NAME

Data::Compare - compare perl data structures

SYNOPSIS

use Data::Compare;

my $h1 = { 'foo' => [ 'bar', 'baz' ],  'FOO' => [ 'one', 'two' ] };
my $h2 = { 'foo' => [ 'bar', 'barf' ], 'FOO' => [ 'one', 'two' ] };
my @a1 = ('one', 'two');
my @a2 = ('bar', 'baz');
my %v = ( 'FOO', \@a1, 'foo', \@a2 );

# simple procedural interface
print 'structures of $h1 and \%v are ',
  Compare($h1, \%v) ? "" : "not ", "identical.\n";

print 'structures of $h1 and $h2 are ',
  Compare($h1, $h2, { ignore_hash_keys => [qw(foo)] }) ? '' : 'not ',
  "close enough to identical.\n";

# OO usage
my $c = new Data::Compare($h1, \%v);
print 'structures of $h1 and \%v are ',
  $c->Cmp ? "" : "not ", "identical.\n";
# or
my $c = new Data::Compare;
print 'structures of $h and \%v are ',
  $c->Cmp($h1, \%v) ? "" : "not ", "identical.\n";

DESCRIPTION

Compare two perl data structures recursively. Returns 0 if the structures differ, else returns 1.

A few data types are treated as special cases:

Scalar::Properties objects

This has been moved into a plugin, although functionality remains the same as with the previous version. Full documentation is in Data::Compare::Plugins::Scalar::Properties.

Compiled regular expressions, eg qr/foo/

These are stringified before comparison, so the following will match:

$r = qr/abc/i;
$s = qr/abc/i;
Compare($r, $s);

and the following won't, despite them matching *exactly* the same text:

$r = qr/abc/i;
$s = qr/[aA][bB][cC]/;
Compare($r, $s);

Sorry, that's the best we can do.

CODE and GLOB references

These are assumed not to match unless the references are identical - ie, both are references to the same thing.

You may also customise how we compare structures by supplying options in a hashref as a third parameter to the Compare() function. This is not yet available through the OO-ish interface. These options will be in force for the *whole* of your comparison, so will apply to structures that are lurking deep down in your data as well as at the top level, so beware!

ignore_hash_keys

an arrayref of strings. When comparing two hashes, any keys mentioned in this list will be ignored.

CIRCULAR STRUCTURES

Comparing a circular structure to itself returns true:

$x = \$y;
$y = \$x;
Compare([$x, $y], [$x, $y]);

But comparing two different circular structures returns false:

$x = \$y;
$y = \$x;
Compare([$x, $y], [$y, $x]); # <-- note different order

And on a sort-of-related note, if you try to compare insanely deeply nested structures, the module will die. For this to affect you, you need to go around a hundred levels deep though, and if you do that you have bigger problems which I can't help you with ;-)

PLUGINS

The module takes plug-ins so you can provide specialised routines for comparing your own objects and data-types. For details see Data::Compare::Plugins.

A couple of functions are provided to examine what goodies have been made available through plugins:

plugins

Returns a structure (a hash ref) describing all the comparisons made available through plugins. This function is *not* exported, so should be called as Data::Compare::plugins(). It takes no parameters.

plugins_printable

Returns formatted text

BUGS

Plugin support is not quite finished (see the TODO file for details) but is usable. The missing bits are bells and whistles rather than core functionality.

AUTHOR

Fabien Tassin fta@sofaraway.org

Copyright (c) 1999-2001 Fabien Tassin. All rights reserved. This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

Seeing that Fabien seems to have disappeared, David Cantrell has become a co-maintainer so he can apply needed patches. The licence, of course, remains the same, and all communications about this module should be CCed to Fabien in case he ever returns and wants his baby back.

Portions, including plugins, copyright 2003-2004 David Cantrell david@cantrell.org.uk

SEE ALSO

perl(1), perlref(1)