diff options
Diffstat (limited to 'perl6.html.markdown')
| -rw-r--r-- | perl6.html.markdown | 360 |
1 files changed, 182 insertions, 178 deletions
diff --git a/perl6.html.markdown b/perl6.html.markdown index b178de1e..13f383fe 100644 --- a/perl6.html.markdown +++ b/perl6.html.markdown @@ -35,7 +35,8 @@ my $variable; ## * Scalars. They represent a single value. They start with a `$` 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 : @@ -66,23 +67,13 @@ my @keys = 0, 2; @array[@keys] = @letters; # Assign using an array say @array; #=> a 6 b -# There are two more kinds of lists: Parcel and Arrays. -# Parcels are immutable lists (you can't modify a list that's not assigned). -# This is a parcel: -(1, 2, 3); # Not assigned to anything. Changing an element would provoke an error -# This is a list: -my @a = (1, 2, 3); # Assigned to `@a`. Changing elements is okay! - -# Lists flatten (in list context). You'll see below how to apply item context -# or use arrays to have real nested lists. - - -## * 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 @@ -112,30 +103,6 @@ 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) { # `*@` (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, @@ -154,23 +121,20 @@ 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!) { @@ -187,11 +151,6 @@ 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(:$def = 5) { @@ -201,8 +160,29 @@ named-def; #=> 5 named-def(:10def); #=> 10 named-def(def => 15); #=> 15 -# -- Note: we're going to learn *more* on subs really soon, -# but we need to grasp a few more things to understand their real power. Ready? +# Since you can omit parenthesis to call a function with no arguments, +# you need "&" in the name to capture `say-hello`. +my &s = &say-hello; +my &other-s = sub { say "Anonymous function !" } + +# A sub can have a "slurpy" parameter, or "doesn't-matter-how-many" +sub as-many($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, $c"; +} +concat3(|@array); #=> a, b, c + # `@array` got "flattened" as a part of the argument list ### Containers # In Perl 6, values are actually stored in "containers". @@ -220,23 +200,19 @@ sub mutate($n is 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 `mod` 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, "0", "", Nil, A type (like `Str` or `Int`), # and of course False itself. # Every other value is Truthy. if True { @@ -247,30 +223,38 @@ 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/ { # Don't worry about smart matching -- 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) ~~ True {...} say "Quite a long string !"; } default { # same as `when *` (using the Whatever Star) @@ -281,7 +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 @@ -296,7 +280,7 @@ loop (my $i = 0; $i < 5; $i++) { # - `for` - Passes through an array for @array -> $variable { - say "I've found $variable !"; + say "I've got $variable !"; } # As we saw with given, for's default "current iteration" variable is `$_`. @@ -316,22 +300,15 @@ for @array { 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 $result"; } -## Loops can also have a label, and be jumped to through these. -OUTER: while 1 { - say "hey"; - while 1 { - OUTER.last; # All the control keywords must be called on the label itself - } -} - # Now that you've seen how to traverse a list, you need to be aware of something: # List context (@) flattens. If you traverse nested lists, you'll actually be traversing a -# shallow list (except if some sub-list were put in item context ($)). +# shallow list. for 1, 2, (3, (4, ((5)))) { say "Got $_."; } #=> Got 1. Got 2. Got 3. Got 4. Got 5. @@ -348,9 +325,14 @@ for [1, 2, 3, 4] { say "Got $_."; } #=> Got 1 2 3 4. -# The other difference between `$()` and `[]` is that `[]` always returns a mutable Array -# whereas `$()` will return a Parcel when given a Parcel. +# You need to be aware of when flattening happens exactly. +# The general guideline is that argument lists flatten, but not method calls. +# Also note that `.list` and array assignment flatten (`@ary = ...`) flatten. +((1,2), 3, (4,5)).map({...}); # iterates over three elements (method call) +map {...