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----
-category: language
-language: perl6
-filename: learnperl6.p6
-contributors:
- - ["vendethiel", "http://github.com/vendethiel"]
- - ["Samantha McVey", "https://cry.nu"]
----
-
-Perl 6 is a highly capable, feature-rich programming language made for at
-least the next hundred years.
-
-The primary Perl 6 compiler is called [Rakudo](http://rakudo.org), which runs on
-the JVM and [the MoarVM](http://moarvm.com).
-
-Meta-note: double pound signs (`##`) are used to indicate paragraphs,
-while single pound signs (`#`) indicate notes.
-
-`#=>` represents the output of a command.
-
-```perl6
-# Single line comments start with a pound sign.
-
-#`( Multiline comments use #` and a quoting construct.
- (), [], {}, 「」, etc, will work.
-)
-
-# Use the same syntax for multiline comments to embed comments.
-for #`(each element in) @array {
- put #`(or print element) $_ #`(with newline);
-}
-```
-
-## Variables
-
-```perl6
-## In Perl 6, you declare a lexical variable using the `my` keyword:
-my $variable;
-## Perl 6 has 3 basic types of variables: scalars, arrays, and hashes.
-```
-
-### Scalars
-
-```perl6
-# Scalars represent a single value. They start with the `$` sigil:
-my $str = 'String';
-
-# Double quotes allow for interpolation (which we'll see later):
-my $str2 = "String";
-
-## Variable names can contain but not end with simple quotes and dashes,
-## and can contain (and end with) underscores:
-my $person's-belongings = 'towel'; # this works!
-
-my $bool = True; # `True` and `False` are Perl 6's boolean values.
-my $inverse = !$bool; # Invert a bool with the prefix `!` operator.
-my $forced-bool = so $str; # And you can use the prefix `so` operator
-$forced-bool = ?$str; # to turn its operand into a Bool. Or use `?`.
-```
-
-### Arrays and Lists
-
-```perl6
-## Arrays represent multiple values. An array variable starts with the `@`
-## sigil. Unlike lists, from which arrays inherit, arrays are mutable.
-
-my @array = 'a', 'b', 'c';
-# equivalent to:
-my @letters = <a b c>; # array of words, delimited by space.
- # Similar to perl5's qw, or Ruby's %w.
-@array = 1, 2, 3;
-
-say @array[2]; # Array indices start at 0. Here the third element
- # is being accessed.
-
-say "Interpolate an array using []: @array[]";
-#=> Interpolate an array using []: 1 2 3
-
-@array[0] = -1; # Assigning a new value to an array index
-@array[0, 1] = 5, 6; # Assigning multiple values
-
-my @keys = 0, 2;
-@array[@keys] = @letters; # Assignment using an array containing index values
-say @array; #=> a 6 b
-```
-
-### Hashes, or key-value Pairs.
-
-```perl6
-## Hashes are pairs of keys and values. You can construct a `Pair` object
-## using the syntax `Key => Value`. Hash tables are very fast for lookup,
-## and are stored unordered. Keep in mind that keys get "flattened" in hash
-## context, and any duplicated keys are deduplicated.
-my %hash = 'a' => 1, 'b' => 2;
-
-%hash = a => 1, # keys get auto-quoted when => (fat comma) is used.
- b => 2, # Trailing commas are okay.
-;
-
-## Even though hashes are internally stored differently than arrays,
-## Perl 6 allows you to easily create a hash from an even numbered array:
-%hash = <key1 value1 key2 value2>; # Or:
-%hash = "key1", "value1", "key2", "value2";
-
-%hash = key1 => 'value1', key2 => 'value2'; # same result as above
-
-## You can also use the "colon pair" syntax. This syntax is especially
-## handy for named parameters that you'll see later.
-%hash = :w(1), # equivalent to `w => 1`
- :truey, # equivalent to `:truey(True)` or `truey => True`
- :!falsey, # equivalent to `:falsey(False)` or `falsey => False`
-;
-## The :truey and :!falsey constructs are known as the
-## `True` and `False` shortcuts respectively.
-
-say %hash{'key1'}; # You can use {} to get the value from a key.
-say %hash<key2>; # If it's a string without spaces, you can actually use
- # <> (quote-words operator). `{key1}` doesn't work,
- # as Perl6 doesn't have barewords.
-```
-
-## Subs
-
-```perl6
-## Subroutines, or functions as most other languages call them, are
-## created with the `sub` keyword.
-sub say-hello { say "Hello, world" }
-
-## You can provide (typed) arguments. If specified, the type will be checked
-## at compile-time if possible, otherwise at runtime.
-sub say-hello-to( Str $name ) {
- say "Hello, $name !";
-}
-
-## A sub returns the last value of the block. Similarly, the semicolon in
-## the last can be omitted.
-sub return-value { 5 }
-say return-value; # prints 5
-
-sub return-empty { }
-say return-empty; # prints Nil
-
-## Some control flow structures produce a value, like `if`:
-sub return-if {
- if True { "Truthy" }
-}
-say return-if; # prints Truthy
-
-## Some don't, like `for`:
-sub return-for {
- for 1, 2, 3 { 'Hi' }
-}
-say return-for; # prints Nil
-
-## Positional arguments are required by default. To make them optional, use
-## the `?` after the parameters' names.
-sub with-optional( $arg? ) {
- # This sub returns `(Any)` (Perl's null-like value) if
- # no argument is passed. Otherwise, it returns its argument.
- $arg;
-}
-with-optional; # returns Any
-with-optional(); # returns Any
-with-optional(1); # returns 1
-
-## You can also give them a default value when they're not passed.
-## Required parameters must come before optional ones.
-sub greeting( $name, $type = "Hello" ) {
- say "$type, $name!";
-}
-
-greeting("Althea"); #=> Hello, Althea!
-greeting("Arthur", "Good morning"); #=> Good morning, Arthur!
-
-## You can also, by using a syntax akin to the one of hashes
-## (yay unified syntax !), pass *named* arguments to a `sub`. They're
-## optional, and will default to "Any".
-sub with-named( $normal-arg, :$named ) {
- say $normal-arg + $named;
-}
-with-named(1, named => 6); #=> 7
-
-## There's one gotcha to be aware of, here: If you quote your key, Perl 6
-## won't be able to see it at compile time, and you'll have a single `Pair`
-## object as a positional parameter, which means
-## `with-named(1, 'named' => 6);` fails.
-
-with-named(2, :named(5)); #=> 7
-
-## To make a named argument mandatory, you can append `!` to the parameter,
-## which is the inverse of `?`:
-sub with-mandatory-named( :$str! ) {
- say "$str!";
-}
-with-mandatory-named(str => "My String"); #=> My String!
-with-mandatory-named; # runtime error:"Required named parameter not passed"
-with-mandatory-named(3);# runtime error:"Too many positional parameters passed"
-
-## If a sub takes a named boolean argument...
-sub takes-a-bool( $name, :$bool ) {
- say "$name takes $bool";
-}
-## ... you can use the same "short boolean" hash syntax:
-takes-a-bool('config', :bool); #=> config takes True
-takes-a-bool('config', :!bool); #=> config takes False
-
-## You can also provide your named arguments with default values:
-sub named-def( :$def = 5 ) {
- say $def;
-}
-named-def; #=> 5
-named-def(def => 15); #=> 15
-
-## Since you can omit parenthesis to call a function with no arguments,
-## you need `&` in the name to store `say-hello` in a variable. This means
-## `&say-hello` is a code object and not a subroutine call.
-my &s = &say-hello;
-my &other-s = sub { say "Anonymous function!" }
-
-## A sub can have a "slurpy" parameter, or "doesn't-matter-how-many". For
-## this, you must use `*@` (slurpy) which will "take everything else". You can
-## have as many parameters *before* a slurpy one, but not *after*.
-sub as-many($head, *@rest) {
- say @rest.join(' / ') ~ " !";
-}
-say as-many('Happy', 'Happy', 'Birthday');#=> Happy / Birthday !
- # Note that the splat (the *) did not
- # consume the parameter before it.
-
-## You can call a function with an array using the "argument list flattening"
-## operator `|` (it's not actually the only role of this operator,
-## but it's one of them).
-sub concat3($a, $b, $c) {
- say "$a, $b, $c";
-}
-concat3(|@array); #=> a, b, c
- # `@array` got "flattened" as a part of the argument list
-```
-
-## Containers
-
-```perl6
-## In Perl 6, values are actually stored in "containers". The assignment
-## operator asks the container on the left to store the value on its right.
-## When passed around, containers are marked as immutable which means that,
-## in a function, you'll get an error if you try to mutate one of your
-## arguments. If you really need to, you can ask for a mutable container by
-## using the `is rw` trait:
-sub mutate( $n is rw ) {
- $n++; # postfix ++ operator increments its argument but returns its old value
-}
-
-my $m = 42;
-mutate $m; # the value is incremented but the old value is returned
- #=> 42
-say $m; #=> 43
-
-## This works because we are passing the container $m to the `mutate` sub.
-## If we try to just pass a number instead of passing a variable it won't work
-## because there is no container being passed and integers are immutable by
-## themselves:
-
-mutate 42; # Parameter '$n' expected a writable container, but got Int value
-
-## Similar error would be obtained, if a bound variable is passed to
-## to the subroutine:
-
-my $v := 50; # binding 50 to the variable $v
-mutate $v; # Parameter '$n' expected a writable container, but got Int value
-
-## If what you want is a copy instead, use the `is copy` trait which will
-## cause the argument to be copied and allow you to modify the argument
-## inside the routine.
