TITLE

String or object that can act as a string


SUBTITLE

Common role for string types (such as Str).


root

Invocable code object


role Callable


Object that can be treated as a date


role Dateish


Distribution


role Distribution


Support for character encodings.


role Encoding


Iterators that can predict number of values


role PredictiveIterator


Provide leading/trailing doc functionality


class RakuAST::Doc::DeclaratorTarget


Number stored as numerator and denominator


role Rational


Non-complex number


role Real


para

L<Examples| file:../examples/index.podlite>


L<Download |file:../download/index.podlite>


React

=begin React :component<HeaderCol> :id<menu> 
=para L<Documentation|/doc/introduction>
=para L<Modules| /mods>
=para L<Examples| file:../examples/index.podlite>
=para L<Download |file:../download/index.podlite>
=para L<About|file:../about/index.podlite>
=para 🔍 K<⌘K>/K<ctrl-K>
=end React


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FOOTER

role Stringy


A type for subroutines and operators. Subs are created with the C<sub>
declarator keyword followed by an optional
L<identifier|/language/syntax#Identifiers>. This
L<short tutorial explains how operators are declared|/language/optut>.
For details of a sub's parameter list, see L<C<Signature>|/type/Signature>.


Note that subs that go by the same name as
L<coercers|/language/typesystem#Coercion> will not take precedence over
them. Use the C<&>-sigil to call them.


sub Int(Str $s){'what?'};
say [Int, Int('42'),&Int('42')];
# OUTPUT: «[(Int) 42 what?]␤»


X<|Syntax,my (Sub)>X<|Syntax,our (Sub)>
Subs can be nested and scoped with C<my> and C<our>, whereby C<my> is the
default. A sub declared with C<my> cannot be reached from any outer scope. An
C<our> scoped sub will not redefine a sub of the same name in the outer scope.
Any sub can be accessed via a closure from any outer scope. For instance, in
this example


sub can-be-seener( $whatever ) {
  my sub can-be-seen ( $objection ) {
    return $whatever but $objection;
  }
  return &can-be-seen
}


my $objectioner = can-be-seener( "Really?");
say $objectioner(42).Int; # OUTPUT: «42␤»


C<$objectioner> will contain the C<can-be-seen> subroutine, even if it has been
declared in another scope; calling it with C<42> will return C<"Really?"> with
the number 42 mixed in, as shown in the last sentence.


head

Operators are also C<Sub>s. Their definition includes
L<the category they belong to|/language/operators#Operator_classification>
and their
L<code, precedence and associativity|/language/functions#Defining_operators>.
The syntax used in their definition is an example of
L<extended identifiers|/language/syntax#Extended_identifiers>.


Traits
X<|Syntax,trait_mod (declarator)>


A C<Trait> is a sub that is applied at compile time to various objects like
classes, routines or L<containers|/language/phasers#index-entry-will_trait>. It
is declared with the C<trait_mod> declarator followed by a colon and a string
literal containing the name of the trait. A single positional parameter defines
the type of the object that the trait is applied to. A single named argument
defines the secondary name and may carry arguments when the trait is called.
Traits are a special grammar category and are allowed to be placed after most
language object names or parameter lists.


say 'start';
multi trait_mod:<is>(Sub $s, :$foo){
    say "⟨is foo⟩ has been called with ⟨$foo⟩ on {$s.WHICH}";
}
sub bar() is foo<oi‽> {
    say 'bar has been called'
}
bar();
# OUTPUT: «⟨is foo⟩ has been called with ⟨oi‽⟩ on Sub|47563000␤start␤bar has been called␤»


Use L<destructuring|/language/signatures#Destructuring_arguments> to call traits
with complex arguments.


multi trait_mod:<is>(Variable $a, :@foo [$firstpos, *@restpos, :$named, *%restnameds]) {
    say [$firstpos, @restpos, $named, %restnameds]
}
my $x is foo[1,2,3,:named<a>, :2b, :3c] = 1
# OUTPUT: «[1 [2 3] a {b => 2, c => 3}]␤»


Despite its funky syntax, a trait is just a normal C<Sub>. We can apply traits
to it (or even themselves) and we can apply traits to objects at runtime.


multi trait_mod:<is> (Sub $s, :$foo) is foo {
    say 'is foo called'
}
sub bar {}
&trait_mod:<is>(&bar, :foo);
# OUTPUT: «is foo called␤is foo called␤»


