def stem(self, words):
        """
        Use the porter stemmer to generate consistent forms of
        words, e.g.::

            from walrus.search.utils import PorterStemmer
            stemmer = PorterStemmer()
            for word in ['faith', 'faiths', 'faithful']:
                print s.stem(word, 0, len(word) - 1)

            # Prints:
            # faith
            # faith
            # faith
        """
        stemmer = PorterStemmer()
        _stem = stemmer.stem
        for word in words:
            yield _stem(word, 0, len(word) - 1)
Use the porter stemmer to generate consistent forms of
        words, e.g.::

            from walrus.search.utils import PorterStemmer
            stemmer = PorterStemmer()
            for word in ['faith', 'faiths', 'faithful']:
                print s.stem(word, 0, len(word) - 1)

            # Prints:
            # faith
            # faith
            # faith