-
-## A sub itself returns a container, which means it can be marked as rw:
-my $x = 42;
-sub x-store() is rw { $x }
-x-store() = 52; # in this case, the parentheses are mandatory
- # (else Perl 6 thinks `x-store` is an identifier)
-say $x; #=> 52
-```
-
-## Control Flow Structures
-
-### Conditionals
-
-```perl6
-## - `if`
-## Before talking about `if`, we need to know which values are "Truthy"
-## (represent True), and which are "Falsey" (represent False). Only these
-## values are Falsey: 0, (), {}, "", Nil, A type (like `Str` or `Int`) and
-## of course False itself. Any other value is Truthy.
-if True {
- say "It's true!";
-}
-
-unless False {
- say "It's not false!";
-}
-
-## As you can see, you don't need parentheses around conditions. However, you
-## do need the curly braces around the "body" block. For example,
-## `if (true) say;` doesn't work.
-
-## You can also use their statement modifier (postfix) versions:
-say "Quite truthy" if True; #=> Quite truthy
-say "Quite falsey" unless False; #=> Quite falsey
-
-## - Ternary operator, "x ?? y !! z"
-## This returns $value-if-true if the condition is true and $value-if-false
-## if it is false.
-## my $result = condition ?? $value-if-true !! $value-if-false;
-
-my $age = 30;
-say $age > 18 ?? "You are an adult" !! "You are under 18";
-#=> You are an adult
-```
-
-### given/when, or Perl 6's switch construct
-
-```perl6
-## `given...when` looks like other languages' `switch`, but is much more
-## powerful thanks to smart matching and Perl 6's "topic variable", $_.
-##
-## The topic variable $_ contains the default argument of a block, a loop's
-## current iteration (unless explicitly named), etc.
-##
-## `given` simply puts its argument into `$_` (like a block would do),
-## and `when` compares it using the "smart matching" (`~~`) operator.
-##
-## Since other Perl 6 constructs use this variable (as said before, like `for`,
-## blocks, etc), this means the powerful `when` is not only applicable along
-## with a `given`, but instead anywhere a `$_` exists.
-
-given "foo bar" {
- say $_; #=> foo bar
- when /foo/ { # Don't worry about smart matching yet. Just know
- say "Yay !"; # `when` uses it. This is equivalent to `if $_ ~~ /foo/`.
-
- }
- when $_.chars > 50 { # smart matching anything with True is True,
- # i.e. (`$a ~~ True`)
- # so you can also put "normal" conditionals.
- # This `when` is equivalent to this `if`:
- # `if $_ ~~ ($_.chars > 50) {...}`
- # which means: `if $_.chars > 50 {...}`
- say "Quite a long string !";
- }
- default { # same as `when *` (using the Whatever Star)
- say "Something else"
- }
-}
-```
-
-### Looping constructs
-
-```perl6
-## - `loop` is an infinite loop if you don't pass it arguments, but can also
-## be a C-style `for` loop:
-loop {
- say "This is an infinite loop !";
- last; # last breaks out of the loop, like
- # the `break` keyword in other languages
-}
-
-loop (my $i = 0; $i < 5; $i++) {
- next if $i == 3; # `next` skips to the next iteration, like `continue`
- # in other languages. Note that you can also use postfix
- # conditionals, loops, etc.
- say "This is a C-style for loop!";
-}
-
-## - `for` - Iterating through an array
-
-my @array = 1, 2, 6, 7, 3;
-
-## Accessing the array's elements with the topic variable $_.
-for @array {
- say "I've got $_ !";
-}
-
-## Accessing the array's elements with a "pointy block", `->`.
-## Here each element is read-only.
-for @array -> $variable {
- say "I've got $variable !";
-}
-
-## Accessing the array's elements with a "doubly pointy block", `<->`.
-## Here each element is read-write so mutating `$variable` mutates
-## that element in the array.
-for @array <-> $variable {
- say "I've got $variable !";
-}
-
-## As we saw with given, a for loop's default "current iteration" variable
-## is `$_`. That means you can use `when` in a `for`loop just like you were
-## able to in a `given`.
-for @array {
- say "I've got $_";
-
- .say; # This is also allowed. A dot call with no "topic" (receiver)
- # is sent to `$_` by default
- $_.say; # This is equivalent to the above statement.
-}
-
-for @array {
- # You can...
- next if $_ == 3; # Skip to the next iteration (`continue` in C-like lang.)
- redo if $_ == 4; # Re-do iteration, keeping the same topic variable (`$_`)
- last if $_ == 5; # Or break out of loop (like `break` in C-like lang.)
-}
-
-## The "pointy block" syntax isn't specific to the `for` loop. It's just a way
-## to express a block in Perl 6.
-sub long-computation { "Finding factors of large primes" }
-if long-computation() -> $result {
- say "The result is $result.";
-}
-```
-
-## Operators
-
-```perl6
-## Since Perl languages are very much operator-based languages, Perl 6
-## operators are actually just funny-looking subroutines, in syntactic
-## categories, like infix:<+> (addition) or prefix:<!> (bool not).
-
-## The categories are:
-## - "prefix": before (like `!` in `!True`).
-## - "postfix": after (like `++` in `$a++`).
-## - "infix": in between (like `*` in `4 * 3`).
-## - "circumfix": around (like `[`-`]` in `[1, 2]`).
-## - "post-circumfix": around, after another term (like `{`-`}` in
-## `%hash{'key'}`)
-
-## The associativity and precedence list are explained below.
-
-## Alright, you're set to go!
-
-## Equality Checking
-##------------------
-
-## - `==` is numeric comparison
-3 == 4; #=> False
-3 != 4; #=> True
-
-## - `eq` is string comparison
-'a' eq 'b'; #=> False
-'a' ne 'b'; #=> True, not equal
-'a' !eq 'b'; #=> True, same as above
-
-## - `eqv` is canonical equivalence (or "deep equality")
-(1, 2) eqv (1, 3); #=> False
-(1, 2) eqv (1, 2); #=> True
-Int === Int #=> True
-
-## - `~~` is the smart match operator
-## Aliases the left hand side to $_ and then evaluates the right hand side.
-## Here are some common comparison semantics:
-
-## String or numeric equality
-'Foo' ~~ 'Foo'; # True if strings are equal.
-12.5 ~~ 12.50; # True if numbers are equal.
-
-## Regex - For matching a regular expression against the left side.
-## Returns a `Match` object, which evaluates as True if regexp matches.
-
-my $obj = 'abc' ~~ /a/;
-say $obj; #=> 「a」
-say $obj.WHAT; #=> (Match)
-
-## Hashes
-'key' ~~ %hash; # True if key exists in hash.
-
-## Type - Checks if left side "is of type" (can check superclasses and
-## roles).
-say 1 ~~ Int; #=> True
-
-## Smart-matching against a boolean always returns that boolean
-## (and will warn).
-say 1 ~~ True; #=> True
-say False ~~ True; #=> True
-
-## General syntax is `$arg ~~ &bool-returning-function;`. For a complete list
-## of combinations, use this table:
-## http://perlcabal.org/syn/S03.html#Smart_matching
-
-## Of course, you also use `<`, `<=`, `>`, `>=` for numeric comparison.
-## Their string equivalent are also available: `lt`, `le`, `gt`, `ge`.
-3 > 4; # False
-3 >= 4; # False
-3 < 4; # True
-3 <= 4; # True
-'a' gt 'b'; # False
-'a' ge 'b'; # False
-'a' lt 'b'; # True
-'a' le 'b'; # True
-
-
-## Range constructor
-##------------------
-3 .. 7; # 3 to 7, both included.
-3 ..^ 7; # 3 to 7, exclude right endpoint.
-3 ^.. 7; # 3 to 7, exclude left endpoint.
-3 ^..^ 7; # 3 to 7, exclude both endpoints.
- # 3 ^.. 7 almost like 4 .. 7 when we only consider integers.
- # But when we consider decimals :
-3.5 ~~ 4 .. 7; # False
-3.5 ~~ 3 ^.. 7; # True, This Range also contains decimals greater than 3.
- # We describe it like this in some math books: 3.5 ∈ (3,7]
- # If you don’t want to understand the concept of interval
- # for the time being. At least we should know:
-3 ^.. 7 ~~ 4 .. 7; # False
-
-
-## This also works as a shortcut for `0..^N`:
-^10; # means 0..^10
-
-## This also allows us to demonstrate that Perl 6 has lazy/infinite arrays,
-## using the Whatever Star:
-my @array = 1..*; # 1 to Infinite! Equivalent to `1..Inf`.
-say @array[^10]; # You can pass ranges as subscripts and it'll return
- # an array of results. This will print
- # "1 2 3 4 5 6 7 8 9 10" (and not run out of memory!)
-
-## Note: when reading an infinite list, Perl 6 will "reify" the elements
-## it needs, then keep them in memory. They won't be calculated more than once.
-## It also will never calculate more elements that are needed.
-
-## An array subscript can also be a closure. It'll be called with the length
-## as the argument:
-say join(' ', @array[15..*]); #=> 15 16 17 18 19
-## which is equivalent to:
-say join(' ', @array[-> $n { 15..$n }]);
-
-## Note: if you try to do either of those with an infinite array,
-## you'll trigger an infinite loop (your program won't finish).
-
-## You can use that in most places you'd expect, even when assigning to
-## an array:
-my @numbers = ^20;
-
-## Here the numbers increase by 6, like an arithmetic sequence; more on the
-## sequence (`...`) operator later.
