X-Git-Url: https://git.njae.me.uk/?a=blobdiff_plain;f=README.rdoc;h=4f3a355bcd82fd15ce8cc50a90a9767c0d54f1de;hb=refs%2Fheads%2Fmaster;hp=4a991e12a4a6353452bfa8d5296c534d942dfd4e;hpb=cfc1c3309c8c78411683697836307ee18f20ea1d;p=porter2stemmer.git

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 = 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