### ----------------------------------------------------
### -- Algorithm::LCS
### -- Licenses: MIT
### -- Authors: Rob Hoelz, Raku Community
### -- File: README.md
### ----------------------------------------------------
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NAME
====

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

SYNOPSIS
========

```raku
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

```raku
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<eqv>)

class Mu $
----------

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

SEE ALSO
========

[Wikipedia article](http://en.wikipedia.org/wiki/Longest_common_subsequence_problem)

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.