-my @seq = 3, 9 ... * > 95; # 3 9 15 21 27 [...] 81 87 93 99;
-@numbers[5..*] = 3, 9 ... *; # even though the sequence is infinite,
- # only the 15 needed values will be calculated.
-say @numbers; #=> 0 1 2 3 4 3 9 15 21 [...] 81 87
- # (only 20 values)
-
-## and (&&), or (||)
-##------------------
-3 && 4; # 4, which is Truthy. Calls `.Bool` on both 3 and 4 and gets `True`
- # so it returns 4 since both are `True`.
-3 && 0; # 0
-0 && 4; # 0
-
-0 || False; # False. Calls `.Bool` on `0` and `False` which are both `False`
- # so it retusns `False` since both are `False`.
-
-## Short-circuit (and tight) versions of the above
-## Return the first argument that evaluates to False, or the last argument.
-
-my ( $a, $b, $c ) = 1, 0, 2;
-$a && $b && $c; # Returns 0, the first False value
-
-## || Returns the first argument that evaluates to True
-$b || $a; # 1
-
-## And because you're going to want them, you also have compound assignment
-## operators:
-$a *= 2; # multiply and assignment. Equivalent to $a = $a * 2;
-$b %%= 5; # divisible by and assignment. Equivalent to $b = $b %% 2;
-$c div= 3; # return divisor and assignment. Equivalent to $c = $c div 3;
-$d mod= 4; # return remainder and assignment. Equivalent to $d = $d mod 4;
-@array .= sort; # calls the `sort` method and assigns the result back
-```
-
-## More on subs!
-
-```perl6
-## As we said before, Perl 6 has *really* powerful subs. We're going
-## to see a few more key concepts that make them better than in any
-## other language :-).
-```
-
-### Unpacking!
-
-```perl6
-## Unpacking is the ability to "extract" arrays and keys
-## (AKA "destructuring"). It'll work in `my`s and in parameter lists.
-my ($f, $g) = 1, 2;
-say $f; #=> 1
-my ($, $, $h) = 1, 2, 3; # keep the non-interesting values anonymous (`$`)
-say $h; #=> 3
-
-my ($head, *@tail) = 1, 2, 3; # Yes, it's the same as with "slurpy subs"
-my (*@small) = 1;
-
-sub unpack_array( @array [$fst, $snd] ) {
- say "My first is $fst, my second is $snd! All in all, I'm @array[].";
- # (^ remember the `[]` to interpolate the array)
-}
-unpack_array(@tail); #=> My first is 2, my second is 3! All in all, I'm 2 3.
-
-
-## If you're not using the array itself, you can also keep it anonymous,
-## much like a scalar:
-sub first-of-array( @ [$fst] ) { $fst }
-first-of-array(@small); #=> 1
-first-of-array(@tail); # Error: "Too many positional parameters passed"
- # (which means the array is too big).
-
-## You can also use a slurp...
-sub slurp-in-array(@ [$fst, *@rest]) { # You could keep `*@rest` anonymous
- say $fst + @rest.elems; # `.elems` returns a list's length.
- # Here, `@rest` is `(3,)`, since `$fst`
- # holds the `2`.
-}
-slurp-in-array(@tail); #=> 3
-
-## You could even extract on a slurpy (but it's pretty useless ;-).)
-sub fst(*@ [$fst]) { # or simply: `sub fst($fst) { ... }`
- say $fst;
-}
-fst(1); #=> 1
-fst(1, 2); # errors with "Too many positional parameters passed"
-
-## You can also destructure hashes (and classes, which you'll learn about
-## later). The syntax is basically the same as
-## `%hash-name (:key($variable-to-store-value-in))`.
-## The hash can stay anonymous if you only need the values you extracted.
-sub key-of( % (:value($val), :qua($qua)) ) {
- say "Got val $val, $qua times.";
-}
-
-## Then call it with a hash. You need to keep the curly braces for it to be a
-## hash or use `%()` instead to indicate a hash is being passed.
-key-of({value => 'foo', qua => 1}); #=> Got val foo, 1 times.
-key-of(%(value => 'foo', qua => 1)); #=> Got val foo, 1 times.
-#key-of(%hash); # the same (for an equivalent `%hash`)
-
-## The last expression of a sub is returned automatically (though you may
-## indicate explicitly by using the `return` keyword, of course):
-sub next-index( $n ) {
- $n + 1;
-}
-my $new-n = next-index(3); # $new-n is now 4
-
-## This is true for everything, except for the looping constructs (due to
-## performance reasons): there's no reason to build a list if we're just going to
-## discard all the results. If you still want to build one, you can use the
-## `do` statement prefix or the `gather` prefix, which we'll see later:
-
-sub list-of( $n ) {
- do for ^$n { # note the range-to prefix operator `^` (`0..^N`)
- $_ # current loop iteration known as the "topic" variable
- }
-}
-my @list3 = list-of(3); #=> (0, 1, 2)
-```
-
-### lambdas (or anonymous subroutines)
-
-```perl6
-## You can create a lambda with `-> {}` ("pointy block") ,
-## `{}` ("block") or `sub {}`.
-
-my &lambda1 = -> $argument {
- "The argument passed to this lambda is $argument"
-}
-
-my &lambda2 = {
- "The argument passed to this lambda is $_"
-}
-
-my &lambda3 = sub ($argument) {
- "The argument passed to this lambda is $argument"
-}
-
-## `-> {}` and `{}` are pretty much the same thing, except that the former can
-## take arguments, and that the latter can be mistaken as a hash by the parser.
-
-## We can, for example, add 3 to each value of an array using the
-## `map` function with a lambda:
-my @arrayplus3 = map({ $_ + 3 }, @array); # $_ is the implicit argument
-
-## A sub (`sub {}`) has different semantics than a block (`{}` or `-> {}`):
-## A block doesn't have a "function context" (though it can have arguments),
-## which means that if you return from it, you're going to return from the
-## parent function. Compare:
-sub is-in( @array, $elem ) {
- # this will `return` out of the `is-in` sub once the condition evaluated
- ## to True, the loop won't be run anymore.
- map({ return True if $_ == $elem }, @array);
-}
-## with:
-sub truthy-array( @array ) {
- # this will produce an array of `True` and `False`:
- # (you can also say `anon sub` for "anonymous subroutine")
- map(sub ($i) { if $i { return True } else { return False } }, @array);
- # ^ the `return` only returns from the anonymous `sub`
-}
-
-## The `anon` declarator can be used to create an anonymous sub from a
-## regular subroutine. The regular sub knows its name but its symbol is
-## prevented from getting installed in the lexical scope, the method table
-## and everywhere else.
-
-my $anon-sum = anon sub summation(*@a) { [+] *@a }
-say $anon-sum.name; #=> summation
-say $anon-sum(2, 3, 5); #=> 10
-#say summation; #=> Error: Undeclared routine: ...
-
-## You can also use the "whatever star" to create an anonymous subroutine.
-## (it'll stop at the furthest operator in the current expression)
-my @arrayplus3 = map(*+3, @array); # `*+3` is the same as `{ $_ + 3 }`
-my @arrayplus3 = map(*+*+3, @array); # Same as `-> $a, $b { $a + $b + 3 }`
- # also `sub ($a, $b) { $a + $b + 3 }`
-say (*/2)(4); #=> 2
- # Immediately execute the function Whatever created.
-say ((*+3)/5)(5); #=> 1.6
- # It works even in parens!
-
-## But if you need to have more than one argument (`$_`) in a block (without
-## wanting to resort to `-> {}`), you can also use the implicit argument
-## syntax, `$^`:
-map({ $^a + $^b + 3 }, @array);
-# which is equivalent to the following which uses a `sub`:
-map(sub ($a, $b) { $a + $b + 3 }, @array);
-
-## The parameters `$^a`, `$^b`, etc. are known as placeholder parameters or
-## self-declared positional parameters. They're sorted lexicographically so
-## `{ $^b / $^a }` is equivalent `-> $a, $b { $b / $a }`.
-```
-
-### About types...
-
-```perl6
-## Perl 6 is gradually typed. This means you can specify the type of your
-## variables/arguments/return types, or you can omit the type annotations in
-## in which case they'll default to `Any`. Obviously you get access to a few
-## base types, like `Int` and `Str`. The constructs for declaring types are
-## "subset", "class", "role", etc. which you'll see later.
-
-## For now, let us examine "subset" which is a "sub-type" with additional
-## checks. For example, "a very big integer is an Int that's greater than 500".
-## You can specify the type you're subtyping (by default, `Any`), and add
-## additional checks with the `where` clause:
-subset VeryBigInteger of Int where * > 500;
-## Or the set of the whole numbers:
-subset WholeNumber of Int where * >= 0;
-```
-
-### Multiple Dispatch
-
-```perl6
-## Perl 6 can decide which variant of a `sub` to call based on the type of the
-## arguments, or on arbitrary preconditions, like with a type or `where`:
-
-## with types:
-multi sub sayit( Int $n ) { # note the `multi` keyword here
- say "Number: $n";
-}
-multi sayit( Str $s ) { # a multi is a `sub` by default
- say "String: $s";
-}
-sayit("foo"); #=> "String: foo"
-sayit(25); #=> "Number: 25"
-sayit(True); # fails at *compile time* with "calling 'sayit' will never
- # work with arguments of types ..."
