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Diffstat (limited to 'perl6.html.markdown')
| -rw-r--r-- | perl6.html.markdown | 527 |
1 files changed, 350 insertions, 177 deletions
diff --git a/perl6.html.markdown b/perl6.html.markdown index b5a25a41..34ad70b7 100644 --- a/perl6.html.markdown +++ b/perl6.html.markdown @@ -1,9 +1,10 @@ --- category: language language: perl6 -filename: learnperl6.pl +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 @@ -37,11 +38,11 @@ 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 : +# Variable names can contain but not end with simple quotes and dashes, +# and can contain (and end with) underscores : # my $weird'variable-name_ = 5; # works ! -my $bool = True; # `True` and `False` are Perl 6's boolean +my $bool = True; # `True` and `False` are Perl 6's boolean values. my $inverse = !$bool; # You can invert a bool with the prefix `!` operator my $forced-bool = so $str; # And you can use the prefix `so` operator # which turns its operand into a Bool @@ -56,28 +57,32 @@ my @array = 1, 2, 3; say @array[2]; # Array indices start at 0 -- This is the third element -say "Interpolate an array using [] : @array[]"; -#=> Interpolate an array using [] : 1 2 3 +say "Interpolate all elements of an array using [] : @array[]"; +#=> Interpolate all elements of an array using [] : 1 2 3 @array[0] = -1; # Assign a new value to an array index @array[0, 1] = 5, 6; # Assign multiple values my @keys = 0, 2; -@array[@keys] = @letters; # Assign using an array +@array[@keys] = @letters; # Assignment using an array containing index values say @array; #=> a 6 b ## * 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. +# Hashes are pairs of keys and values. +# You can construct a Pair object using the syntax `Key => Value`. +# Hash tables are very fast for lookup, and are stored unordered. +# Keep in mind that keys get "flattened" in hash context, and any duplicated +# keys are deduplicated. my %hash = 1 => 2, 3 => 4; my %hash = foo => "bar", # keys get auto-quoted "some other" => "value", # trailing commas are okay ; -my %hash = <key1 value1 key2 value2>; # you can also create a hash - # from an even-numbered array -my %hash = key1 => 'value1', key2 => 'value2'; # same as this +# Even though hashes are internally stored differently than arrays, +# Perl 6 allows you to easily create a hash from an even numbered array: +my %hash = <key1 value1 key2 value2>; + +my %hash = key1 => 'value1', key2 => 'value2'; # same result as above # You can also use the "colon pair" syntax: # (especially handy for named parameters that you'll see later) @@ -92,7 +97,8 @@ say %hash{'key1'}; # You can use {} to get the value from a key say %hash<key2>; # If it's a string, you can actually use <> # (`{key1}` doesn't work, as Perl6 doesn't have barewords) -## * Subs (subroutines, or functions in most other languages). +## * Subs: subroutines or functions as most other languages call them are +# created with the `sub` keyword. sub say-hello { say "Hello, world" } sub say-hello-to(Str $name) { # You can provide the type of an argument @@ -193,6 +199,15 @@ sub mutate($n is rw) { say "\$n is now $n !"; } +my $m = 42; +mutate $m; # $n is now 43 ! + +# This works because we are passing the container $m to mutate. If we try +# to just pass a number instead of passing a variable it won't work because +# there is no container being passed and integers are immutable by themselves: + +mutate 42; # Parameter '$n' expected a writable container, but got Int value + # If what you want a copy instead, use `is copy`. # A sub itself returns a container, which means it can be marked as rw: @@ -228,10 +243,15 @@ unless False { say "Quite truthy" if True; # - Ternary conditional, "?? !!" (like `x ? y : z` in some other languages) -my $a = $condition ?? $value-if-true !! $value-if-false; +# returns $value-if-true if the condition is true and $value-if-false +# if it is false. +# my $result = $value condition ?? $value-if-true !! $value-if-false; -# - `given`-`when` looks like other languages' `switch`, but much more -# powerful thanks to smart matching