Diff::LCS is a port of Algorithm::Diff that uses the McIlroy-Hunt longest common subsequence (LCS) algorithm to compute intelligent differences between two sequenced enumerable containers. The implementation is based on Mario I. Wolczko's Smalltalk version (1.2, 1993) and Ned Konz's Perl version (Algorithm::Diff).
This release is version 1.1.2, fixing an htmldiff bug in 1.1.1. Version 1.1.0 added new features, including the ability to #patch and #unpatch changes as well as a new contextual diff callback, Diff::LCS::ContextDiffCallbacks, that should improve the context sensitivity of patching.
Using this module is quite simple. By default, Diff::LCS does not extend objects with the Diff::LCS interface, but will be called as if it were a function:
seq1 = %w(a b c e h j l m n p)
seq2 = %w(b c d e f j k l m r s t)
lcs = Diff::LCS.LCS(seq1, seq2)
diffs = Diff::LCS.diff(seq1, seq2)
sdiff = Diff::LCS.sdiff(seq1, seq2)
seq = Diff::LCS.traverse_sequences(seq1, seq2, callback_obj)
bal = Diff::LCS.traverse_balanced(seq1, seq2, callback_obj)
seq2 == Diff::LCS.patch!(seq1, diffs)
seq1 == Diff::LCS.unpatch!(seq2, diffs)
seq2 == Diff::LCS.patch!(seq1, sdiff)
seq1 == Diff::LCS.unpatch!(seq2, sdiff)
Objects can be extended with Diff::LCS:
lcs = seq1.lcs(seq2)
diffs = seq1.diff(seq2)
sdiff = seq1.sdiff(seq2)
seq = seq1.traverse_sequences(seq2, callback_obj)
bal = seq1.traverse_balanced(seq2, callback_obj)
seq2 == seq1.patch!(diffs)
seq1 == seq2.unpatch!(diffs)
seq2 == seq1.patch!(sdiff)
seq1 == seq2.unpatch!(sdiff)
By requiring 'diff/lcs/array' or 'diff/lcs/string', Array or String will be extended for use this way.
# Copyright 2004 Austin Ziegler <firstname.lastname@example.org>
# adapted from:
# Algorithm::Diff (Perl) by Ned Konz <email@example.com>
# Smalltalk by Mario I. Wolczko <firstname.lastname@example.org>
# implements McIlroy-Hunt diff algorithm
# This program is free software. It may be redistributed and/or modified
# under the terms of the GPL version 2 (or later), the Perl Artistic
# licence, or the Ruby licence.
# $Id: README,v 1.5 2004/08/08 20:33:09 austin Exp $
 This library is called Diff::LCS because there are
multiple Ruby libraries called Algorithm::Diff
maintained by other authors.
 By sequenced enumerable, I mean that the order of
enumeration is predictable and consistent for the same
set of data. While it is theoretically possible to
generate a diff for unordereded hash, it will only be
meaningful if the enumeration of the hashes is
consistent. In general, this will mean that containers
that behave like String or Array will perform best.