NAME

       Array::Compare - Perl extension for comparing arrays.

SYNOPSIS

         use Array::Compare;

         my $comp1 = Array::Compare->new;
         $comp->Sep('|');
         $comp->Skip({3 => 1, 4 => 1});
         $comp->WhiteSpace(0);
         $comp->Case(1);

         my $comp2 = Array::Compare->new(Sep => '|',
                                         WhiteSpace => 0,
                                         Case => 1,
                                         Skip => {3 => 1, 4 => 1});

         my @arr1 = 0 .. 10;
         my @arr2 = 0 .. 10;

         $comp1->compare(\@arr1, \@arr2);
         $comp2->compare(\@arr1, \@arr2);

DESCRIPTION

       If you have two arrays and you want to know if they are the same or different, then
       Array::Compare will be useful to you.

       All comparisons are carried out via a comparator object. In the simplest usage, you can
       create and use a comparator object like this:

         my @arr1 = 0 .. 10;
         my @arr2 = 0 .. 10;

         my $comp = Array::Compare->new;

         if ($comp->compare(\@arr1, \@arr2)) {
           print "Arrays are the same\n";
         } else {
           print "Arrays are different\n";
         }

       Notice that you pass references to the two arrays to the comparison method.

       Internally the comparator compares the two arrays by using "join" to turn both arrays into
       strings and comparing the strings using "eq". In the joined strings, the elements of the
       original arrays are separated with the "^G" character. This can cause problems if your
       array data contains "^G" characters as it is possible that two different arrays can be
       converted to the same string.

       To avoid this, it is possible to override the default separator character, either by
       passing and alternative to the "new" function

         my $comp = Array::Compare->new(Sep => '|');

       or by changing the seperator for an existing comparator object

         $comp->Sep('|');

       In general you should choose a separator character that won't appear in your data.

       You can also control whether or not whitespace within the elements of the arrays should be
       considered significant when making the comparison.  The default is that all whitespace is
       significant. The alternative is for all consecutive white space characters to be converted
       to a single space for the pruposes of the comparison. Again, this can be turned on when
       creating a comparator object:

         my $comp = Array::Compare->new(WhiteSpace => 0);

       or by altering an existing object:

         $comp->WhiteSpace(0);

       You can also control whether or not the case of the data is significant in the comparison.
       The default is that the case of data is taken into account. This can be changed in the
       standard ways when creating a new comparator object:

         my $comp = Array::Compare->new(Case => 0);

       or by altering an existing object:

         $comp->Case(0);

       In addition to the simple comparison described above (which returns true if the arrays are
       the same and false if they're different) there is also a full comparison which returns a
       list containing the indexes of elements which differ between the two arrays. If the arrays
       are the same it returns an empty list. In scalar context the full comparison returns the
       length of this list (i.e. the number of elements that differ). You can access the full
       comparision in two ways. Firstly, there is a "DefFull" attribute. If this is "true" then a
       full comparison if carried out whenever the "compare" method is called.

         my $comp = Array::Compare->new(DefFull => 1);
         $comp->compare(\@arr1, \@arr2); # Full comparison

         $comp->DefFull(0);
         $comp->compare(\@arr1, \@arr2); # Simple comparison

         $comp->DefFull(1);
         $comp->compare(\@arr1, \@arr2); # Full comparison again

       Secondly, you can access the full comparison method directly

         $comp->full_compare(\@arr1, \@arr2);

       For symmetry, there is also a direct method to use to call the simple comparison.

         $comp->simple_compare(\@arr1, \@arr2);

       The final complication is the ability to skip elements in the comparison.  If you know
       that two arrays will always differ in a particular element but want to compare the arrays
       ignoring this element, you can do it with Array::Compare without taking array slices. To
       do this, a comparator object has an optional attribute called "Skip" which is a reference
       to a hash. The keys in this hash are the indexes of the array elements and the values
       should be any true value for elements that should be skipped.