and thanks to Perl 6's "topic variable", $_. +my $age = 30; +say $age > 18 ?? "You are an adult" !! "You are under 18"; + +# - `given`-`when` looks like other languages' `switch`, but is much more +# powerful thanks to smart matching and Perl 6's "topic variable", $_. # # This variable contains the default argument of a block, # a loop's current iteration (unless explicitly named), etc. @@ -242,6 +262,7 @@ my $a = $condition ?? $value-if-true !! $value-if-false; # Since other Perl 6 constructs use this variable (as said before, like `for`, # blocks, etc), this means the powerful `when` is not only applicable along with # a `given`, but instead anywhere a `$_` exists. + given "foo bar" { say $_; #=> foo bar when /foo/ { # Don't worry about smart matching yet – just know `when` uses it. @@ -336,16 +357,37 @@ if long-computation() -> $result { # - `eqv` is canonical equivalence (or "deep equality") (1, 2) eqv (1, 3); -# - `~~` is smart matching +# - 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 "has type" (can check superclasses and roles) + +1 ~~ Int; # True + +# Smart-matching against a boolean always returns that boolean (and will warn). + +1 ~~ True; # True +False ~~ True; # True + +# # General syntax is $arg ~~ &bool-returning-function; # For a complete list of combinations, use this table: # http://perlcabal.org/syn/S03.html#Smart_matching -'a' ~~ /a/; # true if matches regexp -'key' ~~ %hash; # true if key exists in hash -$arg ~~ &bool-returning-function; # `True` if the function, passed `$arg` - # as an argument, returns `True`. -1 ~~ Int; # "has type" (check superclasses and roles) -1 ~~ True; # smart-matching against a boolean always returns that boolean - # (and will warn). # You also, of course, have `<`, `<=`, `>`, `>=`. # Their string equivalent are also avaiable : `lt`, `le`, `gt`, `ge`. @@ -386,18 +428,22 @@ my @seq = 3, 9 ... * > 95; # 3 9 15 21 27 [...] 81 87 93 99; say @numbers; #=> 0 1 2 3 4 3 9 15 21 [...] 81 87 # (only 20 values) -## * And, Or +## * And &&, Or || 3 && 4; # 4, which is Truthy. Calls `.Bool` on `4` and gets `True`. 0 || False; # False. Calls `.Bool` on `0` ## * Short-circuit (and tight) versions of the above -$a && $b && $c; # Returns the first argument that evaluates to False, - # or the last argument. -$a || $b; +# Returns 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 +$a *= 2; # multiply and assignment. Equivalent to $a = $a * 2; $b %%= 5; # divisible by and assignment @array .= sort; # calls the `sort` method and assigns the result back @@ -408,19 +454,19 @@ $b %%= 5; # divisible by and assignment ## Unpacking ! # It's the ability to "extract" arrays and keys (AKA "destructuring"). # It'll work in `my`s and in parameter lists. -my ($a, $b) = 1, 2; -say $a; #=> 1 -my ($, $, $c) = 1, 2, 3; # keep the non-interesting anonymous -say $c; #=> 3 +my ($f, $g) = 1, 2; +say $f; #=> 1 +my ($, $, $h) = 1, 2, 3; # keep the non-interesting anonymous +say $h; #=> 3 my ($head, *@tail) = 1, 2, 3; # Yes, it's the same as with "slurpy subs" my (*@small) = 1; -sub foo(@array [$fst, $snd]) { +sub unpack_array(@array [$fst, $snd]) { say "My first is $fst, my second is $snd ! All in all, I'm @array[]."; # (^ remember the `[]` to interpolate the array) } -foo(@tail); #=> My first is 2, my second is 3 ! All in all, I'm 2 3 +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, @@ -579,66 +625,95 @@ multi with-or-without-you { ### Scoping -# In Perl 6, contrarily to many scripting languages (like Python, Ruby, PHP), -# you are to declare your variables before using them. You know `my`. -# (there are other declarators, `our`, `state`, ..., which we'll see later). +# 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 $foo = 'Foo'; -sub foo { - my $bar = 'Bar'; - sub bar { - say "$foo $bar"; +my $file_scoped = 'Foo'; +sub outer { + my $outer_scoped = 'Bar'; + sub inner { + say "$file_scoped $outer_scoped"; } - &bar; # return the function + &inner; # return the function } -foo()(); #=> 'Foo Bar' +outer()(); #=> 'Foo Bar' -# As you can see, `$foo` and `$bar` were captured. +# As you can see, `$file_scoped` and `$outer_scoped` were captured. # But if we were to try and use `$bar` outside of `foo`, # the variable would be undefined (and you'd get a compile time error). -# Perl 6 has another kind of scope : dynamic scope. -# They use the twigil (composed sigil) `*` to mark dynamically-scoped variables: -my $*a = 1; -# Dyamically-scoped variables depend on the current call stack, -# instead of the current block depth. -sub foo { - my $*foo = 1; - bar(); # call `bar` in-place +### Twigils + +# There are many special `twigils` (composed sigil's) in Perl 6. +# Twigils define the variables' scope. +# The * and ? twigils work on standard variables: +# * Dynamic variable +# ? Compile-time variable +# The ! and the . twigils are used with Perl 6's objects: +# ! Attribute (class member) +# . Method (not really a variable) + +# `*` Twigil: Dynamic Scope +# These variables use the`*` twigil to mark dynamically-scoped variables. +# Dynamically-scoped variables are looked up through the caller, not through +# the outer scope + +my $*dyn_scoped_1 = 1; +my $*dyn_scoped_2 = 10; + +sub say_dyn { + say "$*dyn_scoped_1 $*dyn_scoped_2"; } -sub bar { - say $*foo; # `$*foo` will be looked in the call stack, and find `foo`'s, - # even though the blocks aren't nested (they're call-nested). - #=> 1 + +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 he 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 $*dyn_scoped_2 in call_say_dyn + # so now its value has changed. ### Object Model -# You declare a class with the keyword `class`, fields with `has`, -# methods with `method`. Every attribute that is private is named `$!attr`. -# Immutable public attributes are named `$.attr` +# To call a method on an object, add a dot followed by the method name: +# => $object.method +# Classes are declared with the `class` keyword. Attributes are declared +# with the `has` keyword, and methods declared with `method`. +# Every attribute that is private uses the ! twigil for example: `$!attr`. +# Immutable public attributes use the `.` twigil. # (you can make them mutable with `is rw`) +# The easiest way to remember the `$.` twigil is comparing it to how methods +# are called. # Perl 6's object model ("SixModel") is very flexible, # and allows you to dynamically add methods, change semantics, etc ... -# (this will not be covered here, and you should refer to the Synopsis). +# (these will not all be covered here, and you should refer to: +# https://docs.perl6.org/language/objects.html. -class A { - has $.field; # `$.field` is immutable. - # From inside the class, use `$!field` to modify it. - has $.other-field is rw; # You can mark a public attribute `rw`. - has Int $!private-field = 10; +class Attrib-Class { + has $.attrib; # `$.attrib` is immutable. + # From inside the class, use `$!attrib` to modify it. + has $.other-attrib is rw; # You can mark a public attribute `rw`. + has Int $!private-attrib = 10; method get-value { - $.field + $!private-field; + $.attrib + $!private-attrib; } - method set-value($n) { - # $.field = $n; # As stated before, you can't use the `$.` immutable version. - $!field = $n; # This works, because `$!` is always mutable. + method set-value($param) { # Methods can take parameters + $!attrib = $param; # This works, because `$!` is always mutable. + # $.attrib = $param; # Wrong: You can't use the `$.` immutable version. - $.other-field = 5; # This works, because `$.other-field` is `rw`. + $.other-attrib = 5; # This works, because `$.other-attrib` is `rw`. } method !private-method { @@ -646,33 +721,44 @@ class A { } }; -# Create a new instance of A with $.field set to 5 : -# Note: you can't set private-field from here (more later on). -my $a = A.new(field => 5); -$a.get-value; #=> 15 -#$a.field = 5; # This fails, because the `has $.field` is immutable -$a.other-field = 10; # This, however, works, because the public field - # is mutable (`rw`). - -## Perl 6 also has inheritance (along with multiple inheritance) - -class A { - has $.val; - - submethod not-inherited { - say "This method won't be available on B."; - say "This is most useful for BUILD, which