# 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].