May 26, 2018

Support multimethods and function overloading in Perl

The ClassMultimethod module exports a subroutine &multimethod that can be used to declare other subroutines that are dispatched using a algorithm different from the normal Perl subroutine or method dispatch mechanism.

Normal Perl subroutines are dispatched by finding the appropriately-named subroutine in the current or specified package and calling that. Normal Perl methods are dispatched by attempting to find the appropriately-named subroutine in the package into which the invoking object is blessed or, failing that, recursively searching for it in the packages listed in the appropriate @ISA arrays.

ClassMultimethods multimethods are dispatched quite differently. The dispatch mechanism looks at the classes or types of each argument to the multimethod by calling ref on each and determines the “closest” matching variant of the multimethod, according to the argument types specified in the variants’ definitions see “Finding the “nearest” multimethod” for a definition of “closest”.

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