class ForeignCode does Callable {}

[1]

ForeignCode is a Raku wrapper around code that is not written originally in that language; its intention is to use these blocks of code in Callable contexts easily. For instance, subs have some anonymous functions that are actually ForeignCode.

sub does-nothing(){};
say $_.name ~ ' → ' ~ $_.^name for &does-nothing.^methods;
# OUTPUT: «<anon> → ForeignCode␤<anon> → ForeignCode␤soft → Method␤…» 

This script will map method names to their class, and it shows that routines, in particular, have several methods that are actually ForeignCode instead of Methods.

Methods §

method arity §

method arity()

Returns the arity of the enclosed code.

method count §

method count()

Returns the number of arguments the enclosed code needs.

method signature §

method signature( ForeignCode:D: )

Returns the signature of the enclosed code.

method name §

method name()

Returns the name of the enclosed code, or <anon> if it has not received any.

method gist §

method gist( ForeignCode:D: )

Returns the name of the code by calling name.

method Str §

method Str( ForeignCode:D: )

Returns the name of the code by calling name.

Type Graph §

Routines supplied by role Callable §

ForeignCode does role Callable, which provides the following routines:

(Callable) method CALL-ME §

method CALL-ME(Callable:D $self: |arguments)

This method is required for the ( ) postcircumfix operator and the .( ) postcircumfix operator. It's what makes an object actually call-able and needs to be overloaded to let a given object act like a routine. If the object needs to be stored in a &-sigiled container, it has to implement Callable.

class A does Callable {
    submethod CALL-ME(|c){ 'called' }
}
my &a = A;
say a(); # OUTPUT: «called␤»

Applying the Callable role is not a requirement to make an object callable; if a class simply wants to add subroutine-like semantics in a regular scalar container, the submethod CALL-ME can be used for that.

class A {
    has @.values;
    submethod CALL-ME(Int $x where 0 <= * < @!values.elems) {
        @!values[$x]
    }
}
my $a = A.new: values => [4,5,6,7];
say $a(2); # OUTPUT: «6␤»

(Callable) method Capture §

Defined as:

method Capture()

Throws X::Cannot::Capture.