# Algorithm::DiffOld

Section: User Contributed Perl Documentation (3pm)
Updated: 2006-07-31

## NAME

Algorithm::DiffOld - Compute `intelligent' differences between two files / lists but use the old (<=0.59) interface.

## NOTE

This has been provided as part of the Algorithm::Diff package by Ned Konz. This particular module is ONLY for people who HAVE to have the old interface, which uses a comparison function rather than a key generating function.

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.

## SYNOPSIS

```  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,
},
\$comparison_function );

```

## COMPARISON FUNCTIONS

Each of the main routines should be passed a comparison function. If you aren't passing one in, use Algorithm::Diff instead.

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.

## Index

NAME
NOTE
SYNOPSIS
COMPARISON FUNCTIONS