This is an implementation of the standard Unix tool diff in Common
Lisp.  The diff0.lisp file uses a simple but inefficient recursive
algorithm which is O(nm) in time and space to find the longest common
subsequence between two files.  The diff1.lisp file implements the
algorithm described in ``An algorithm for differential file
comparison'' by J. W. Hunt and M. D. McIllroy which worst case
behavior is O(mnlog m) in time and O(mn) in space.  But in practice
the complexity is linear in both time and space.

See: http://www.cs.dartmouth.edu/~doug/diff.ps