-
-## with arbitrary preconditions (remember subsets?):
-multi is-big(Int $n where * > 50) { "Yes!" } # using a closure
-multi is-big(Int $n where {$_ > 50}) { "Yes!" } # similar to above
-multi is-big(Int $ where 10..50) { "Quite." } # Using smart-matching
- # (could use a regexp, etc)
-multi is-big(Int $) { "No" }
-
-subset Even of Int where * %% 2;
-multi odd-or-even(Even) { "Even" } # The main case using the type.
- # We don't name the argument.
-multi odd-or-even($) { "Odd" } # "everthing else" hence the $ variable
-
-## You can even dispatch based on the presence of positional and
-## named arguments:
-multi with-or-without-you($with) {
- say "I wish I could but I can't";
-}
-multi with-or-without-you(:$with) {
- say "I can live! Actually, I can't.";
-}
-multi with-or-without-you {
- say "Definitely can't live.";
-}
-
-## This is very, very useful for many purposes, like `MAIN` subs (covered
-## later), and even the language itself uses it in several places.
-##
-## - `is`, for example, is actually a `multi sub` named `trait_mod:<is>`,
-## and it works off that.
-## - `is rw`, is simply a dispatch to a function with this signature:
-## sub trait_mod:<is>(Routine $r, :$rw!) {}
-##
-## (commented out because running this would be a terrible idea!)
-```
-
-## Scoping
-
-```perl6
-## In Perl 6, unlike many scripting languages, (such as Python, Ruby, PHP),
-## you must declare your variables before using them. The `my` declarator
-## you have learned uses "lexical scoping". There are a few other declarators,
-## (`our`, `state`, ..., ) which we'll see later. This is called
-## "lexical scoping", where in inner blocks, you can access variables from
-## outer blocks.
-my $file_scoped = 'Foo';
-sub outer {
- my $outer_scoped = 'Bar';
- sub inner {
- say "$file_scoped $outer_scoped";
- }
- &inner; # return the function
-}
-outer()(); #=> 'Foo Bar'
-
-## As you can see, `$file_scoped` and `$outer_scoped` were captured.
-## But if we were to try and use `$outer_scoped` outside the `outer` sub,
-## the variable would be undefined (and you'd get a compile time error).
-```
-
-## Twigils
-
-```perl6
-## There are many special `twigils` (composed sigils) in Perl 6. Twigils
-## define the variables' scope.
-## The * and ? twigils work on standard variables:
-## * Dynamic variable
-## ? Compile-time variable
-## The ! and the . twigils are used with Perl 6's objects:
-## ! Attribute (instance attribute)
-## . Method (not really a variable)
-
-## `*` twigil: Dynamic Scope
-## These variables use the `*` twigil to mark dynamically-scoped variables.
-## Dynamically-scoped variables are looked up through the caller, not through
-## the outer scope.
-
-my $*dyn_scoped_1 = 1;
-my $*dyn_scoped_2 = 10;
-
-sub say_dyn {
- say "$*dyn_scoped_1 $*dyn_scoped_2";
-}
-
-sub call_say_dyn {
- my $*dyn_scoped_1 = 25; # Defines $*dyn_scoped_1 only for this sub.
- $*dyn_scoped_2 = 100; # Will change the value of the file scoped variable.
- say_dyn(); #=> 25 100, $*dyn_scoped 1 and 2 will be looked
- # for in the call.
- # It uses the value of $*dyn_scoped_1 from inside
- # this sub's lexical scope even though the blocks
- # aren't nested (they're call-nested).
-}
-say_dyn(); #=> 1 10
-call_say_dyn(); #=> 25 100
- # Uses $*dyn_scoped_1 as defined in call_say_dyn even though
- # we are calling it from outside.
-say_dyn(); #=> 1 100 We changed the value of $*dyn_scoped_2 in
- # call_say_dyn so now its value has changed.
-```
-
-## Object Model
-
-```perl6
-## To call a method on an object, add a dot followed by the method name:
-## `$object.method`
-
-## Classes are declared with the `class` keyword. Attributes are declared
-## with the `has` keyword, and methods declared with the `method` keyword.
-
-## Every attribute that is private uses the ! twigil. For example: `$!attr`.
-## Immutable public attributes use the `.` twigil which creates a read-only
-## method named after the attribute. In fact, declaring an attribute with `.`
-## is equivalent to declaring the same attribute with `!` and then creating
-## a read-only method with the attribute's name. However, this is done for us
-## by Perl 6 automatically. The easiest way to remember the `$.` twigil is
-## by comparing it to how methods are called.
-
-## Perl 6's object model ("SixModel") is very flexible, and allows you to
-## dynamically add methods, change semantics, etc... Unfortunately, these will
-## not all be covered here, and you should refer to:
-## https://docs.perl6.org/language/objects.html.
-
-class Human {
- has Str $.name; # `$.name` is immutable but with an accessor method.
- has Str $.bcountry; # Use `$!bcountry` to modify it inside the class.
- has Str $.ccountry is rw; # This attribute can be modified from outside.
- has Int $!age = 0; # A private attribute with default value.
-
- method birthday {
- $!age += 1; # Add a year to human's age
- }
-
- method get-age {
- return $!age;
- }
-
- # This method is private to the class. Note the `!` before the
- # method's name.
- method !do-decoration {
- return "$!name was born in $!bcountry and now lives in $!ccountry."
- }
-
- # This method is public, just like `birthday` and `get-age`.
- method get-info {
- self.do-decoration; # Invoking a method on `self` inside the class.
- # Use `self!priv-method` for private method.
- # Use `self.publ-method` for public method.
- }
-};
-
-## Create a new instance of Human class.
-## Note: you can't set private-attribute from here (more later on).
-my $person1 = Human.new(
- name => "Jord",
- bcountry = "Togo",
- ccountry => "Togo"
-);
-
-say $person1.name; #=> Jord
-say $person1.bcountry; #=> Togo
-say $person1.ccountry; #=> Togo
-
-
-# $person1.bcountry = "Mali"; # This fails, because the `has $.bcountry`
- # is immutable. Jord can't change his birthplace.
-$person1.ccountry = "France"; # This works because the `$.ccountry` is mutable
- # (`is rw`). Now Jord's current country is France.
-
-# Calling methods on the instance objects.
-$person1.birthday; #=> 1
-$person1.get-info; #=> Jord was born in Togo and now lives in France.
-$person1.do-decoration; # This fails since the method `do-decoration` is
- # private.
-```
-
-### Object Inheritance
-
-```perl6
-## Perl 6 also has inheritance (along with multiple inheritance). While
-## methods are inherited, submethods are not. Submethods are useful for
-## object construction and destruction tasks, such as BUILD, or methods that
-## must be overridden by subtypes. We will learn about BUILD later on.
-
-class Parent {
- has $.age;
- has $.name;
-
- # This submethod won't be inherited by the Child class.
- submethod favorite-color {
- say "My favorite color is Blue";
- }
-
- # This method is inherited
- method talk { say "Hi, my name is $!name" }
-}
-
-# Inheritance uses the `is` keyword
-class Child is Parent {
- method talk { say "Goo goo ga ga" }
- # This shadows Parent's `talk` method.
- # This child hasn't learned to speak yet!
-}
-
-my Parent $Richard .= new(age => 40, name => 'Richard');
-$Richard.favorite-color; #=> "My favorite color is Blue"
-$Richard.talk; #=> "Hi, my name is Richard"
-## $Richard is able to access the submethod and he knows how to say his name.
-
-my Child $Madison .= new(age => 1, name => 'Madison');
-$Madison.talk; #=> "Goo goo ga ga", due to the overridden method.
-# $Madison.favorite-color # does not work since it is not inherited.
-
-## When you use `my T $var`, `$var` starts off with `T` itself in it,
-## so you can call `new` on it.
-## (`.=` is just the dot-call and the assignment operator:
-## `$a .= b` is the same as `$a = $a.b`)
-## Also note that `BUILD` (the method called inside `new`)
-## will set parent's properties too, so you can pass `val => 5`.
-```
-
-### Roles, or Mixins
-
-```perl6
-## Roles are supported too (which are called Mixins in other languages)
-role PrintableVal {
- has $!counter = 0;
- method print {
- say $.val;
- }
-}
-
-## you "apply" a role (or mixin) with `does` keyword:
-class Item does PrintableVal {
- has $.val;
-
- ## When `does`-ed, a `role` literally "mixes in" the class:
- ## the methods and attributes are put together, which means a class
- ## can access the private attributes/methods of its roles (but
- ## not the inverse!):
- method access {
- say $!counter++;
- }
-
- ## However, this:
- ## method print {}
- ## is ONLY valid when `print` isn't a `multi` with the same dispatch.
- ## (this means a parent class can shadow a child class's `multi print() {}`,
- ## but it's an error if a role does)
-
- ## NOTE: You can use a role as a class (with `is ROLE`). In this case,
- ## methods will be shadowed, since the compiler will consider `ROLE`
- ## to be a class.
-}
-```
-
-## Exceptions
-
-```perl6
-## Exceptions are built on top of classes, in the package `X` (like `X::IO`).
-## In Perl6 exceptions are automatically 'thrown':
-open 'foo'; #=> Failed to open file foo: no such file or directory
-## It will also print out what line the error was thrown at
-## and other error info.
-
-## You can throw an exception using `die`:
-die 'Error!'; #=> Error!
-
-## Or more explicitly:
-X::AdHoc.new(payload => 'Error!').throw; #=> Error!
-
-## In Perl 6, `orelse` is similar to the `or` operator, except it only matches
-## undefined variables instead of anything evaluating as `False`.
