NAME

Sub::Multi::Tiny - Multisubs/multimethods (multiple dispatch) yet another way!

SYNOPSIS

{
    package main::my_multi;     # We're making main::my_multi()
    use Sub::Multi::Tiny qw($foo $bar);     # All possible params

    sub first :M($foo, $bar) { # sub's name will be ignored
        return $foo ** $bar;
    }

    sub second :M($foo) {
        return $foo + 42;
    }

}

# Back in package main, my_multi() is created just before the run phase.
say my_multi(2, 5);     # -> 32
say my_multi(1295);     # -> 1337

Limitation: At present, dispatch is solely by arity, and only one candidate can have each arity. This limitation will be removed in the future.

DESCRIPTION

Sub::Multi::Tiny is a library for making multisubs, aka multimethods, aka multiple-dispatch subroutines.

FUNCTIONS

import

Sets up the package that uses it to define a multisub. The parameters are all the parameter variables that the multisubs will use. import creates these as package variables so that they can be used unqualified in the multisub implementations.

CUSTOM DISPATCH

This module includes a default dispatcher (implemented in Sub::Multi::Tiny::DefaultDispatcher. To use a different dispatcher, define or import a sub MakeDispatcher() into the package before compilation ends. That sub will be called to create the dispatcher. For example:

{
    package main::foo;
    use Sub::Multi::Tiny;
    sub MakeDispatcher { return sub { ... } }
}

or

{
    package main::foo;
    use Sub::Multi::Tiny;
    use APackageThatImportsMakeDispatcherIntoMainFoo;
}

DEBUGGING

For extra debug output, set "$VERBOSE" in Sub::Multi::Tiny::Util to a positive integer. This has to be set at compile time to have any effect. For example, before creating any multisubs, do:

use Sub::Multi::Tiny::Util '*VERBOSE';
BEGIN { $VERBOSE = 2; }

RATIONALE

• To be able to use multisubs in pre-5.14 Perls with only built-in language facilities. This will help me make my own modules backward compatible with those Perls.
• To learn how it's done! :)

SEE ALSO

I looked at these but decided not to use them for the following reasons:

• Class::Multimethods

  I wanted a syntax that used normal sub definitions as much as possible. Also, I was a bit concerned by LPALMER's experience that it "does what you don't want sometimes without saying a word" ("Semantics" in Class::Multimethods::Pure).

  Other than that, I think this looks pretty decent (but haven't tried it).

• Class::Multimethods::Pure

  Same desire for sub syntax. Additionally, the last update was in 2007, and the maintainer hasn't uploaded anything since. Other than that, I think this also looks like a decent option (but haven't tried it).

• Dios

  This is a full object system, which I do not need in my use case.

• Logic

  This one is fairly clean, but uses a source filter. I have not had much experience with source filters, so am reluctant.

• Kavorka::Manual::MultiSubs (and Moops)

  Requires Perl 5.14+.

• MooseX::MultiMethods

  I am not ready to move to full Moose!

• MooseX::Params

  As above.

• Sub::Multi

  The original inspiration for this module, whence this module's name. Sub::Multi uses coderefs, and I wanted a syntax that used normal sub definitions as much as possible.

• Sub::SmartMatch

  This one looks very interesting, but I haven't used smartmatch enough to be fully comfortable with it.

SUPPORT

You can find documentation for this module with the perldoc command.

perldoc Sub::Multi::Tiny

You can also look for information at:

• GitHub: The project's main repository and issue tracker

  https://github.com/cxw42/Sub-Multi-Tiny

• MetaCPAN

  Sub::Multi::Tiny

• This distribution

  See the tests in the t/ directory distributed with this software for examples.

BUGS

This isn't Damian code ;) .

AUTHOR

Chris White cxw@cpan.org

LICENSE

Copyright (C) 2019 Chris White cxw@cpan.org

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.