420 lines
14 KiB
PHP
420 lines
14 KiB
PHP
<?php
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function GetStem($word) {
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# A list of irregular plurals not supported by Porter's algorithm.
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$irregular=array ( 'alumni' => 'alumnus', 'cacti' => 'cactus', 'foci' => 'focus', 'focuses' => 'focuses', 'fungi' => 'funguses', 'nuclei' => 'nucleus', 'radii' => 'radius', 'stimuli' => 'stimulus', 'axes' => 'axis', 'analyses' => 'analysis', 'bases' => 'basis', 'crises' => 'crisis', 'diagnoses' => 'diagnosis', 'ellipses' => 'ellipsis', 'hypotheses' => 'hypothesis', 'oases' => 'oasis', 'paralyses' => 'paralysis', 'parentheses' => 'parenthesis', 'syntheses' => 'synthesis', 'synopses' => 'synopsis', 'theses' => 'thesis', 'appendices' => 'appendix', 'indeces' => 'index', 'indexes' => 'index', 'matrixes' => 'matrix', 'beaux' => 'beau', 'bureaus' => 'bureau', 'bureaux' => 'bureau', 'tableaux' => 'tableau', 'tableaus' => 'tableau', 'children' => 'child', 'men' => 'man', 'oxen' => 'ox', 'women' => 'woman', 'bacteria' => 'bacterium', 'corpora' => 'corpus', 'criteria' => 'criterion', 'curricula' => 'curriculum', 'data' => 'datum', 'genera' => 'genus', 'media' => 'medium', 'memoranda' => 'memorandum', 'phenomena' => 'phenomenon', 'strata' => 'stratum', 'deer' => 'deer', 'feet' => 'foot', 'geese' => 'goose', 'teeth' => 'tooth', 'antennae','antennas' => 'antenna', 'formulae' => 'formula', 'formulas' => 'formula', 'nebulae' => 'nebula', 'vertebrae' => 'vertebra', 'vitae' => 'vita', 'lice' => 'louse', 'mice' => 'mouse' );
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if (array_key_exists($word."",$irregular)) { $word=$irregular[$word]; } # Replace, then still go through Porter
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return PorterStemmer::Stem($word);
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}
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/**
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* Copyright (c) 2005 Richard Heyes (http://www.phpguru.org/)
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*
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* All rights reserved.
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*
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* This script is free software.
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*/
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/**
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* PHP5 Implementation of the Porter Stemmer algorithm. Certain elements
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* were borrowed from the (broken) implementation by Jon Abernathy.
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*
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* Usage:
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*
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* $stem = PorterStemmer::Stem($word);
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*
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* How easy is that?
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*/
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class PorterStemmer
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{
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/**
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* Regex for matching a consonant
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* @var string
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*/
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private static $regex_consonant = '(?:[bcdfghjklmnpqrstvwxz]|(?<=[aeiou])y|^y)';
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/**
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* Regex for matching a vowel
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* @var string
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*/
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private static $regex_vowel = '(?:[aeiou]|(?<![aeiou])y)';
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/**
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* Stems a word. Simple huh?
