class Mu

The root of the Perl 6 type hierarchy.

class Mu { ... }

The root of the Perl 6 type hierarchy. For the origin of the name, see http://en.wikipedia.org/wiki/Mu_%28negative%29. One can also say that there are many undefined values in Perl 6, and Mu is the most undefined value.

Note that most classes do not derive from Mu directly, but rather from Any.

Methods

routine defined

multi sub    defined(Mu) returns Bool:D
multi method defined()   returns Bool:D

Returns False on the type object, and True otherwise.

routine Bool

multi sub    Bool(Mu) returns Bool:D
multi method Bool()   returns Bool:D

Returns False on the type object, and True otherwise.

method Str

multi method Str()   returns Str

Returns a string representation of the invocant, intended to be machine readable.

routine gist

multi sub    gist(Mu) returns Str
multi method gist()   returns Str

Returns a string representation of the invocant, optimized for fast recognition by humans.

The default gist method in Mu re-dispatches to the perl method, but many built-in classes override it to something more specific.

routine perl

multi sub    perl(Mu) returns Str
multi method perl()   returns Str

Returns a Perlish representation of the object (i.e., can usually be re-parsed to regenerate the object).

method clone

method clone(*%twiddles)

Creates a shallow clone of the invocant. If named arguments are passed to it, their values are used in every place where an attribute name matches the name of a named argument.

method new

multi method new(*%attrinit)

Default method for constructing (create + initialize) new objects of a class. This method expects only named arguments which are then used to initialize attributes with accessors of the same name.

Classes may provide their own new method to override this default.

method bless

method bless(*%attrinit) returns Mu:D

Lower-level object construction method than new.

Creates a new object of the same type as the invocant, uses the named arguments to initialize attributes, and returns the created object.

You can use this method when writing custom constructors:

class Point {
    has $.x;
    has $.y;
    multi method new($x, $y) {
        self.bless(:$x, :$y);
    }
}
my $p = Point.new(-1, 1);

(Though each time you write a custom constructor, remember that it makes subclassing harder).

method CREATE

method CREATE() returns Mu:D

Allocates a new object of the same type as the invocant, without initializing any attributes.

method print

multi method print() returns Bool:D

Prints value to $*OUT after stringification using .Str method without newline at end.

method say

multi method say() returns Bool:D

Prints value to $*OUT after stringification using .gist method with newline at end.

method ACCEPTS

multi method ACCEPTS(Mu:U: $other)

Performs a type check. Returns True if $other conforms to the invocant (which is always a type object or failure).

This is the method that is triggered on smart-matching against type objects, for example in if $var ~~ Int { ... }.

method WHICH

multi method WHICH() returns ObjAt:D

Returns an object of type ObjAt which uniquely identifies the object. Value types override this method which makes sure that two equivalent objects return the same return value from WHICH.

method WHERE

method WHERE() returns Int

Returns an Int representing the memory address of the object.

method WHY

multi method WHY()

Returns the attached Pod value. For instance,

    sub cast(Spell $s)
    #= Initiate a specified spell normally
    #= (do not use for class 7 spells)
    {
	do-raw-magic($s);
    }
    say &cast.WHY;

prints

Initiate a specified spell normally (do not use for class 7 spells)

See the documentation specification for details about attaching Pod to variables, classes, functions, methods, etc.

trait is export

multi sub trait_mod:<is>(Mu:U \type, :$export!)

Marks a type as being exported, that is, available to external users.

my class SomeClass is export { }

A user of a module or class automatically gets all the symbols imported that are marked as is export.

Type graph

Below you should see a clickable image showing the type relations for Mu that links to the documentation pages for the related types. If not, try the PNG version instead.

perl6-type-graph Mu Mu Any Any Any->Mu Junction Junction Junction->Mu

This documentation was generated from Mu.pod.