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# -*- coding: utf-8 -*- |
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# Copyright 2014-2018 by Christopher C. Little. |
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# This file is part of Abydos. |
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# |
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# Abydos is free software: you can redistribute it and/or modify |
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# it under the terms of the GNU General Public License as published by |
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# the Free Software Foundation, either version 3 of the License, or |
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# (at your option) any later version. |
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# |
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# Abydos is distributed in the hope that it will be useful, |
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# but WITHOUT ANY WARRANTY; without even the implied warranty of |
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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# GNU General Public License for more details. |
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# |
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# You should have received a copy of the GNU General Public License |
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# along with Abydos. If not, see <http://www.gnu.org/licenses/>. |
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"""abydos.stemmer._snowball. |
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Snowball Stemmer base class |
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""" |
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from __future__ import ( |
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absolute_import, |
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division, |
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print_function, |
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unicode_literals, |
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) |
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from six.moves import range |
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from ._stemmer import _Stemmer |
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class _Snowball(_Stemmer): |
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"""Snowball stemmer base class.""" |
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_vowels = set('aeiouy') |
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_codanonvowels = set('\'bcdfghjklmnpqrstvz') |
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def _sb_r1(self, term, r1_prefixes=None): |
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"""Return the R1 region, as defined in the Porter2 specification. |
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Parameters |
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---------- |
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term : str |
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The term to examine |
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r1_prefixes : set |
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Prefixes to consider |
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Returns |
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------- |
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int |
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Length of the R1 region |
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""" |
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vowel_found = False |
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if hasattr(r1_prefixes, '__iter__'): |
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for prefix in r1_prefixes: |
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if term[: len(prefix)] == prefix: |
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return len(prefix) |
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for i in range(len(term)): |
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if not vowel_found and term[i] in self._vowels: |
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vowel_found = True |
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elif vowel_found and term[i] not in self._vowels: |
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return i + 1 |
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return len(term) |
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def _sb_r2(self, term, r1_prefixes=None): |
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"""Return the R2 region, as defined in the Porter2 specification. |
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Parameters |
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---------- |
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term : str |
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The term to examine |
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r1_prefixes : set |
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Prefixes to consider |
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Returns |
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------- |
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int |
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Length of the R1 region |
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""" |
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r1_start = self._sb_r1(term, r1_prefixes) |
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return r1_start + self._sb_r1(term[r1_start:]) |
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def _sb_ends_in_short_syllable(self, term): |
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"""Return True iff term ends in a short syllable. |
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(...according to the Porter2 specification.) |
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NB: This is akin to the CVC test from the Porter stemmer. The |
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description is unfortunately poor/ambiguous. |
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Parameters |
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---------- |
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term : str |
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The term to examine |
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Returns |
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------- |
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bool |
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True iff term ends in a short syllable |
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""" |
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if not term: |
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return False |
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if len(term) == 2: |
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if term[-2] in self._vowels and term[-1] not in self._vowels: |
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return True |
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elif len(term) >= 3: |
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if ( |
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term[-3] not in self._vowels |
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and term[-2] in self._vowels |
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and term[-1] in self._codanonvowels |
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): |
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return True |
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return False |
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def _sb_short_word(self, term, r1_prefixes=None): |
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"""Return True iff term is a short word. |
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(...according to the Porter2 specification.) |
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Parameters |
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---------- |
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term : str |
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The term to examine |
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r1_prefixes : set |
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Prefixes to consider |
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Returns |
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------- |
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bool |
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True iff term is a short word |
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""" |
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if self._sb_r1(term, r1_prefixes) == len( |
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term |
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) and self._sb_ends_in_short_syllable(term): |
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return True |
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return False |
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def _sb_has_vowel(self, term): |
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"""Return Porter helper function _sb_has_vowel value. |
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Parameters |
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---------- |
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term : str |
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The term to examine |
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Returns |
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------- |
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bool |
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True iff a vowel exists in the term (as defined in the Porter |
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stemmer definition) |
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""" |
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for letter in term: |
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if letter in self._vowels: |
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return True |
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return False |
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if __name__ == '__main__': |
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import doctest |
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doctest.testmod() |
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chrislit /
abydos
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