-## Undefined values include: `Nil`, `Mu` and `Failure` as well as `Int`, `Str`
-## and other types that have not been initialized to any value yet.
-## You can check if something is defined or not using the defined method:
-my $uninitialized;
-say $uninitiazilzed.defined; #=> False
-
-## When using `orelse` it will disarm the exception and alias $_ to that
-## failure. This will prevent it to being automatically handled and printing
-## lots of scary error messages to the screen. We can use the `exception`
-## method on the `$_` variable to access the exception
-open 'foo' orelse say "Something happened {.exception}";
-
-## This also works:
-open 'foo' orelse say "Something happened $_"; #=> Something happened
- #=> Failed to open file foo: no such file or directory
-## Both of those above work but in case we get an object from the left side
-## that is not a failure we will probably get a warning. We see below how we
-## can use try` and `CATCH` to be more specific with the exceptions we catch.
-```
-
-### Using `try` and `CATCH`
-
-```perl6
-## By using `try` and `CATCH` you can contain and handle exceptions without
-## disrupting the rest of the program. The `try` block will set the last
-## exception to the special variable `$!` (known as the error variable).
-## Note: This has no relation to $!variables seen inside class definitions.
-
-try open 'foo';
-say "Well, I tried! $!" if defined $!;
-#=> Well, I tried! Failed to open file foo: no such file or directory
-
-## Now, what if we want more control over handling the exception?
-## Unlike many other languages, in Perl 6, you put the `CATCH` block *within*
-## the block to `try`. Similar to how the `$_` variable was set when we
-## 'disarmed' the exception with `orelse`, we also use `$_` in the CATCH block.
-## Note: The `$!` variable is only set *after* the `try` block has caught an
-## exception. By default, a `try` block has a `CATCH` block of its own that
-## catches any exception (`CATCH { default {} }`).
-
-try {
- my $a = (0 %% 0);
- CATCH {
- say "Something happened: $_"
- }
-}
-#=> Something happened: Attempt to divide by zero using infix:<%%>
-
-## You can redefine it using `when`s (and `default`) to handle the exceptions
-## you want to catch explicitly:
-
-try {
- open 'foo';
- CATCH {
- # In the `CATCH` block, the exception is set to the $_ variable.
- when X::AdHoc {
- say "Error: $_"
- }
- when X::Numeric::DivideByZero {
- say "Error: $_";
- }
- ## Any other exceptions will be re-raised, since we don't have a `default`.
- ## Basically, if a `when` matches (or there's a `default`), the
- ## exception is marked as "handled" so as to prevent its re-throw
- ## from the `CATCH` block. You still can re-throw the exception (see below)
- ## by hand.
- }
-}
-#=>Error: Failed to open file /dir/foo: no such file or directory
-
-## There are also some subtleties to exceptions. Some Perl 6 subs return a
-## `Failure`, which is a wrapper around an `Exception` object which is
-## "unthrown". They're not thrown until you try to use the variables containing
-## them unless you call `.Bool`/`.defined` on them - then they're handled.
-## (the `.handled` method is `rw`, so you can mark it as `False` back yourself)
-## You can throw a `Failure` using `fail`. Note that if the pragma `use fatal`
-## is on, `fail` will throw an exception (like `die`).
-
-fail "foo"; # We're not trying to access the value, so no problem.
-try {
- fail "foo";
- CATCH {
- default {
- say "It threw because we tried to get the fail's value!"
- }
- }
-}
-
-## There is also another kind of exception: Control exceptions.
-## Those are "good" exceptions, which happen when you change your program's
-## flow, using operators like `return`, `next` or `last`.
-## You can "catch" those with `CONTROL` (not 100% working in Rakudo yet).
-```
-
-## Packages
-
-```perl6
-## Packages are a way to reuse code. Packages are like "namespaces", and any
-## element of the six model (`module`, `role`, `class`, `grammar`, `subset` and
-## `enum`) are actually packages. (Packages are the lowest common denominator)
-## Packages are important - especially as Perl is well-known for CPAN,
-## the Comprehensive Perl Archive Network.
-
-## You can use a module (bring its declarations into scope) with
-## the `use` keyword:
-use JSON::Tiny; # if you installed Rakudo* or Panda, you'll have this module
-say from-json('[1]').perl; #=> [1]
-
-## You should not declare packages using the `package` keyword (unlike Perl 5).
-## Instead, use `class Package::Name::Here;` to declare a class, or if you only
-## want to export variables/subs, you can use `module` instead.
-
-module Hello::World { # bracketed form
- # If `Hello` doesn't exist yet, it'll just be a "stub",
- # that can be redeclared as something else later.
-
- # ... declarations here ...
-}
-
-unit module Parse::Text; # file-scoped form which extends until
- # the end of the file
-
-grammar Parse::Text::Grammar {
- # A grammar is a package, which you could `use`.
- # You will learn more about grammars in the regex section
-}
-
-## As said before, any part of the six model is also a package.
-## Since `JSON::Tiny` uses its own `JSON::Tiny::Actions` class, you can use it:
-my $actions = JSON::Tiny::Actions.new;
-
-## We'll see how to export variables and subs in the next part.
-```
-
-## Declarators
-
-```perl6
-## In Perl 6, you get different behaviors based on how you declare a variable.
-## You've already seen `my` and `has`, we'll now explore the others.
-
-## `our` - these declarations happen at `INIT` time -- (see "Phasers" below).
-## It's like `my`, but it also creates a package variable. All packagish
-## things such as `class`, `role`, etc. are `our` by default.
-
-module Var::Increment {
- our $our-var = 1; # Note: `our`-declared variables cannot be typed.
- my $my-var = 22;
-
- our sub Inc {
- our sub available { # If you try to make inner `sub`s `our`...
- # ... Better know what you're doing (Don't !).
- say "Don't do that. Seriously. You'll get burned.";
- }
-
- my sub unavailable { # `sub`s are `my`-declared by default
- say "Can't access me from outside, I'm 'my'!";
- }
- say ++$our-var; # Increment the package variable and output its value
- }
-
-}
-
-say $Var::Increment::our-var; #=> 1, this works!
-say $Var::Increment::my-var; #=> (Any), this will not work!
-
-Var::Increment::Inc; #=> 2
-Var::Increment::Inc; #=> 3 , notice how the value of $our-var was
- # retained.
-Var::Increment::unavailable; #=> Could not find symbol '&unavailable'
-
-## `constant` - these declarations happen at `BEGIN` time. You can use
-## the `constant` keyword to declare a compile-time variable/symbol:
-constant Pi = 3.14;
-constant $var = 1;
-
-## And if you're wondering, yes, it can also contain infinite lists.
-constant why-not = 5, 15 ... *;
-say why-not[^5]; #=> 5 15 25 35 45
-
-## `state` - these declarations happen at run time, but only once. State
-## variables are only initialized one time. In other languages such as C
-## they exist as `static` variables.
-sub fixed-rand {
- state $val = rand;
- say $val;
-}
-fixed-rand for ^10; # will print the same number 10 times
-
-## Note, however, that they exist separately in different enclosing contexts.
-## If you declare a function with a `state` within a loop, it'll re-create the
-## variable for each iteration of the loop. See:
-for ^5 -> $a {
- sub foo {
- state $val = rand; # This will be a different value for
- # every value of `$a`
- }
- for ^5 -> $b {
- say foo; # This will print the same value 5 times,
- # but only 5. Next iteration will re-run `rand`.
- }
-}
-```
-
-## Phasers
-
-```perl6
-## Phasers in Perl 6 are blocks that happen at determined points of time in
-## your program. They are called phasers because they mark a change in the
-## phase of a program. For example, when the program is compiled, a for loop
-## runs, you leave a block, or an exception gets thrown (The `CATCH` block is
-## actually a phaser!). Some of them can be used for their return values,
-## some of them can't (those that can have a "[*]" in the beginning of their
-## explanation text). Let's have a look!
-
-## Compile-time phasers
-BEGIN { say "[*] Runs at compile time, as soon as possible, only once" }
-CHECK { say "[*] Runs at compile time, as late as possible, only once" }
-
-## Run-time phasers
-INIT { say "[*] Runs at run time, as soon as possible, only once" }
-END { say "Runs at run time, as late as possible, only once" }
-
-## Block phasers
-ENTER { say "[*] Runs everytime you enter a block, repeats on loop blocks" }
-LEAVE {
- say "Runs everytime you leave a block, even when an exception
- happened. Repeats on loop blocks."
