From: Steven M. Haflich
Subject: CL implementation of the Porter Stemming Algorithm
Date: Thu, 28 Mar 2002 00:00:01 +0000
Message-ID: <3CA258C3.CBF06036@franz.com>

I needed a word stemmer for a certain project so did a port of
Martin Porter's word stemmer to Common Lisp.  Martin has graciously
taken back my code and made it available along with various other
language versions on the web site he maintains for this algorithm:
http://www.tartarus.org/~martin/PorterStemmer

    The Porter stemming algorithm (or �Porter stemmer�) is a
    process for removing the commoner morphological and inflexional
    endings from words in English. Its main use is as part of a
    term normalisation process that is usually done when setting up
    Information Retrieval systems.

    The algorithm was originally described in Porter, M.F., 1980,
    An algorithm for suffix stripping, Program, 14(3) :130-137.
    It has since been reprinted in Sparck     Jones, Karen, and
    Peter Willet, 1997, Readings in Information Retrieval, San
    Francisco: Morgan Kaufmann, ISBN 1-55860-454-4.
    ...
    All these encodings of the algorithm can be used free of charge
    for any purpose.