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*
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* @param string $word Word to stem
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* @return string Stemmed word
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*/
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public static function Stem($word)
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{
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if (strlen($word) <= 2) {
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return $word;
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}
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$word = self::step1ab($word);
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$word = self::step1c($word);
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$word = self::step2($word);
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$word = self::step3($word);
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$word = self::step4($word);
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$word = self::step5($word);
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return $word;
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}
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/**
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* Step 1
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*/
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private static function step1ab($word)
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{
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// Part a
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if (substr($word, -1) == 's') {
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self::replace($word, 'sses', 'ss')
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OR self::replace($word, 'ies', 'i')
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OR self::replace($word, 'ss', 'ss')
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OR self::replace($word, 's', '');
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}
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// Part b
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if (substr($word, -2, 1) != 'e' OR !self::replace($word, 'eed', 'ee', 0)) { // First rule
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$v = self::$regex_vowel;
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// ing and ed
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if ( preg_match("#$v+#", substr($word, 0, -3)) && self::replace($word, 'ing', '')
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OR preg_match("#$v+#", substr($word, 0, -2)) && self::replace($word, 'ed', '')) { // Note use of && and OR, for precedence reasons
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// If one of above two test successful
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if ( !self::replace($word, 'at', 'ate')
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AND !self::replace($word, 'bl', 'ble')
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AND !self::replace($word, 'iz', 'ize')) {
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// Double consonant ending
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if ( self::doubleConsonant($word)
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AND substr($word, -2) != 'll'
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AND substr($word, -2) != 'ss'
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AND substr($word, -2) != 'zz') {
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$word = substr($word, 0, -1);
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} elseif (self::m($word) == 1 AND self::cvc($word)) {
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$word .= 'e';
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}
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}
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}
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}
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return $word;
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}
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/**
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* Step 1c
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*
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* @param string $word Word to stem
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*/
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private static function step1c($word)
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{
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$v = self::$regex_vowel;
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if (substr($word, -1) == 'y' && preg_match("#$v+#", substr($word, 0, -1))) {
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self::replace($word, 'y', 'i');
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}
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return $word;
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}
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/**
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* Step 2
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*
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* @param string $word Word to stem
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*/
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private static function step2($word)
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{
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switch (substr($word, -2, 1)) {
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case 'a':
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self::replace($word, 'ational', 'ate', 0)
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OR self::replace($word, 'tional', 'tion', 0);
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break;
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case 'c':
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self::replace($word, 'enci', 'ence', 0)
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OR self::replace($word, 'anci', 'ance', 0);
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break;
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case 'e':
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self::replace($word, 'izer', 'ize', 0);
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break;
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case 'g':
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self::replace($word, 'logi', 'log', 0);
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break;
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case 'l':
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self::replace($word, 'entli', 'ent', 0)
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OR self::replace($word, 'ousli', 'ous', 0)
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OR self::replace($word, 'alli', 'al', 0)
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OR self::replace($word, 'bli', 'ble', 0)
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OR self::replace($word, 'eli', 'e', 0);
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break;
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case 'o':
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self::replace($word, 'ization', 'ize', 0)
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OR self::replace($word, 'ation', 'ate', 0)
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OR self::replace($word, 'ator', 'ate', 0);
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break;
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case 's':
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self::replace($word, 'iveness', 'ive', 0)
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OR self::replace($word, 'fulness', 'ful', 0)
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OR self::replace($word, 'ousness', 'ous', 0)
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OR self::replace($word, 'alism', 'al', 0);
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break;
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case 't':
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self::replace($word, 'biliti', 'ble', 0)
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OR self::replace($word, 'aliti', 'al', 0)
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OR self::replace($word, 'iviti', 'ive', 0);
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break;
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}
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return $word;
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}
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/**
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* Step 3
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*
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* @param string $word String to stem
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*/
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private static function step3($word)
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{
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switch (substr($word, -2, 1)) {
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case 'a':
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self::replace($word, 'ical', 'ic', 0);
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break;
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case 's':
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self::replace($word, 'ness', '', 0);
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break;
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case 't':
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self::replace($word, 'icate', 'ic', 0)
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OR self::replace($word, 'iciti', 'ic', 0);
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break;
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case 'u':
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self::replace($word, 'ful', '', 0);
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break;
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case 'v':
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self::replace($word, 'ative', '', 0);
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break;
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case 'z':
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self::replace($word, 'alize', 'al', 0);
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break;
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}
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return $word;
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}
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/**
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* Step 4
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*
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* @param string $word Word to stem
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*/
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private static function step4($word)
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{
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switch (substr($word, -2, 1)) {
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case 'a':
