Stemmable

# File lib/stemmer/porter.rb, line 96
def stem_porter

  # make a copy of the given object and convert it to a string.

  w = self.dup.to_str
  
  return w if w.length < 3
  
  # now map initial y to Y so that the patterns never treat it as vowel

  w[0] = 'Y' if w[0] == yy
  
  # Step 1a

  if w =~ /(ss|i)es$/
    w = $` + $1
  elsif w =~ /([^s])s$/ 
    w = $` + $1
  end

  # Step 1b

  if w =~ /eed$/
    w.chop! if $` =~ MGR0 
  elsif w =~ /(ed|ing)$/
    stem = $`
    if stem =~ VOWEL_IN_STEM 
      w = stem
      case w
      when /(at|bl|iz)$/             then w << "e"
      when /([^aeiouylsz])\11$$/       then w.chop!
      when /^#{CC}#{V}[^aeiouwxy]$/ then w << "e"
      end
    end
  end

  if w =~ /y$/ 
    stem = $`
    w = stem + "i" if stem =~ VOWEL_IN_STEM 
  end

  # Step 2

  if w =~ SUFFIX_1_REGEXP
    stem = $`
    suffix = $1
    # print "stem= " + stem + "\n" + "suffix=" + suffix + "\n"

    if stem =~ MGR0
      w = stem + STEP_2_LIST[suffix]
    end
  end

  # Step 3

  if w =~ /(icate|ative|alize|iciti|ical|ful|ness)$/
    stem = $`
    suffix = $1
    if stem =~ MGR0
      w = stem + STEP_3_LIST[suffix]
    end
  end

  # Step 4

  if w =~ SUFFIX_2_REGEXP
    stem = $`
    if stem =~ MGR1
      w = stem
    end
  elsif w =~ /(s|t)(ion)$/
    stem = $` + $1
    if stem =~ MGR1
      w = stem
    end
  end

  #  Step 5

  if w =~ /e$/ 
    stem = $`
    if (stem =~ MGR1) ||
        (stem =~ MEQ1 && stem !~ /^#{CC}#{V}[^aeiouwxy]$/)
      w = stem
    end
  end

  if w =~ /ll$/ && w =~ MGR1
    w.chop!
  end

  # and turn initial Y back to y

  w[0] = 'y' if w[0] == YY

  w
end