Diff Longest Common Sub String Gem documentation

– The diff sniffing out texts every move

A resonably fast diff algoritm using longest common substrings that can also find text that has moved.

PositionRange is a library by the LogiLogi Foundation, extracted from www.logilogi.org (foundation.logilogi.org).

Usage

First require it.

$ irb

> require 'rubygems'
> require 'difflcs'

Then it can be used on any set of arrays, in this example 123456789 and 120678934, of which the first ‘12’ overlaps, ‘0’ is new, ‘34’ has moved to the end, and ‘6789’ overlaps too, but moved 2 positions to the left.

NOTE: They are arrays, not strings.

> DiffLCS.diff('123456789'.split(''), '120678934'.split('')) 
=> {
     :matched_old=>[0...2, 5...9, 2...4],
     :matched_new=>[0...2, 3...7, 7...9]
   }

As you see it can sniff out text that has moved too.

A minimum overlap size can be provided for speed purposes, and to prevent too many matches;

> DiffLCS.diff('123456789'.split(''), '120678934'.split(''), :minimum_lcs_size => 3)
=> {
     :matched_old => PositionRange::List.from_s('5,9'),
     :matched_new => PositionRange::List.from_s('3,7')
   }

Diff can be called directly on strings too, if ‘diff_l_c_s/string’ is required.

> require 'diff_l_c_s/string'
> '123'.diff('321')
=> {
     :matched_old=>[2...3, 1...2, 0...1],
     :matched_new=>[0...1, 1...2, 2...3]
   }

Installation

You can install Diff LCS with the following command:

% [sudo] gem install difflcs

The latest version of Diff LCS can also be downloaded at:

• rubyforge.org/frs/?group_id=7565

And then from its distribution directory installed with:

% [sudo] ruby install.rb

Support

The Diff LCS homepage is difflcs.rubyforge.org.

For the latest news on Diff LCS:

• foundation.logilogi.org/tags/DiffLCS

Feel free to submit commits or feature requests. If you send a patch, remember to update the corresponding unit tests.

This Documentation

This documentation can be browsed online at:

• difflcs.rubyforge.org

Copyrights

Diff LCS and these docs are Copyright © 2006-2009 The LogiLogi Foundation. Diff LCS is licensed under the GNU Lesser General Public License. These docs are available under the Creative Commons Attribution-Share Alike License.

You can use Diff LCS in an application that is not Free Software but Diff LCS itself remains Free Software.