-}
-
-PRE {
- say "Asserts a precondition at every block entry,
- before ENTER (especially useful for loops)";
- say "If this block doesn't return a truthy value,
- an exception of type X::Phaser::PrePost is thrown.";
-}
-
-## Example:
-for 0..2 {
- PRE { $_ > 1 } # This is going to blow up with "Precondition failed"
-}
-
-POST {
- say "Asserts a postcondition at every block exit,
- after LEAVE (especially useful for loops)";
- say "If this block doesn't return a truthy value,
- an exception of type X::Phaser::PrePost is thrown, like PRE.";
-}
-
-for 0..2 {
- POST { $_ < 2 } # This is going to blow up with "Postcondition failed"
-}
-
-## Block/exceptions phasers
-sub {
- KEEP { say "Runs when you exit a block successfully
- (without throwing an exception)" }
- UNDO { say "Runs when you exit a block unsuccessfully
- (by throwing an exception)" }
-}
-
-## Loop phasers
-for ^5 {
- FIRST { say "[*] The first time the loop is run, before ENTER" }
- NEXT { say "At loop continuation time, before LEAVE" }
- LAST { say "At loop termination time, after LEAVE" }
-}
-
-## Role/class phasers
-COMPOSE { "When a role is composed into a class. /!\ NOT YET IMPLEMENTED" }
-
-## They allow for cute tricks or clever code...:
-say "This code took " ~ (time - CHECK time) ~ "s to compile";
-
-## ... or clever organization:
-sub do-db-stuff {
- $db.start-transaction; # start a new transaction
- KEEP $db.commit; # commit the transaction if all went well
- UNDO $db.rollback; # or rollback if all hell broke loose
-}
-```
-
-## Statement prefixes
-
-```perl6
-## Those act a bit like phasers: they affect the behavior of the following
-## code. Though, they run in-line with the executable code, so they're in
-## lowercase. (`try` and `start` are theoretically in that list, but explained
-## elsewhere) Note: all of these (except start) don't need explicit curly
-## braces `{` and `}`.
-
-## `do` - (which you already saw) runs a block or a statement as a term.
-## Normally you cannot use a statement as a value (or "term"). `do` helps us
-## do it.
-
-# my $value = if True { 1 } # this fails since `if` is a statement
-my $a = do if True { 5 } # with `do`, `if` is now a term returning a value
-
-## `once` - makes sure a piece of code only runs once.
-for ^5 {
- once say 1
-}; #=> 1, only prints ... once
-
-## Similar to `state`, they're cloned per-scope.
-for ^5 {
- sub { once say 1 }()
-}; #=> 1 1 1 1 1, prints once per lexical scope.
-
-## `gather` - co-routine thread. The `gather` constructs allows us to `take`
-## several values from an array/list, much like `do`.
-say gather for ^5 {
- take $_ * 3 - 1;
- take $_ * 3 + 1;
-}
-#=> -1 1 2 4 5 7 8 10 11 13
-
-say join ',', gather if False {
- take 1;
- take 2;
- take 3;
-}
-# Doesn't print anything.
-
-## `eager` - evaluates a statement eagerly (forces eager context)
-## Don't try this at home:
-# eager 1..*; # this will probably hang for a while (and might crash ...).
-## But consider:
-constant thrice = gather for ^3 { say take $_ }; # Doesn't print anything
-## versus:
-constant thrice = eager gather for ^3 { say take $_ }; #=> 0 1 2
-```
-
-## Iterables
-
-```perl6
-## Iterables are objects that can be iterated over which are
-## are similar to the `for` construct.
-
-## `flat` - flattens iterables.
-say (1, 10, (20, 10) ); #=> (1 10 (20 10)), notice how neste lists are
- # preserved
-say (1, 10, (20, 10) ).flat; #=> (1 10 20 10), now the iterable is flat
-
-## - `lazy` - defers actual evaluation until value is fetched by forcing
-## lazy context.
-my @lazy-array = (1..100).lazy;
-say @lazy-array.is-lazy; #=> True, check for laziness with the `is-lazy` method.
-say @lazy-array; #=> [...] List has not been iterated on!
-my @lazy-array { .print }; # This works and will only do as much work as
- # is needed.
-
-# ( **TODO** explain that gather/take and map are all lazy)
-
-## `sink` - an `eager` that discards the results by forcing sink context.
-constant nilthingie = sink for ^3 { .say } #=> 0 1 2
-say nilthingie.perl; #=> Nil
-
-## `quietly` - suppresses warnings in blocks.
-quietly { warn 'This is a warning!' }; #=> No output
-
-## `contend` - attempts side effects under STM
-## Not yet implemented!
-```
-
-## More operators thingies!
-
-```perl6
-## Everybody loves operators! Let's get more of them.
-
-## The precedence list can be found here:
-## https://docs.perl6.org/language/operators#Operator_Precedence
-## But first, we need a little explanation about associativity:
-
-## Binary operators:
-$a ! $b ! $c; # with a left-associative `!`, this is `($a ! $b) ! $c`
-$a ! $b ! $c; # with a right-associative `!`, this is `$a ! ($b ! $c)`
-$a ! $b ! $c; # with a non-associative `!`, this is illegal
-$a ! $b ! $c; # with a chain-associative `!`, this is `($a ! $b) and ($b ! $c)`
-$a ! $b ! $c; # with a list-associative `!`, this is `infix:<>`
-
-## Unary operators:
-!$a! # with left-associative `!`, this is `(!$a)!`
-!$a! # with right-associative `!`, this is `!($a!)`
-!$a! # with non-associative `!`, this is illegal
-```
-
-### Create your own operators!
-
-```perl6
-## Okay, you've been reading all of that, so you might want to try something
-## more exciting?! I'll tell you a little secret (or not-so-secret):
-## In Perl 6, all operators are actually just funny-looking subroutines.
-
-## You can declare an operator just like you declare a sub:
-# prefix refers to the operator categories (prefix, infix, postfix, etc).
-sub prefix:<win>( $winner ) {
- say "$winner Won!";
-}
-win "The King"; #=> The King Won!
- # (prefix means 'before')
-
-## you can still call the sub with its "full name":
-say prefix:<!>(True); #=> False
-prefix:<win>("The Queen"); #=> The Queen Won!
-
-sub postfix:<!>( Int $n ) {
- [*] 2..$n; # using the reduce meta-operator... See below ;-)!
-}
-say 5!; #=> 120
- # Postfix operators ('after') have to come *directly* after the term.
- # No whitespace. You can use parentheses to disambiguate, i.e. `(5!)!`
-
-sub infix:<times>( Int $n, Block $r ) { # infix ('between')
- for ^$n {
- $r(); # You need the explicit parentheses to call the function in `$r`,
- # else you'd be referring at the variable itself, like with `&r`.
- }
-}
-3 times -> { say "hello" }; #=> hello
- #=> hello
- #=> hello
-## It's recommended to put spaces around your
-## infix operator calls.
-
-## For circumfix and post-circumfix ones
-sub circumfix:<[ ]>( Int $n ) {
- $n ** $n
-}
-say [5]; #=> 3125
- # circumfix means 'around'. Again, no whitespace.
-
-sub postcircumfix:<{ }>( Str $s, Int $idx ) {
- ## post-circumfix is 'after a term, around something'
- $s.substr($idx, 1);
-}
-say "abc"{1}; #=> b
- # after the term `"abc"`, and around the index (1)
-
-## This really means a lot -- because everything in Perl 6 uses this.
-## For example, to delete a key from a hash, you use the `:delete` adverb
-## (a simple named argument underneath):
-%h{$key}:delete;
-## equivalent to:
-postcircumfix:<{ }>( %h, $key, :delete ); # (you can call operators like this)
-
-## It's *all* using the same building blocks! Syntactic categories
-## (prefix infix ...), named arguments (adverbs), ..., etc. used to build
-## the language - are available to you. Obviously, you're advised against
-## making an operator out of *everything* -- with great power comes great
-## responsibility.
-```
-
-### Meta operators!
-
-```perl6
-## Oh boy, get ready!. Get ready, because we're delving deep into the rabbit's
-## hole, and you probably won't want to go back to other languages after
-## reading this. (I'm guessing you don't want to go back at this point but
-## let's continue, for the journey is long and enjoyable!).
-
-## Meta-operators, as their name suggests, are *composed* operators.
-## Basically, they're operators that act on another operators.
-
-## The reduce meta-operator is a prefix meta-operator that takes a binary
-## function and one or many lists. If it doesn't get passed any argument,
-## it either returns a "default value" for this operator (a meaningless value)
-## or `Any` if there's none (examples below). Otherwise, it pops an element
-## from the list(s) one at a time, and applies the binary function to the last
-## result (or the list's first element) and the popped element.
-
-## To sum a list, you could use the reduce meta-operator with `+`, i.e.:
-say [+] 1, 2, 3; #=> 6, equivalent to (1+2)+3.
-
-## To multiply a list
-say [*] 1..5; #=> 120, equivalent to ((((1*2)*3)*4)*5).
-
-## You can reduce with any operator, not just with mathematical ones.
-## For example, you could reduce with `//` to get first defined element
-## of a list:
-say [//] Nil, Any, False, 1, 5; #=> False
- # (Falsey, but still defined)
-## Or with relational operators, i.e., `>` to check elements of a list
-## are ordered accordingly:
-say say [>] 234, 156, 6, 3, -20; #=> True
-
-## Default value examples:
-say [*] (); #=> 1
-say [+] (); #=> 0
- # meaningless values, since N*1=N and N+0=N.
-say [//]; #=> (Any)
- # There's no "default value" for `//`.
-
-## You can also call it with a function you made up, using double brackets:
-sub add($a, $b) { $a + $b }
-say [[&add]] 1, 2, 3; #=> 6
-
-## The zip meta-operator is an infix meta-operator that also can be used as a
-## "normal" operator. It takes an optional binary function (by default, it
-## just creates a pair), and will pop one value off of each array and call
-## its binary function on these until it runs out of elements. It returns an
-## array with all of these new elements.
-say (1, 2) Z (3, 4); #=> ((1, 3), (2, 4)), since by default the function
- # makes an array.