Native integer


class int


Dual value number and string


class Allomorph


Thing/object


class Any


Abstract representation of a piece of source code


class AST


Integer (native storage at the platform's atomic operation size)


class atomicint


Code object with its own lexical scope


class Block


Captures the current frame state


class CallFrame


Code object


class Code


Encapsulates instructions about how strings should be sorted


class Collation


Information related to the compiler that is being used


class Compiler


Complex number


class Complex


Dual value complex number and string


class ComplexStr


Object that can be treated as both a string and number


class Cool


Scheduler that synchronously executes code on the current thread


class CurrentThreadScheduler


Calendar date


class Date


Calendar date with time


class DateTime


Distribution::Hash


class Distribution::Hash


Distribution::Locally


class Distribution::Locally


Distribution::Path


class Distribution::Path


Every one of the resources installed with a distribution


class Distribution::Resource


Length of time


class Duration


Management of available encodings


class Encoding::Registry


Rational number (arbitrary-precision)


class FatRat


Rakudo-specific class that wraps around code in other languages (generally NQP)


class ForeignCode


Convert values to a string given a format specification


class Format


Produce Callable for given format specification


class Formatter


An object for performing batches of work in parallel with ordered
output


class HyperSeq


Placeholder for multiple unspecified values/arguments


class HyperWhatever


Specific moment in time


class Instant


Integer (arbitrary-precision)


class Int


Dual value integer and string


class IntStr


Logical superposition of values


class Junction


Tagged location in the source code


class Label


A non-blocking, non-re-entrant, mutual exclusion lock


class Lock::Async


Compile-time routine


class Macro


Member function


class Method


The root of the Raku type hierarchy.


class Mu


Absence of a value or a benign failure


class Nil


Floating-point number


class Num


Number or object that can act as a number


role Numeric


Dual value floating-point number and string


class NumStr


Unique identification for an object


class ObjAt


Element of a Signature


class Parameter


Perl related information


class Perl


Item container with custom storage and retrieval


class Proxy


Performs batches of work in parallel without respecting original
order.


class RaceSeq


Raku related information


class Raku


Namespace for holding RakuAST related classes


package RakuAST


Contains the information of a RakuDoc block


class RakuAST::Doc::Block


Contains the declarator docs of a RakuAST object


class RakuAST::Doc::Declarator


Contains the information about RakuDoc markup


class RakuAST::Doc::Markup


Contains the information about a RakuDoc paragraph


class RakuAST::Doc::Paragraph


Rational number (limited-precision)


class Rat


Dual value rational number and string


class RatStr


Code object with its own lexical scope and return handling


class Routine


Holds all information needed to unwrap a wrapped routine.


class Routine::WrapHandle


A mostly transparent container used for indirections


class Scalar


Parameter list pattern


class Signature


String of characters


class Str


Contains the result of a string transformation.


class StrDistance


Member function that is not inherited by subclasses


class Submethod


Collect performance state for analysis


class Telemetry


Instrument for collecting Thread data


class Telemetry::Instrument::Thread


Instrument for collecting ThreadPoolScheduler data


class Telemetry::Instrument::ThreadPool


Instrument for collecting getrusage data


class Telemetry::Instrument::Usage


Performance data over a period


class Telemetry::Period


Telemetry instrument pod


class Telemetry::Sampler


Unsigned integer (arbitrary-precision)


Subset UInt


Unique identification for value types


class ValueObjAt


Object representation of a variable for use in traits


class Variable


Module version descriptor


class Version


Placeholder for the value of an unspecified argument


class Whatever


Code object constructed by Whatever-priming


class WhateverCode


Subroutine


class Sub


C<StrDistance> objects are used to represent the return of the
L<string transformation|/language/operators#tr///_in-place_transliteration> operator.


say (($ = "fold") ~~ tr/old/new/).^name;  # OUTPUT: «StrDistance␤»


A C<StrDistance> object will stringify to the resulting string after the
transformation, and will numify to the distance between the two strings.


code

=begin code
my $str = "fold";
my $str-dist = ($str ~~ tr/old/new/);
say ~$str-dist;  # OUTPUT: «fnew␤»
say +$str-dist;  # OUTPUT: «3␤»
=end code


This is actually a class attribute, and called as a method returns the string
before the transformation:


Also a class attribute, returns the string after the transformation:


Returns C<True> if C<before> is different from C<after>.


The Raku Knowledge Base


See Also