we'll see later"; +# Create a new instance of Attrib-Class with $.attrib set to 5 : +# Note: you can't set private-attribute from here (more later on). +my $class-obj = Attrib-Class.new(attrib => 5); +say $class-obj.get-value; #=> 15 +#$class-obj.attrib = 5; # This fails, because the `has $.attrib` is immutable +$class-obj.other-attrib = 10; # This, however, works, because the public + # attribute is mutable (`rw`). + +## Object Inheritance +# Perl 6 also has inheritance (along with multiple inheritance) +# While `method`'s are inherited, `submethod`'s are not. +# Submethods are useful for object construction and destruction tasks, +# such as BUILD, or methods that must be overriden by subtypes. +# We will learn about BUILD later on. + +class Parent { + has $.age; + has $.name; + # This submethod won't be inherited by Child. + submethod favorite-color { + say "My favorite color is Blue"; } - - method bar { $.val * 5 } + # This method is inherited + method talk { say "Hi, my name is $!name" } } -class B is A { # inheritance uses `is` - method foo { - say $.val; - } - - method bar { $.val * 10 } # this shadows A's `bar` +# 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, he knows how to say his name. + +my Child $Madison .= new(age => 1, name => 'Madison'); +$Madison.talk; # prints "Goo goo ga ga" due to the overrided 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. @@ -680,11 +766,7 @@ class B is A { # inheritance uses `is` # `$a .= b` is the same as `$a = $a.b`) # Also note that `BUILD` (the method called inside `new`) # will set parent properties too, so you can pass `val => 5`. -my B $b .= new(val => 5); -# $b.not-inherited; # This won't work, for reasons explained above -$b.foo; # prints 5 -$b.bar; #=> 50, since it calls B's `bar` ## Roles are supported too (also called Mixins in other languages) role PrintableVal { @@ -699,8 +781,8 @@ class Item does PrintableVal { has $.val; # When `does`-ed, a `role` literally "mixes in" the class: - # the methods and fields are put together, which means a class can access - # the private fields/methods of its roles (but not the inverse !): + # 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++; } @@ -717,34 +799,76 @@ class Item does PrintableVal { ### Exceptions # Exceptions are built on top of classes, in the package `X` (like `X::IO`). -# Unlike many other languages, in Perl 6, you put the `CATCH` block *within* the -# block to `try`. By default, a `try` has a `CATCH` block that catches -# any exception (`CATCH { default {} }`). +# 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: +die X::AdHoc.new(payload => 'Error!'); + +# In Perl 6, `orelse` is similar to the `or` operator, except it only matches +# undefined variables instead of anything evaluating as false. +# Undefined values include: `Nil`, `Mu` and `Failure` as well as `Int`, `Str` +# and other types that have not been initialized to any value yet. +# You can check if something is defined or not using the defined method: +my $uninitialized; +say $uninitiazilzed.defined; #> False +# When using `orelse` it will disarm the exception and alias $_ to that failure +# This will avoid it being automatically handled and printing lots of scary +# error messages to the screen. +# We can use the exception method on $_ to access the exception +open 'foo' orelse say "Something happened {.exception}"; +# This also works: +open 'foo' orelse say "Something happened $_"; #> Something happened + #> Failed to open file foo: no such file or directory +# Both of those above work but in case we get an object from the left side that +# is not a failure we will probably get a warning. We see below how we can use +# `try` and `CATCH` to be more specific with the exceptions we catch. + +## Using `try` and `CATCH` +# By using `try` and `CATCH` you can contain and handle exceptions without +# disrupting the rest of the program. `try` will set the last exception to +# the special variable `$!