-say 1..3 Z+ 4..6; #=> (5, 7, 9), using the custom infix:<+> function
-
-## Since `Z` is list-associative (see the list above),
-## you can use it on more than one list
-(True, False) Z|| (False, False) Z|| (False, False); # (True, False)
-
-## And, as it turns out, you can also use the reduce meta-operator with it:
-[Z||] (True, False), (False, False), (False, False); # (True, False)
-
-
-## And to end the operator list:
-
-## The sequence operator is one of Perl 6's most powerful features:
-## it's composed of first, on the left, the list you want Perl 6 to deduce from
-## (and might include a closure), and on the right, a value or the predicate
-## that says when to stop (or a Whatever Star for a lazy infinite list).
-
-my @list = 1, 2, 3...10; # basic arithmetic sequence
-# my @list = 1, 3, 6...10; # this dies because Perl 6 can't figure out the end
-my @list = 1, 2, 3...^10; # as with ranges, you can exclude the last element
- # (the iteration ends when the predicate matches).
-my @list = 1, 3, 9...* > 30; # you can use a predicate (with the Whatever Star).
-my @list = 1, 3, 9 ... { $_ > 30 }; # (equivalent to the above
- # using a block here).
-
-my @fib = 1, 1, *+* ... *; # lazy infinite list of fibonacci sequence,
- # computed using a closure!
-my @fib = 1, 1, -> $a, $b { $a + $b } ... *; # (equivalent to the above)
-my @fib = 1, 1, { $^a + $^b } ... *; # (also equivalent to the above)
-## $a and $b will always take the previous values, meaning here
-## they'll start with $a = 1 and $b = 1 (values we set by hand),
-## then $a = 1 and $b = 2 (result from previous $a+$b), and so on.
-
-say @fib[^10]; #=> 1 1 2 3 5 8 13 21 34 55
- # (using a range as the index)
-## Note: as for ranges, once reified, elements aren't re-calculated.
-## That's why `@primes[^100]` will take a long time the first time you print
-## it, then will be instateneous.
-```
-
-## Regular Expressions
-
-```perl6
-## I'm sure a lot of you have been waiting for this one. Well, now that you know
-## a good deal of Perl 6 already, we can get started. First off, you'll have to
-## forget about "PCRE regexps" (perl-compatible regexps).
-##
-## IMPORTANT: Don't skip them because you know PCRE. They're different. Some
-## things are the same (like `?`, `+`, and `*`), but sometimes the semantics
-## change (`|`). Make sure you read carefully, because you might trip over a
-## new behavior.
-##
-## Perl 6 has many features related to RegExps. After all, Rakudo parses itself.
-## We're first going to look at the syntax itself, then talk about grammars
-## (PEG-like), differences between `token`, `regex` and `rule` declarators,
-## and some more. Side note: you still have access to PCRE regexps using the
-## `:P5` modifier which we won't be discussing this in this tutorial, though.
-##
-## In essence, Perl 6 natively implements PEG ("Parsing Expression Grammars").
-## The pecking order for ambiguous parses is determined by a multi-level
-## tie-breaking test:
-## - Longest token matching: `foo\s+` beats `foo` (by 2 or more positions)
-## - Longest literal prefix: `food\w*` beats `foo\w*` (by 1)
-## - Declaration from most-derived to less derived grammars
-## (grammars are actually classes)
-## - Earliest declaration wins
-say so 'a' ~~ /a/; #=> True
-say so 'a' ~~ / a /; #=> True, more readable with some spaces!
-
-## In all our examples, we're going to use the smart-matching operator against
-## a regexp. We're converting the result using `so` to a Boolean value because,
-## in fact, it's returning a `Match` object. They know how to respond to list
-## indexing, hash indexing, and return the matched string. The results of the
-## match are available in the `$/` variable (implicitly lexically-scoped). You
-## can also use the capture variables which start at 0: `$0`, `$1', `$2`...
-##
-## You can also note that `~~` does not perform start/end checking, meaning
-## the regexp can be matched with just one character of the string. We'll
-## explain later how you can do it.
-
-## In Perl 6, you can have any alphanumeric as a literal, everything else has
-## to be escaped by using a backslash or quotes.
-say so 'a|b' ~~ / a '|' b /; #=> `True`, it wouldn't mean the same thing if
- # `|` wasn't escaped.
-say so 'a|b' ~~ / a \| b /; #=> `True`, another way to escape it.
-
-## The whitespace in a regexp is actually not significant, unless you use the
-## `:s` (`:sigspace`, significant space) adverb.
-say so 'a b c' ~~ / a b c /; #=> `False`, space is not significant here!
-say so 'a b c' ~~ /:s a b c /; #=> `True`, we added the modifier `:s` here.
-
-## If we use only one space between strings in a regex, Perl 6 will warn us:
-say so 'a b c' ~~ / a b c /; #=> `False`, with warning about space
-say so 'a b c' ~~ / a b c /; #=> `False`
-
-## Please use quotes or :s (:sigspace) modifier (or, to suppress this warning,
-## omit the space, or otherwise change the spacing). To fix this and make the
-## spaces less ambiguous, either use at least two spaces between strings
-## or use the `:s` adverb.
-
-## As we saw before, we can embed the `:s` inside the slash delimiters, but we
-## can also put it outside of them if we specify `m` for 'match':
-say so 'a b c' ~~ m:s/a b c/; #=> `True`
-
-## By using `m` to specify 'match', we can also use delimiters other than
-## slashes:
-say so 'abc' ~~ m{a b c}; #=> `True`
-say so 'abc' ~~ m[a b c]; #=> `True`
-# m/.../ is equivalent to /.../
-
-## Use the :i adverb to specify case insensitivity:
-say so 'ABC' ~~ m:i{a b c}; #=> `True`
-
-## However, whitespace is important as for how modifiers are applied (
-## (which you'll see just below) ...
-
-## Quantifying - `?`, `+`, `*` and `**`.
-## `?` - zero or one match
-so 'ac' ~~ / a b c /; #=> `False`
-so 'ac' ~~ / a b? c /; #=> `True`, the "b" matched 0 times.
-so 'abc' ~~ / a b? c /; #=> `True`, the "b" matched 1 time.
-
-## ...As you read before, whitespace is important because it determines which
-## part of the regexp is the target of the modifier:
-so 'def' ~~ / a b c? /; #=> `False`, only the `c` is optional
-so 'def' ~~ / a b? c /; #=> `False`, whitespace is not significant
-so 'def' ~~ / 'abc'? /; #=> `True`, the whole "abc" group is optional
-
-## Here (and below) the quantifier applies only to the `b`
-
-## `+` - one or more matches
-so 'ac' ~~ / a b+ c /; #=> `False`, `+` wants at least one matching
-so 'abc' ~~ / a b+ c /; #=> `True`, one is enough
-so 'abbbbc' ~~ / a b+ c /; #=> `True`, matched 4 "b"s
-
-## `*` - zero or more matches
-so 'ac' ~~ / a b* c /; #=> `True`, they're all optional.
-so 'abc' ~~ / a b* c /; #=> `True`
-so 'abbbbc' ~~ / a b* c /; #=> `True`
-so 'aec' ~~ / a b* c /; #=> `False`. "b"(s) are optional, not replaceable.
-
-## `**` - (Unbound) Quantifier
-## If you squint hard enough, you might understand why exponentation is used
-## for quantity.
-so 'abc' ~~ / a b**1 c /; #=> `True`, (exactly one time)
-so 'abc' ~~ / a b**1..3 c /; #=> `True`, (one to three times)
-so 'abbbc' ~~ / a b**1..3 c /; #=> `True`
-so 'abbbbbbc' ~~ / a b**1..3 c /; #=> `False, (too much)
-so 'abbbbbbc' ~~ / a b**3..* c /; #=> `True`, (infinite ranges are okay)
-
-## `<[]>` - Character classes
-## Character classes are the equivalent of PCRE's `[]` classes, but they use a
-## more perl6-ish syntax:
-say 'fooa' ~~ / f <[ o a ]>+ /; #=> 'fooa'
-
-## You can use ranges:
-say 'aeiou' ~~ / a <[ e..w ]> /; #=> 'ae'
-
-## Just like in normal regexes, if you want to use a special character, escape
-## it (the last one is escaping a space which would be equivalent to using
-## ' '):
-say 'he-he !' ~~ / 'he-' <[ a..z \! \ ]> + /; #=> 'he-he !'
-
-## You'll get a warning if you put duplicate names (which has the nice effect
-## of catching the raw quoting):
-'he he' ~~ / <[ h e ' ' ]> /;
-# Warns "Repeated character (') unexpectedly found in character class"
-
-## You can also negate character classes... (`<-[]>` equivalent to `[^]` in PCRE)
-so 'foo' ~~ / <-[ f o ]> + /; #=> False
-
-## ... and compose them:
-so 'foo' ~~ / <[ a..z ] - [ f o ]> + /; #=> `False`, (any letter except f and o)
-so 'foo' ~~ / <-[ a..z ] + [ f o ]> + /; #=> `True`, (no letter except f and o)
-so 'foo!' ~~ / <-[ a..z ] + [ f o ]> + /; #=> `True`, (the + doesn't replace the
- # left part)
-```
-
-### Grouping and capturing
-
-```perl6
-## Group: you can group parts of your regexp with `[]`. Unlike PCRE's `(?:)`,
-## these groups are *not* captured.
-so 'abc' ~~ / a [ b ] c /; # `True`. The grouping does pretty much nothing
-so 'foo012012bar' ~~ / foo [ '01' <[0..9]> ] + bar /;
-
-## The previous line returns `True`. The regex matches "012" 1 or more time
-## (achieved by the the `+` applied to the group).
-
-## But this does not go far enough, because we can't actually get back what
-## we matched.
