= porter2stemmer
-Description goes here.
+==The Porter 2 stemmer
+This is the Porter 2 stemming algorithm, as described at
+http://snowball.tartarus.org/algorithms/english/stemmer.html
+The original paper is:
+
+Porter, 1980, "An algorithm for suffix stripping", _Program_, Vol. 14, no. 3, pp 130-137
+
+==Features of this implementation
+This stemmer is written in pure Ruby, making it easy to modify for language variants.
+For instance, the original Porter stemmer only works for American English and does
+not recognise British English's '-ise' as an alternate spelling of '-ize'. This
+implementation has been extended to handle correctly British English.
+
+This stemmer also features a comprehensive test set of over 29,000 words, taken from the
+{Porter 2 stemmer website}[http://snowball.tartarus.org/algorithms/english/stemmer.html].
+
+==Files
+Constants for the stemmer are in the Porter2 module.
+
+Procedures that implement the stemmer are added to the String class.
+
+The stemmer algorithm is implemented in the String#porter2_stem procedure.
+
+==Internationalisation
+There isn't much, as this is a stemmer that only works for English.
+
+The +gb_english+ flag to the various procedures allows the stemmer to treat the British
+English '-ise' the same as the American English '-ize'.
+
+==Longest suffixes
+Several places in the algorithm require matching the longest suffix of a word. The
+regexp engine in Ruby 1.9 seems to handle alterntives in regexps by finding the
+alternative that matches at the first position in the string. As we're only talking
+about suffixes, that first match is also the longest suffix. If the regexp engine changes,
+this behaviour may change and break the stemmer.
+
+==Usage
+Call the String#porter2_stem or String#stem methods on a string to return its stem
+ "consistency".stem # => "consist"
+ "knitting".stem # => "knit"
+ "articulated".stem # => "articul"
+ "nationalize".stem # => "nation"
+ "nationalise".stem # => "nationalis"
+ "nationalise".stem(true) # => "nation"
+
+==Author
+The Porter 2 stemming algorithm was developed by
+{Martin Porter}[http://snowball.tartarus.org/algorithms/english/stemmer.html].
+This implementation is by {Neil Smith}[http://www.njae.me.uk].
== Contributing to porter2stemmer
-
+
* Check out the latest master to make sure the feature hasn't been implemented or the bug hasn't been fixed yet
* Check out the issue tracker to make sure someone already hasn't requested it and/or contributed it
* Fork the project
projects / porter2stemmer.git / blobdiff