Because each of the lines in one array have to be compared with each of the lines in the other array, this does M*N comparisions. This can be very slow. I clocked it at taking 18 times as long as the stock version of Algorithm::Diff for a 4000-line file. It will get worse quadratically as array sizes increase.
use Algorithm::DiffOld qw(diff LCS traverse_sequences); @lcs = LCS( \@seq1, \@seq2, $comparison_function ); $lcsref = LCS( \@seq1, \@seq2, $comparison_function ); @diffs = diff( \@seq1, \@seq2, $comparison_function ); traverse_sequences( \@seq1, \@seq2, { MATCH => $callback, DISCARD_A => $callback, DISCARD_B => $callback, }, $comparison_function );
These functions should return a true value when two items should compare as equal.
For instance,
@lcs = LCS( \@seq1, \@seq2, sub { my ($a, $b) = @_; $a eq $b } );
but if that is all you're doing with your comparison function, just use Algorithm::Diff and let it do this (this is its default).
Or:
sub someFunkyComparisonFunction { my ($a, $b) = @_; $a =~ m{$b}; } @diffs = diff( \@lines, \@patterns, \&someFunkyComparisonFunction );
which would allow you to diff an array @lines which consists of text lines with an array @patterns which consists of regular expressions.
This is actually the reason I wrote this version --- there is no way to do this with a key generation function as in the stock Algorithm::Diff.