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יובל קוג'מן (Yuval Kogman) > Sub-SmartMatch > Sub::SmartMatch



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Module Version: 0.02   Source  


Sub::SmartMatch - Use smart matching to define multi subs


        use Sub::SmartMatch;

        use SmartMatch::Sugar qw(any);

        # variants will be tried in a given/when
        # clause in the order they are defined

        multi fact => [ 0 ], sub { 1 };

        multi fact => any, sub {
                my $n = shift;
                return $n * fact($n - 1);


This module provides Haskell/ML style subroutine variants based on Perl's smartmatch operator.

This doesn't do argument binding, just value matching.

To define methods use SmartMatch::Sugar's object test:

        multi new [ class ]  => sub {
                 # invoked as a class method

        multi new [ object ] => sub {
                # invoked as an object method
                # this should clone, i guess


exactly $case

This marks this case for exact matching. This means that it will match on \@_, not on the slice <[ @_[0 .. $#$case] ]>.

This only applies to cases which are array references themselves.

multi $name, $case, &body

Define a variant for the sub name $name.

$case will be smartmatched against an array reference of the arguments to the subroutine.

As a special case to allow variable arguments at the end of the list, if $case is an array reference it will only be matched against the slice of @_ with the corresponding number of elements, not all of @_. Use exactly to do a match on all of @_. This does not apply to an empty array (otherwise that would always match, instead of matching empty arrays).

multi_default $name, &body

Define the default for a multi sub. This variant is always tried last if no other variant matched.

def_multi $name, [ $case => &body, $case => &body, default => ... ]

Define a multi sub in one go.

        def_multi foo => (
                $case   => $body,
                ...     => ...,
                default => $default,


SmartMatch::Sugar, Sub::PatternMatch, perlsyn, Class::Multimethods::Pure


This module is maintained using Darcs. You can get the latest version from, and use darcs send to commit changes.


Yuval Kogman <>


        Copyright (c) 2008 Yuval Kogman. All rights reserved
        This program is free software; you can redistribute
        it and/or modify it under the same terms as Perl itself.
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