NAME

Match::Smart - best-guess matching of two scalars

SYNOPSIS

use Match::Smart qw/ smart_match /;

if (smart_match( $user, qr/^dan/ )) {
   print "You might be a dan\n";
}

if (smart_match( $amount, sub { $_[0] < 10} )) {
   print "$amount is less than 10\n";
}

DESCRIPTION

C<Match::Smart> provides a easy means of testing whether two scalars match.
A best guess on how they should be compared is made, based on the types of
the two scalars.

The means of matching is based heavily on the Apocalypse 4, Perl 6 document
by Larry Wall.

EXPORT

Nothing is exported by default. The C<smart_match()> subroutine can be
exported if desired.

FUNCTIONS

smart_match($val1, $val2)

Attempts to do the right thing in I<matching> the two given values. Returns
true if the two values I<match>, false otherwise.

If both values are references, referring to the same thing, they are assumed
to match.

The table below describes how the comparisons are performed. Those described
using C<grep> only do so for conciseness. The implementation uses C<for>
loops to allow short-circuiting as soon as a match is determined.

The order in which the values are passed to C<smart_match()> only affects
the return value when comparing two CODE references. Therefore, the table
below only shows half of the necessary comparisons (those missing can be
inferred).

Those noted as '-' are not currently defined and will result in fatal
run-time exceptions.


   $val1    $val2    true if ...
   =====    =====    ===========

   ARRAY    ARRAY    any in @{$val1} smart_match any in @{$val2}
   ARRAY    CODE     $val2->(@{$val1})
   ARRAY    HASH     grep { $val2->{$_} } @{$val1}
   ARRAY    NUMBER   $val1->[$val2]
   ARRAY    OBJECT   grep { smart_match($_, $val2)    } @{$val1}
   ARRAY    REF      grep { smart_match($_, ${$val2}) } @{$val1}
   ARRAY    REGEXP   grep { smart_match($_, $val2)    } @{$val1}
   ARRAY    SCALAR   grep { smart_match($_, ${$val2}) } @{$val1}
   ARRAY    STRING   grep { smart_match($_, $val2)    } @{$val1}
   ARRAY    UNDEF    grep { smart_match($_, $val2)    } @{$val1}

   CODE     CODE     $val1->(&{$val2})
   CODE     HASH     $val1->(%{$val2})
   CODE     NUMBER   $val1->($val2)
   CODE     OBJECT   $val1->($val2)
   CODE     REF      smart_match($val1, ${$val2})
   CODE     REGEXP   $val1->($val2)
   CODE     SCALAR   smart_match($val1, ${$val2})
   CODE     STRING   $val1->($val2)
   CODE     UNDEF    $val1->($val2)

   HASH     HASH     grep { exists $val1->{$_} } keys %{$val2}
   HASH     NUMBER   $val1->{$val2}
   HASH     OBJECT   -
   HASH     REF      smart_match($val1, ${$val2})
   HASH     REGEXP   grep { $_ =~ $val2 } keys %{$val1}
   HASH     SCALAR   smart_match($val1, ${$val2})
   HASH     STRING   $val1->{$val2}
   HASH     UNDEF    -

   NUMBER   NUMBER   $val1 == $val2
   NUMBER   OBJECT   -
   NUMBER   REF      smart_match($val1, ${$val2})
   NUMBER   REGEXP   $val1 =~ $val2
   NUMBER   SCALAR   smart_match($val1, ${$val2})
   NUMBER   STRING   $val1 == $val2
   NUMBER   UNDEF    ** ALWAYS FALSE **

   OBJECT   OBJECT   $val1 == $val2
   OBJECT   REF      smart_match($val1, ${$val2})
   OBJECT   REGEXP   -
   OBJECT   SCALAR   smart_match($val1, ${$val2})
   OBJECT   STRING   $val1->can($val2) && $val1->$val2
   OBJECT   UNDEF    ** ALWAYS FALSE **

   REF      REF      smart_match(${$val1}, ${$val2})
   REF      REGEXP   smart_match(${$val1}, $val2)
   REF      SCALAR   smart_match(${$val1}, ${$val2})
   REF      STRING   smart_match(${$val1}, $val2)
   REF      UNDEF    smart_match(${$val1}, $val2)

   REGEXP   REGEXP   $val1 eq $val2
   REGEXP   SCALAR   smart_match($val1, ${$val2})
   REGEXP   STRING   $val2 =~ $val1
   REGEXP   UNDEF    ** ALWAYS FALSE **

   SCALAR   SCALAR   smart_match(${$val1}, ${$val2})
   SCALAR   STRING   smart_match(${$val1}, $val2)
   SCALAR   UNDEF    smart_match(${$val1}, $val2)

   STRING   STRING   $val1 eq $val2
   STRING   UNDEF    ** ALWAYS FALSE **

   UNDEF    UNDEF    ** ALWAYS TRUE **

TO DO

- handle GLOB and LVALUE ref types

- provide a means of registering comparisons for specific Object types (call Class->smart_match() method to get class to fill in requirements)

- allow the comparison methods to be overridden

SEE ALSO

Apocalypse 4: http://www.perl.com/pub/a/2002/01/15/apo4.html?page=2

AUTHOR

Daniel B. Boorstein, <danboo@cpan.org>

COPYRIGHT AND LICENSE

Copyright 2004 by Daniel B. Boorstein

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