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self::replace($word, 'al', '', 1);
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break;
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case 'c':
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self::replace($word, 'ance', '', 1)
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OR self::replace($word, 'ence', '', 1);
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break;
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case 'e':
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self::replace($word, 'er', '', 1);
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break;
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case 'i':
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self::replace($word, 'ic', '', 1);
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break;
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case 'l':
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self::replace($word, 'able', '', 1)
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OR self::replace($word, 'ible', '', 1);
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break;
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case 'n':
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self::replace($word, 'ant', '', 1)
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OR self::replace($word, 'ement', '', 1)
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OR self::replace($word, 'ment', '', 1)
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OR self::replace($word, 'ent', '', 1);
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break;
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case 'o':
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if (substr($word, -4) == 'tion' OR substr($word, -4) == 'sion') {
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self::replace($word, 'ion', '', 1);
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} else {
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self::replace($word, 'ou', '', 1);
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}
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break;
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case 's':
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self::replace($word, 'ism', '', 1);
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break;
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case 't':
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self::replace($word, 'ate', '', 1)
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OR self::replace($word, 'iti', '', 1);
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break;
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case 'u':
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self::replace($word, 'ous', '', 1);
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break;
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case 'v':
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self::replace($word, 'ive', '', 1);
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break;
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case 'z':
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self::replace($word, 'ize', '', 1);
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break;
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}
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return $word;
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}
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/**
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* Step 5
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*
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* @param string $word Word to stem
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*/
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private static function step5($word)
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{
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// Part a
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if (substr($word, -1) == 'e') {
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if (self::m(substr($word, 0, -1)) > 1) {
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self::replace($word, 'e', '');
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} elseif (self::m(substr($word, 0, -1)) == 1) {
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if (!self::cvc(substr($word, 0, -1))) {
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self::replace($word, 'e', '');
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}
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}
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}
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// Part b
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if (self::m($word) > 1 AND self::doubleConsonant($word) AND substr($word, -1) == 'l') {
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$word = substr($word, 0, -1);
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}
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return $word;
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}
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/**
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* Replaces the first string with the second, at the end of the string. If third
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* arg is given, then the preceding string must match that m count at least.
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*
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* @param string $str String to check
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* @param string $check Ending to check for
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* @param string $repl Replacement string
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* @param int $m Optional minimum number of m() to meet
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* @return bool Whether the $check string was at the end
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* of the $str string. True does not necessarily mean
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* that it was replaced.
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*/
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private static function replace(&$str, $check, $repl, $m = null)
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{
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$len = 0 - strlen($check);
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if (substr($str, $len) == $check) {
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$substr = substr($str, 0, $len);
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if (is_null($m) OR self::m($substr) > $m) {
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$str = $substr . $repl;
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}
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return true;
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}
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return false;
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}
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/**
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* What, you mean it's not obvious from the name?
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*
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* m() measures the number of consonant sequences in $str. if c is
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* a consonant sequence and v a vowel sequence, and <..> indicates arbitrary
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* presence,
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*
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* <c><v> gives 0
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* <c>vc<v> gives 1
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* <c>vcvc<v> gives 2
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* <c>vcvcvc<v> gives 3
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*
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* @param string $str The string to return the m count for
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* @return int The m count
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*/
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private static function m($str)
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{
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$c = self::$regex_consonant;
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$v = self::$regex_vowel;
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$str = preg_replace("#^$c+#", '', $str);
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$str = preg_replace("#$v+$#", '', $str);
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preg_match_all("#($v+$c+)#", $str, $matches);
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return count($matches[1]);
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}
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/**
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* Returns true/false as to whether the given string contains two
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* of the same consonant next to each other at the end of the string.
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*
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* @param string $str String to check
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* @return bool Result
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*/
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private static function doubleConsonant($str)
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{
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$c = self::$regex_consonant;
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return preg_match("#" . $c . "{2}$#", $str, $matches) AND $matches[0][0] == $matches[0][1];
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}
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/**
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* Checks for ending CVC sequence where second C is not W, X or Y
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*
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* @param string $str String to check
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* @return bool Result
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*/
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private static function cvc($str)
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{
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$c = self::$regex_consonant;
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$v = self::$regex_vowel;
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return preg_match("#($c$v$c)$#", $str, $matches)
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AND strlen($matches[1]) == 3
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AND $matches[1][2] != 'w'
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AND $matches[1][2] != 'x'
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AND $matches[1][2] != 'y';
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}
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}
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?>
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