` Note: This has no relation to $!variables. +try open 'foo'; +say "Well, I tried! $!" if defined $!; #> Well, I tried! Failed to open file + #foo: no such file or directory +# Now, what if we want more control over handling the exception? +# Unlike many other languages, in Perl 6, you put the `CATCH` block *within* +# the block to `try`. Similar to how $_ was set when we 'disarmed' the +# exception with orelse, we also use $_ in the CATCH block. +# Note: ($! is only set *after* the `try` block) +# By default, a `try` has a `CATCH` block that catches +# any exception (`CATCH { default {} }`). + +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 handle the exceptions you want: try { open 'foo'; - CATCH { - when X::AdHoc { say "unable to open file !" } + CATCH { # In the `CATCH` block, the exception is set to $_ + when X::AdHoc { say "Error: $_" } + #=>Error: Failed to open file /dir/foo: no such file or directory + # Any other exception will be re-raised, since we don't have a `default` - # Basically, if a `when` matches (or there's a `default`) marks the exception as - # "handled" so that it doesn't get re-thrown from the `CATCH`. + # Basically, if a `when` matches (or there's a `default`) marks the + # exception as + # "handled" so that it doesn't get re-thrown from the `CATCH`. # You still can re-throw the exception (see below) by hand. } } -# You can throw an exception using `die`: -die X::AdHoc.new(payload => 'Error !'); - -# You can access the last exception with `$!` (use `$_` in a `CATCH` block) - -# There are also some subtelties to exceptions. Some Perl 6 subs return a `Failure`, -# which is a kind of "unthrown exception". They're not thrown until you tried to look -# at their content, unless you call `.Bool`/`.defined` on them - then they're handled. -# (the `.handled` method is `rw`, so you can mark it as `False` back yourself) +# There are also some subtleties to exceptions. Some Perl 6 subs return a +# `Failure`, which is a kind of "unthrown exception". They're not thrown until +# you tried to look at their content, unless you call `.Bool`/`.defined` on +# them - then they're handled. +# (the `.handled` method is `rw`, so you can mark it as `False` back yourself) # -# You can throw a `Failure` using `fail`. Note that if the pragma `use fatal` is on, -# `fail` will throw an exception (like `die`). +# 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"; @@ -764,21 +888,25 @@ try { # 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're not supposed to use the package keyword, usually: -# you use `class Package::Name::Here;` to declare a class, -# or if you only want to export variables/subs, you can use `module`: + +# You can use a module (bring its declarations into scope) with `use` +use JSON::Tiny; # if you installed Rakudo* or Panda, you'll have this module +say from-json('[1]').perl; #=> [1] + +# Declare your own packages like this: +# `class Package::Name::Here;` to declare a class, or if you only want to +# export variables/subs, you can use `module`. If you're coming from Perl 5 +# please note you're not usually supposed to use the `package` keyword. + 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 -grammar Parse::Text::Grammar { # A grammar is a package, which you could `use` -} -# You can use a module (bring its declarations into scope) with `use` -use JSON::Tiny; # if you installed Rakudo* or Panda, you'll have this module -say from-json('[1]').perl; #=> [1] +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: @@ -790,25 +918,33 @@ my $actions = JSON::Tiny::Actions.new; # 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` (happens at `INIT` time -- see "Phasers" below) +## * `our` declarations happen at `INIT` time -- (see "Phasers" below) # It's like `my`, but it also creates a package variable. # (All packagish things (`class`, `role`, etc) are `our` by default) -module Foo::Bar { - our $n = 1; # note: you can't put a type constraint on an `our` variable - our sub inc { +module Var::Increment { + our $our-var = 1; # Note: you can't put a type constraint like Int on an + my $my-var = 22; # `our` variable. + our sub Inc { + our sub available { # If you try to make inner `sub`s `our`... # Better know what you're doing (Don't !). - say "Don't do that. Seriously. You'd get burned."; + say "Don't do that. Seriously. You'll get burned."; } + my sub unavailable { # `my sub` is the default - say "Can't access me from outside, I'm my !"; + say "Can't access me from outside, I'm 'my'!"; } - say ++$n; # increment the package variable and output its value + say ++$our-var; # Increment the package variable and output its value } + } -say $Foo::Bar::n; #=> 1 -Foo::Bar::inc; #=> 2 -Foo::Bar::inc; #=> 3 +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` (happens at `BEGIN` time) # You can use the `constant` keyword to declare a compile-time variable/symbol: @@ -845,10 +981,11 @@ for ^5 -> $a { ### Phasers # Phasers in Perl 6 are blocks that happen at determined points of time in your -# program. When the program is compiled, when a for loop runs, when you leave a -# block, when an exception gets thrown ... (`CATCH` is actually a phaser !) +# program. They are called phasers because they mark a change in the phase +# of a program. For example, when the program is compiled, a for loop runs, +# you leave a block, or an exception gets thrown. (`CATCH` is actually a phaser !) # Some of them can be used for their return values, some of them can't -# (those that can have a "[*]" in the beginning of their explanation text). +# (those that can have a "[*]" in the beginning of their explanation text). # Let's have a look ! ## * Compile-time phasers @@ -947,15 +1084,25 @@ constant thrice = gather for ^3 { say take $_ }; # Doesn't print anything # versus: constant thrice = eager gather for ^3 { say take $_ }; #=> 0 1 2 -# - `lazy` - Defer actual evaluation until value is fetched (forces lazy context) -# Not yet implemented !! +### Iterables +# Iterables are objects that can be iterated similar to the `for` construct +# `flat`, flattens iterables: +say (1, 10, (20, 10) ); #> (1 10 (20 10)) Notice how grouping is maintained +say (1, 10, (20, 10) ).flat; #> (1 10 20 10) Now the iterable is flat +# - `lazy` - Defer actual evaluation until value is fetched (forces lazy context) +my @lazy-array = (1..100).lazy; +say @lazy-array.is-lazy; #> True # Check for lazyness with the `is-lazy` method. +say @lazy-array; #> [...] List has not been iterated on! +my @lazy-array { .print }; # This works and will only do as much work as is +# needed. +[//]: # ( TODO explain that gather/take and map are all lazy) # - `sink` - An `eager` that discards the results (forces sink context) constant nilthingie = sink for ^3 { .say } #=> 0 1 2 say nilthingie.perl; #=> Nil -# - `quietly` - Supresses warnings -# Not yet implemented ! +# - `quietly` blocks will suppress warnings: +quietly { warn 'This is a warning!' }; #=> No output # - `contend` - Attempts side effects under STM # Not yet implemented ! @@ -965,7 +1112,7 @@ say nilthingie.perl; #=> Nil ## Everybody loves operators ! Let's get more of them # The precedence list can be found here: -# http://perlcabal.org/syn/S03.html#Operator_precedence +# https://docs.perl6.org/language/operators#Operator_Precedence # But first, we need a little explanation about associativity: # * Binary operators: @@ -1088,10 +1235,11 @@ sub add($a, $b) { $a + $b } say [[&add]] 1, 2, 3; #=> 6 ## * Zip meta-operator -# This one is an infix meta-operator than also can be used as a "normal" operator. -# It takes an optional binary function (by default, it just creates a pair), -# and will pop one value off of each array and call its binary function on these -# until it runs out of elements. It returns an array with all of these new elements. +# This one is an infix meta-operator than also can be used as a "normal" +# operator. It takes an optional binary function (by default, it just creates +# a pair), and will pop one value off of each array and call its binary function +# on these until it runs out of elements. It returns an array with all of these +# new elements. (1, 2) Z (3, 4); # ((1, 3), (2, 4)), since by default, the function makes an array 1..3 Z+ 4..6; # (5, 7, 9), using the custom infix:<+> function @@ -1158,14 +1306,15 @@ say @fib[^10]; #=> 1 1 2 3 5 8 13 21 34 55 # (grammars are actually classes) # - Earliest declaration wins say so 'a' ~~ /a/; #=> True -say so 'a' ~~ / a /; # More readable with some spaces! +say so 'a' ~~ / a /; #=> True # More readable with some spaces! # In all our examples, we're going to use the smart-matching operator against # a regexp. We're converting the result using `so`, but in fact, it's # returning a `Match` object. They know how to respond to list indexing, # hash indexing, and return the matched string. # The results of the match are available as `$/` (implicitly lexically-scoped). -# You can also use the capture variables (`$0`, `$1`, ... starting at 0, not 1 !). +# You can also use the capture variables which start at 0: +# `$0`, `$1', `$2`... # # You can also note that `~~` does not perform start/end checking # (meaning the regexp can be matched with just one char of the string), @@ -1173,50 +1322,63 @@ say so 'a' ~~ / a /; # More readable with some spaces! # In Perl 6, you can have any alphanumeric as a literal, # everything else has to be escaped, using a backslash or quotes. -say so 'a|b' ~~ / a '|' b /; # `True`. Wouln't mean the same if `|` wasn't escaped +say so 'a|b' ~~ / a '|' b /; # `True`. Wouldn't mean the same if `|` wasn't escaped say so 'a|b' ~~ / a \| b /; # `True`. Another way to escape it. # The whitespace in a regexp is actually not significant, -# unless you use the `:s` (`:sigspace`, significant space) modifier. -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. - +# unless you use the `:s` (`:sigspace`, significant space) adverb. +say so 'a b c' ~~ / a b c /; #> `False`. Space is not significant here +say so 'a b c' ~~ /:s a b c /; #> `True`. We added the modifier `:s` here. +# If we use only one space between strings in a regex, Perl 6 will warn us: +say so 'a b c' ~~ / a b c /; #> 'False' #> Space is not significant here; please +# use quotes or :s (:sigspace) modifier (or, to suppress this warning, omit the +# space, or otherwise change the spacing) +# To fix this and make the spaces less ambiguous, either use at least two +# spaces between strings or use the `:s` adverb. + +# As we saw before, we can embed the `:s` inside the slash delimiters, but we can +# also put it outside of them if we specify `m` for 'match': +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` +# Use the :i adverb to specify case insensitivity: +say so 'ABC' ~~ m:i{a b c}; #> `True` # It is, however, important as for how modifiers (that you're gonna see just below) # are applied ... ## Quantifying - `?`, `+`, `*` and `**`. # - `?` - 0 or 1 -so 'ac' ~~ / a b c /; # `False` -so 'ac' ~~ / a b? c /; # `True`, the "b" matched 0 times. -so 'abc' ~~ / a b? c /; # `True`, the "b" matched 1 time. +so 'ac' ~~ / a b c /; # `False` +so 'ac' ~~ / a b? c /; # `True`, the "b" matched 0 times. +so 'abc' ~~ / a b? c /; # `True`, the "b" matched 1 time. # ... As you read just before, whitespace is important because it determines # which part of the regexp is the target of the modifier: -so 'def' ~~ / a b c? /; # `False`. Only the `c` is optional -so 'def' ~~ / ab?c /; # `False`. Whitespace is not significant +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` # - `+` - 1 or more -so 'ac' ~~ / a b+ c /; # `False`; `+` wants at least one matching -so 'abc' ~~ / a b+ c /; # `True`; one is enough -so 'abbbbc' ~~ / a b+ c /; # `True`, matched 4 "b"s +so 'ac' ~~ / a b+ c /; # `False`; `+` wants at least one matching +so 'abc' ~~ / a b+ c /; # `True`; one is enough +so 'abbbbc' ~~ / a b+ c /; # `True`, matched 4 "b"s # - `*` - 0 or more -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. +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) +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 @@ -1460,7 +1622,18 @@ for <a b c> { 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. + - 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 explainations. 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 + explainations. 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. + + [//]: # ( vim: set filetype=perl softtabstop=2 shiftwidth=2 expandtab cc=80 : ) |