-
-## Capture: The results of a regexp can be *captured* by using parentheses.
-so 'fooABCABCbar' ~~ / foo ( 'A' <[A..Z]> 'C' ) + bar /; # `True`. (using `so`
- # here, `$/` below)
-
-## So, starting with the grouping explanations.
-## As we said before, our `Match` object is stored inside the `$/` variable:
-say $/; # Will either print some weird stuff or `Nil` if nothing matched.
-
-## As we also said before, it has array indexing:
-say $/[0]; #=> 「ABC」 「ABC」
- # These corner brackets are `Match` objects.
- # Here, we have an array of these.
-say $0; # The same as above.
-
-## Our capture is `$0` because it's the first and only one capture in the
-## regexp. You might be wondering why it's an array, and the answer is simple:
-## Some captures (indexed using `$0`, `$/[0]` or a named one) will be an array
-## if and only if they can have more than one element. Thus any capture with
-## `*`, `+` and `**` (whatever the operands), but not with `?`.
-## Let's use examples to see that:
-
-## Note: We quoted A B C to demonstrate that the whitespace between them isn't
-## significant. If we want the whitespace to *be* significant there, we
-## can use the :sigspace modifier.
-say so 'fooABCbar' ~~ / foo ( "A" "B" "C" )? bar /; #=> `True`
-say $/[0]; #=> 「ABC」
-say $0.WHAT; #=> (Match)
- # There can't be more than one, so it's only a single match object.
-say so 'foobar' ~~ / foo ( "A" "B" "C" )? bar /; #=> True
-say $0.WHAT; #=> (Any)
- # This capture did not match, so it's empty
-so 'foobar' ~~ / foo ( "A" "B" "C" ) ** 0..1 bar /; #=> `True`
-say $0.WHAT; #=> (Array)
- # A specific quantifier will always capture an Array,
- # be a range or a specific value (even 1).
-
-## The captures are indexed per nesting. This means a group in a group will be
-## nested under its parent group: `$/[0][0]`, for this code:
-'hello-~-world' ~~ / ( 'hello' ( <[ \- \~ ]> + ) ) 'world' /;
-say $/[0].Str; #=> hello~
-say $/[0][0].Str; #=> ~
-
-## This stems from a very simple fact: `$/` does not contain strings, integers
-## or arrays, it only contains Match objects. These contain the `.list`, `.hash`
-## and `.Str` methods but you can also just use `match<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. These contain
- # a bunch of info: where the match started/ended,
- # the "ast" (see actions later), etc.
- # You'll see named capture below with grammars.
-
-## Alternation - the `or` of regexps
-## WARNING: They are DIFFERENT from PCRE regexps.
-say so 'abc' ~~ / a [ b | y ] c /; #=> `True`. Either "b" or "y".
-say so 'ayc' ~~ / a [ b | y ] c /; #=> `True`. Obviously enough...
-
-## The difference between this `|` and the one you're used to is
-## LTM ("Longest Token Matching"). This means that the engine will always
-## try to match as much as possible in the string.
-say 'foo' ~~ / fo | foo /; #=> `foo`, instead of `fo`, because it's longer.
-
-## To decide which part is the "longest", it first splits the regex in
-## two parts:
-## The "declarative prefix" (the part that can be statically analyzed)
-## and the procedural parts:
-## - The declarative prefixes include alternations (`|`), conjunctions (`&`),
-## sub-rule calls (not yet introduced), literals, characters classes and
-## quantifiers.
-## - The procedural part include everything else: back-references,
-## code assertions, and other things that can't traditionnaly be represented
-## by normal regexps.
-##
-## Then, all the alternatives are tried at once, and the longest wins.
-## Examples:
-## DECLARATIVE | PROCEDURAL
-/ 'foo' \d+ [ <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 `||`
-say 'foo' ~~ / fo || foo /; #=> `fo` now.
-```
-
-## Extra: the MAIN subroutine
-
-```perl6
-## The `MAIN` subroutine is called when you run a Perl 6 file directly. It's
-## very powerful, because Perl 6 actually parses the arguments and pass them
-## as such to the sub. It also handles named argument (`--foo`) and will even
-## go as far as to autogenerate a `--help` flag.
-sub MAIN($name) {
- say "Hello, $name!";
-}
-## This produces:
-## $ perl6 cli.pl
-## Usage:
-## t.pl <name>
-
-## And since it's a regular Perl 6 sub, you can have multi-dispatch:
-## (using a "Bool" for the named argument so that we can do `--replace`
-## instead of `--replace=1`. The presence of `--replace` indicates truthness
-## while its absence falseness).
-
-subset File of Str where *.IO.d; # convert to IO object to check the file exists
-
-multi MAIN('add', $key, $value, Bool :$replace) { ... }
-multi MAIN('remove', $key) { ... }
-multi MAIN('import', File, Str :$as) { ... } # omitting parameter name
-
-## This produces:
-## $ perl6 cli.pl
-## Usage:
-## cli.p6 [--replace] add <key> <value>
-## cli.p6 remove <key>
-## cli.p6 [--as=<Str>] 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 `$`/is named).
-```
-
-## APPENDIX A:
-### List of things
-
-```perl6
-## It's assumed by now you know the Perl6 basics. This section is just here to
-## list some common operations, but which are not in the "main part" of the
-## tutorial to avoid bloating it up.
-
-## Operators
-
-## Sort comparison - they return one value of the `Order` enum: `Less`, `Same`
-## and `More` (which numerify to -1, 0 or +1 respectively).
-1 <=> 4; # sort comparison for numerics
-'a' leg 'b'; # sort comparison for string
-$obj eqv $obj2; # sort comparison using eqv semantics
-
-## Generic ordering
-3 before 4; # True
-'b' after 'a'; # True
-
-## Short-circuit default operator - similar to `or` and `||`, but instead
-## returns the first *defined* value:
-say Any // Nil // 0 // 5; #=> 0
-
-## Short-circuit exclusive or (XOR) - returns `True` if one (and only one) of
-## its arguments is true
-say True ^^ False; #=> True
-
-## Flip flops - these operators (`ff` and `fff`, equivalent to P5's `..`
-## and `...`) are operators that take two predicates to test: They are `False`
-## until their left side returns `True`, then are `True` until their right
-## side returns `True`. Similar to ranges, you can exclude the iteration when
-## it become `True`/`False` by using `^` on either side. Let's start with an
-## example :
-for <well met young hero we shall meet later> {
- # by default, `ff`/`fff` smart-match (`~~`) against `$_`:
- if 'met' ^ff 'meet' { # Won't enter the if for "met"
- .say # (explained in details below).
- }
-
- if rand == 0 ff rand == 1 { # compare variables other than `$_`
- say "This ... probably will never run ...";
- }
-}
-
-## This will print "young hero we shall meet" (excluding "met"): the flip-flop
-## will start returning `True` when it first encounters "met" (but will still
-## return `False` for "met" itself, due to the leading `^` on `ff`), until it
-## sees "meet", which is when it'll start returning `False`.
-
-## The difference between `ff` (awk-style) and `fff` (sed-style) is that `ff`
-## will test its right side right when its left side changes to `True`, and can
-## get back to `False` right away (*except* it'll be `True` for the iteration
-## that matched) while `fff` will wait for the next iteration to try its right
-## side, once its left side changed:
-.say if 'B' ff 'B' for <A B C B A>; #=> B B
- # because the right-hand-side was tested
- # directly (and returned `True`).
- # "B"s are printed since it matched that
- # time (it just went back to `False`
- # right away).
-.say if 'B' fff 'B' for <A B C B A>; #=> B C B
- # The right-hand-side wasn't tested until
- # `$_` 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 it print again"
-}
-
-## You might also use a Whatever Star, which is equivalent to `True` for the
-## left side or `False` for the right:
-for (1, 3, 60, 3, 40, 60) { # Note: the parenthesis are superfluous here
- # (sometimes called "superstitious parentheses")
- .say if $_ > 50 ff *; # Once the flip-flop reaches a number greater
- # than 50, it'll never go back to `False`
- #=> 60 3 40 60
-}
-
-## You can also use this property to create an `if` that'll not go through the
-## first time:
-for <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
-}
-
-## The `===` operator is the value identity operator and uses `.WHICH` on the
-## objects to compare them while `=:=` is the container identity operator
-## and uses `VAR()` on the objects to compare them.
-```
-
-If you want to go further, you can:
-
- - Read the [Perl 6 Docs](https://docs.perl6.org/). This is a great
- resource on Perl6. If you are looking for something, use the search bar.
- This will give you a dropdown menu of all the pages referencing your search
- term (Much better than using Google to find Perl 6 documents!).
- - Read the [Perl 6 Advent Calendar](http://perl6advent.wordpress.com/). This
- is a great source of Perl 6 snippets and explanations. If the docs don't
- describe something well enough, you may find more detailed information here.
- This information may be a bit older but there are many great examples and
- explanations. Posts stopped at the end of 2015 when the language was declared
- stable and Perl 6.c was released.
- - Come along on `#perl6` at `irc.freenode.net`. The folks here are
- always helpful.
- - Check the [source of Perl 6's functions and
- classes](https://github.com/rakudo/rakudo/tree/nom/src/core). Rakudo is
- mainly written in Perl 6 (with a lot of NQP, "Not Quite Perl", a Perl 6 subset
- easier to implement and optimize).
- - Read [the language design documents](http://design.perl6.org). They explain
- P6 from an implementor point-of-view, but it's still very interesting.