They are `False` until their left side returns `True`, then are `True` until +# their right side returns `True`. +# Like for ranges, you can exclude the iteration when it became `True`/`False` +# by using `^` on either side. +# Let's start with an example : +for <well met young hero we shall meet later> { + # by default, `ff`/`fff` smart-match (`~~`) against `$_`: + if 'met' ^ff 'meet' { # Won't enter the if for "met" + # (explained in details below). + .say + } + + if rand == 0 ff rand == 1 { # compare variables other than `$_` + say "This ... probably will never run ..."; + } +} +# This will print "young hero we shall meet" (excluding "met"): +# the flip-flop will start returning `True` when it first encounters "met" +# (but will still return `False` for "met" itself, due to the leading `^` +# on `ff`), until it sees "meet", which is when it'll start returning `False`. + +# The difference between `ff` (awk-style) and `fff` (sed-style) is that +# `ff` will test its right side right when its left side changes to `True`, +# and can get back to `False` right away +# (*except* it'll be `True` for the iteration that matched) - +# While `fff` will wait for the next iteration to +# try its right side, once its left side changed: +.say if 'B' ff 'B' for <A B C B A>; #=> B B + # because the right-hand-side was tested + # directly (and returned `True`). + # "B"s are printed since it matched that time + # (it just went back to `False` right away). +.say if 'B' fff 'B' for <A B C B A>; #=> B C B + # The right-hand-side wasn't tested until + # `$_` became "C" + # (and thus did not match instantly). + +# A flip-flop can change state as many times as needed: +for <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" +} + +# you might also use a Whatever Star, +# which is equivalent to `True` for the left side or `False` for the right: +for (1, 3, 60, 3, 40, 60) { # Note: the parenthesis are superfluous here + # (sometimes called "superstitious parentheses") + .say if $_ > 50 ff *; # Once the flip-flop reaches a number greater than 50, + # it'll never go back to `False` + #=> 60 3 40 60 +} + +# You can also use this property to create an `If` +# that'll not go through the first time : +for <a b c> { + .say if * ^ff *; # the flip-flop is `True` and never goes back to `False`, + # but the `^` makes it *not run* on the first iteration + #=> b c +} + + +# - `===` is value identity and uses `.WHICH` on the objects to compare them +# - `=:=` is container identity and uses `VAR()` on the objects to compare them + ``` If you want to go further, you can: + - Read the [Perl 6 Advent Calendar](http://perl6advent.wordpress.com/). This is probably the greatest source of Perl 6 information, snippets and such. - 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 [Synopses](perlcabal.org/syn). They explain it from an implementor point-of-view, but it's still very interesting. + - Read [the language design documents](http://design.perl6.org). They explain P6 from an implementor point-of-view, but it's still very interesting. + |