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+# coding: utf-8
+
+# ==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].
+