NAME

Algorithm::LCS - Implementation of the longest common subsequence algorithm

SYNOPSIS

use Algorithm::LCS;

# regular usage
say lcs(<A B C D E F G>, <A C F H J>); # prints T<A C F>

# custom comparator via :compare
say lcs(<A B C>, <D C F>, :compare(&infix:<eq>));

# extra special custom comparison via :compare-i
my @a        = slurp('one.txt');
my @b        = slurp('two.txt');
my @a-hashed = @a.map({ hash-algorithm($_) });
my @b-hashed = @b.map({ hash-algorithm($_) });
say lcs(@a, @b, :compare-i({ @a-hashed[$^i] eqv @b-hashed[$^j] }));

DESCRIPTION

This module contains a single subroutine, lcs, that calculates the longest common subsequence between two sequences of data. lcs takes two lists as required parameters; you may also specify the comparison function (which defaults to eqv) via the &compare named parameter).

Sometimes you may want to maintain a parallel array of information to consult during calculation (for example, if you're comparing long lines of a file, and you'd like a speedup by comparing their hashes rather than their contents); for that, you may use the &compare-i named argumeny

SUBROUTINES

sub lcs

sub lcs(
    @a,
    @b,
    :&compare = Code.new,
    :&compare-i is copy
) returns Mu

Returns the longest common subsequence of two sequences of data.

class Mu $

The first sequence

class Mu $

The second sequence

class Mu $

The comparison function (defaults to C)

class Mu $

The compare-by-index function (defaults to using &compare)

SEE ALSO

Wikipedia article

AUTHORS

• Rob Hoelz

• Raku Community

COPYRIGHT AND LICENSE

Copyright (c) 2014 - 2017 Rob Hoelz

Copyright (c) 2024 Raku Community

This library is free software; you can redistribute it and/or modify it under the MIT license.