}, ((1,2),3,(4,5)); # iterates over five elements (argument list is flattened) +(@a, @b, @c).pick(1); # picks one of three arrays (method call) +pick 1, @a, @b, @c; # flattens argument list and pick one element ### Operators @@ -394,9 +376,6 @@ $arg ~~ &bool-returning-function; # `True` if the function, passed `$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; @@ -559,6 +538,21 @@ map(sub ($a, $b) { $a + $b + 3 }, @array); # (here with `sub`) # Note : those are sorted lexicographically. # `{ $^b / $^a }` is like `-> $a, $b { $b / $a }` +## About types... +# Perl6 is gradually typed. This means you can specify the type +# of your variables/arguments/return types, or you can omit them +# and they'll default to "Any". +# You obviously get access to a few base types, like Int and Str. +# The constructs for declaring types are "class", "role", +# which you'll see later. + +# For now, let us examinate "subset": +# a "subset" is a "sub-type" with additional checks. +# For example: "a very big integer is an Int that's greater than 500" +# You can specify the type you're subtyping (by default, Any), +# and add additional checks with the "where" keyword: +subset VeryBigInteger of Int where * > 500; + ## Multiple Dispatch # Perl 6 can decide which variant of a `sub` to call based on the type of the # arguments, or on arbitrary preconditions, like with a type or a `where`: @@ -567,20 +561,19 @@ map(sub ($a, $b) { $a + $b + 3 }, @array); # (here with `sub`) 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. @@ -724,7 +717,7 @@ role PrintableVal { } } -# you "use" a mixin with "does" : +# you "import" a mixin (a "role") with "does": class Item does PrintableVal { has $.val; @@ -1083,9 +1076,7 @@ postcircumfix:<{ }>(%h, $key, :delete); # (you can call operators like that) # It's a prefix meta-operator that takes a binary functions and # one or many lists. If it doesn't get passed any argument, # it either return a "default value" for this operator -# (a value that wouldn't change the result if passed as one -# of the element of the list to be passed to the operator), -# or `Any` if there's none (examples below). +# (a meaningless value) or `Any` if there's none (examples below). # # Otherwise, it pops an element from the list(s) one at a time, and applies # the binary function to the last result (or the list's first element) @@ -1107,9 +1098,7 @@ say [//] Nil, Any, False, 1, 5; #=> False # Default value examples: say [*] (); #=> 1 say [+] (); #=> 0 - # In both cases, they're results that, were they in the lists, - # wouldn't have any impact on the final value - # (since N*1=N and N+0=N). + # meaningless values, since N*1=N and N+0=N. say [//]; #=> (Any) # There's no "default value" for `//`. @@ -1163,90 +1152,6 @@ say @fib[^10]; #=> 1 1 2 3 5 8 13 21 34 55 # That's why `@primes[^100]` will take a long time the first time you print # it, then be instant. - -## * Sort comparison -# They return one value of the `Order` enum : `Less`, `Same` and `More` -# (which numerify to -1, 0 or +1). -1 <=> 4; # sort comparison for numerics -'a' leg 'b'; # sort comparison for string -$obj eqv $obj2; # sort comparison using eqv semantics - -## * Generic ordering -3 before 4; # True -'b' after 'a'; # True - -## * Short-circuit default operator -# Like `or` and `||`, but instead returns the first *defined* value : -say Any // Nil // 0 // 5; #=> 0 - -## * Short-circuit exclusive or (XOR) -# Returns `True` if one (and only one) of its arguments is true -say True ^^ False; #=> True - -## * Flip Flop -# The flip flop operators (`ff` and `fff`, equivalent to P5's `..`/`...`). -# are operators that take two predicates to test: -# They are `False` until their left side returns `True`, then are `True` until -# their right side returns `True`. -# Like for ranges, you can exclude the iteration when it became `True`/`False` -# by using `^` on either side. -# Let's start with an example : -for <well met young hero we shall meet later> { - # by default, `ff`/`fff` smart-match (`~~`) against `$_`: - 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 $_ > 50 ff *; # Once the flip-flop reaches a number greater than 50, - # it'll never go back to `False` - #=> 60 3 40 60 -} - -# You can also use this property to create an `If` -# that'll not go through the first time : -for <a b c> { - .say if * ^ff *; # the flip-flop is `True` and never goes back to `False`, - # but the `^` makes it *not run* on the first iteration - #=> b c -} - - ### Regular Expressions # I'm sure a lot of you have been waiting for this one. # Well, now that you know a good deal of Perl 6 already, we can get started. @@ -1470,6 +1375,105 @@ multi MAIN('import', File, Str :$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: @@ -1477,5 +1481,5 @@ 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. |