       For example, if you want to compare two arrays, ignoring the values in elements two and
       four, you can do something like this:

         my %skip = (2 => 1, 4 => 1);
         my @a = (0, 1, 2, 3, 4, 5);
         my @b = (0, 1, X, 3, X, 5);

         my $comp = Array::Compare->new(Skip => \%skip);

         $comp->compare(\@a, \@b);

       This should return true, as we are explicitly ignoring the columns which differ.

       Of course, having created a comparator object with no skip hash, it is possible to add one
       later:

         $comp->Skip({1 => 1, 2 => 1});

       or:

         my %skip = (1 => 1, 2 => 2);
         $comp->Skip(\%skip);

       To reset the comparator so that no longer skips elements, set the skip hash to an empty
       hash.

         $comp->Skip({});

       You can also check to see if one array is a permutation of another, i.e.  they contain the
       same elements but in a different order.

         if ($comp->perm(\@a, \@b) {
           print "Arrays are perms\n";
         else {
           print "Nope. Arrays are completely different\n";
         }

       In this case the values of "WhiteSpace" and "Case" are still used, but "Skip" is ignored
       for, hopefully, obvious reasons.

METHODS

   new [ %OPTIONS ]
       Constructs a new comparison object.

       Takes an optional hash containing various options that control how comparisons are carried
       out. Any omitted options take useful defaults.

       Sep This is the value that is used to separate fields when the array is joined into a
           string. It should be a value which doesn't appear in your data.  Default is '^G'.

       WhiteSpace
           Flag that indicates whether or not whitespace is significant in the comparison. If
           this value is false then all multiple whitespace characters are changed into a single
           space before the comparison takes place. Default is 1 (whitespace is significant).

       Case
           Flag that indicates whther or not the case of the data should be significant in the
           comparison. Default is 1 (case is significant).

       Skip
           a reference to a hash which contains the numbers of any columns that should be skipped
           in the comparison. Default is an empty hash (all columns are significant).

       DefFull
           Flag which indicates whether the default comparison is simple (just returns true if
           the arrays are the same or false if they're not) or full (returns an array containing
           the indexes of the columns that differ). Default is 0 (simple comparison).

   compare_len \@ARR1, \@ARR2
       Very simple comparison. Just checks the lengths of the arrays are the same.

   compare \@ARR1, \@ARR2
       Compare the values in two arrays and return a data indicating whether the arrays are the
       same. The exact return values differ depending on the comparison method used. See the
       descriptions of simple_compare and full_compare for details.

       Uses the value of DefFull to determine which comparison routine to use.

   simple_compare \@ARR1, \@ARR2
       Compare the values in two arrays and return a flag indicating whether or not the arrays
       are the same.

       Returns true if the arrays are the same or false if they differ.

       Uses the values of 'Sep', 'WhiteSpace' and 'Skip' to influence the comparison.

   full_compare \@ARR1, \@ARR2
       Do a full comparison between two arrays.

       Checks each individual column. In scalar context returns the number of columns that differ
       (zero if the arrays are the same). In list context returns an list containing the indexes
       of the columns that differ (an empty list if the arrays are the same).

       Uses the values of 'Sep' and 'WhiteSpace' to influence the comparison.

       Note: If the two arrays are of different lengths then this method just returns the indexes
       of the elements that appear in one array but not the other (i.e. the indexes from the
       longer array that are beyond the end of the shorter array). This might be a little
       counter-intuitive.

   perm \@ARR1, \@ARR2
       Check to see if one array is a permutation of the other (i.e. contains the same set of
       elements, but in a different order).

       We do this by sorting the arrays and passing references to the assorted versions to
       simple_compare. There are also some small changes to simple_compare as it should ignore
       the Skip hash if we are called from perm.

AUTHOR

       Dave Cross <dave@mag-sol.com>

SEE ALSO

       perl(1).

COPYRIGHT AND LICENSE

       Copyright (C) 2000-2005, Magnum Solutions Ltd.  All Rights Reserved.

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