This file was automatically generated from http://svn.pugscode.org/pugs/docs/Perl6/API/Scalar.pod on Mon Sep 10 11:50:25 2007 GMT, revision 17733.
Scalar API reference
use Scalar
The following functions are exported by default:
our Bool multi Scalar::defined ( Any $thing ) our Bool multi Scalar::defined ( Any $thing, ::role )
defined returns true if the parameter has a value and that value is
not the undefined value (per undef), otherwise false is returned.
Same as Perl 5, only takes extra optional argument to ask if value is defined with respect to a particular role:
$x.defined(SomeRole);
A value may be defined according to one role and undefined according to another. Without the extra argument, defaults to the definition of defined supplied by the type of the object.
our multi Any::undefine( Any $thing )
Takes any variable as a parameter and attempts to "remove" its definition. For simple scalar variables this means assigning the undefined value to the variable. For objects, this is equivalent to invoking their undefine method. For arrays, hashes and other complex data, this might require emptying the structures associated with the object.
In all cases, calling undefine on a variable
should place the object in the same state as if it was just
declared.
constant Scalar Scalar::undef
Returns the undefined scalar object. undef has no value at
all, but for historical compatibility, it will numify to 0
and stringify to the empty string, potentially generating a
warning in doing so. There are two ways to determine if a
value equal to undef: the defined function (or method) can
be called or the // (or orelse) operator can be used.
undef is also considered to be false in a boolean context.
Such a conversion does not generate a warning.
Perl 5's unary undef function is renamed undefine to avoid
confusion with the value undef (which is always 0-ary now).
These functions are also provided as methods, which can be called an any scalar type:
our Bool multi method Scalar::defined ( Scalar $thing: ) our Bool multi method Scalar::defined ( Scalar $thing: ::role )
Returns a true value if $thing is defined. See above for the meaning
of the ::role argument.
our multi method Any::undefine ( Any $thing: )
Sets the invocant ($thing) to an undefined value.