class Mu
src
class Mu { ... }
The root of the Perl 6 type hierarchy. For the origin of the name, see
L<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 I<most undefined>
value.
Note that most classes do not derive from
Mu directly, but rather from
L<Any>.
Methods
defined
multi sub defined(Mu) returns Bool:D
multi method defined() returns Bool:D
Returns False on the type object, and True otherwise.
Bool
multi sub Bool(Mu) returns Bool:D
multi method Bool() returns Bool:D
Returns False on the type object, and True otherwise.
Str
multi method Str() returns Str
Returns a string representation of the invocant, intended to be machine
readable.
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.
perl
multi sub perl(Mu) returns Str
multi method perl() returns Str
Returns a Perlish representation of the object (i.e., can usually
be reparsed to regenerate the object).
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.
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.
bless
method bless(Mu $candidate, *%attrinit) returns Mu:D
Lower-level object construction method than new .
If you pass a Whatever as a candidate, it creates a new object
of the same type as the invocant, and then uses the named arguments
to initialize attributes.
If you pass something other than a Whatever object as a candidate,
it simply does the attribute initialization on the $candidate .
In both cases, the object with the attributes initialized is returned.
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).
CREATE
method CREATE() returns Mu:D
Allocates a new object of the same type as the invocant, without
initializating any attributes.
print
multi method print() returns Bool:D
Prints value to $*OUT after stringification using .Str method without
newline at end.
say
multi method say() returns Bool:D
Prints value to $*OUT after stringification using .gist method with
newline at end.
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 { ... } .
WHICH
multi method WHICH() returns ObjAt:D
Returns an object of type L<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 .
