Class PorterStemmer

The main part of the stemming algorithm starts here.
b is a buffer holding a word to be stemmed. The letters are in b[k0],
b[k0+1] ... ending at b[k]. In fact k0 = 0 in this demo program. k is
readjusted downwards as the stemming progresses. Zero termination is
not in fact used in the algorithm.

Note that only lower case sequences are stemmed. Forcing to lower case
should be done before stem(...) is called.

Overrides: object.__init__

m() measures the number of consonant sequences between k0 and j.
if c is a consonant sequence and v a vowel sequence, and <..>
indicates arbitrary presence,

   <c><v>       gives 0
   <c>vc<v>     gives 1
   <c>vcvc<v>   gives 2
   <c>vcvcvc<v> gives 3
   ....

cvc(i) is TRUE <=>

a) ( --NEW--) i == 1, and p[0] p[1] is vowel consonant, or

b) p[i - 2], p[i - 1], p[i] has the form consonant -
   vowel - consonant and also if the second c is not w, x or y. this
   is used when trying to restore an e at the end of a short word.
   e.g.

       cav(e), lov(e), hop(e), crim(e), but
       snow, box, tray.        

step1ab() gets rid of plurals and -ed or -ing. e.g.

caresses  ->  caress
ponies    ->  poni
sties     ->  sti
tie       ->  tie        (--NEW--: see below)
caress    ->  caress
cats      ->  cat

feed      ->  feed
agreed    ->  agree
disabled  ->  disable

matting   ->  mat
mating    ->  mate
meeting   ->  meet
milling   ->  mill
messing   ->  mess

meetings  ->  meet

step1c() turns terminal y to i when there is another vowel in the stem.
--NEW--: This has been modified from the original Porter algorithm so that y->i
is only done when y is preceded by a consonant, but not if the stem
is only a single consonant, i.e.

   (*c and not c) Y -> I

So 'happy' -> 'happi', but
  'enjoy' -> 'enjoy'  etc

This is a much better rule. Formerly 'enjoy'->'enjoi' and 'enjoyment'->
'enjoy'. Step 1c is perhaps done too soon; but with this modification that
no longer really matters.

Also, the removal of the vowelinstem(z) condition means that 'spy', 'fly',
'try' ... stem to 'spi', 'fli', 'tri' and conflate with 'spied', 'tried',
'flies' ...

step2() maps double suffices to single ones.
so -ization ( = -ize plus -ation) maps to -ize etc. note that the
string before the suffix must give m() > 0.

step3() dels with -ic-, -full, -ness etc. similar strategy to step2.

In stem(p,i,j), p is a char pointer, and the string to be stemmed
is from p[i] to p[j] inclusive. Typically i is zero and j is the
offset to the last character of a string, (p[j+1] == ''). The
stemmer adjusts the characters p[i] ... p[j] and returns the new
end-point of the string, k. Stemming never increases word length, so
i <= k <= j. To turn the stemmer into a module, declare 'stem' as
extern, and delete the remainder of this file.

Strip affixes from the token and return the stem.

Parameters:

• token - The token that should be stemmed.

Overrides: api.StemmerI.stem

(inherited documentation)

repr(x)

Overrides: object.__repr__

(inherited documentation)