| /* |
| * Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. |
| * The ASF licenses this file to You under the Apache License, Version 2.0 |
| * (the "License"); you may not use this file except in compliance with |
| * the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| package opennlp.summarization.preprocess; |
| |
| /* |
| |
| Porter stemmer in Java. The original paper is in |
| |
| Porter, 1980, An algorithm for suffix stripping, Program, Vol. 14, |
| no. 3, pp 130-137, |
| |
| See also http://www.tartarus.org/~martin/PorterStemmer |
| |
| History: |
| |
| Release 1 |
| |
| Bug 1 (reported by Gonzalo Parra 16/10/99) fixed as marked below. |
| The words 'aed', 'eed', 'oed' leave k at 'a' for step 3, and b[k-1] |
| is then out outside the bounds of b. |
| |
| Release 2 |
| |
| Similarly, |
| |
| Bug 2 (reported by Steve Dyrdahl 22/2/00) fixed as marked below. |
| 'ion' by itself leaves j = -1 in the test for 'ion' in step 5, and |
| b[j] is then outside the bounds of b. |
| |
| Release 3 |
| |
| Considerably revised 4/9/00 in the light of many helpful suggestions |
| from Brian Goetz of Quiotix Corporation (brian@quiotix.com). |
| |
| Release 4 |
| |
| */ |
| |
| import java.io.*; |
| |
| import opennlp.tools.stemmer.Stemmer; |
| |
| /** |
| * Stemmer, implementing the Porter Stemming Algorithm |
| * |
| * The Stemmer class transforms a word into its root form. The input |
| * word can be provided a character at time (by calling add()), or at once |
| * by calling one of the various stem(something) methods. |
| */ |
| |
| public class PorterStemmer implements Stemmer |
| { private char[] b; |
| private int i, /* offset into b */ |
| i_end, /* offset to end of stemmed word */ |
| j, k; |
| private static final int INC = 50; |
| /* unit of size whereby b is increased */ |
| public PorterStemmer() |
| { b = new char[INC]; |
| i = 0; |
| i_end = 0; |
| } |
| |
| /** |
| * Add a character to the word being stemmed. When you are finished |
| * adding characters, you can call stem(void) to stem the word. |
| */ |
| |
| public void add(char ch) |
| { if (i == b.length) |
| { char[] new_b = new char[i+INC]; |
| for (int c = 0; c < i; c++) new_b[c] = b[c]; |
| b = new_b; |
| } |
| b[i++] = ch; |
| } |
| |
| |
| /** Adds wLen characters to the word being stemmed contained in a portion |
| * of a char[] array. This is like repeated calls of add(char ch), but |
| * faster. |
| */ |
| |
| public void add(char[] w, int wLen) |
| { if (i+wLen >= b.length) |
| { char[] new_b = new char[i+wLen+INC]; |
| for (int c = 0; c < i; c++) new_b[c] = b[c]; |
| b = new_b; |
| } |
| for (int c = 0; c < wLen; c++) b[i++] = w[c]; |
| } |
| |
| /** |
| * After a word has been stemmed, it can be retrieved by toString(), |
| * or a reference to the internal buffer can be retrieved by getResultBuffer |
| * and getResultLength (which is generally more efficient.) |
| */ |
| public String toString() { return new String(b,0,i_end); } |
| |
| /** |
| * Returns the length of the word resulting from the stemming process. |
| */ |
| public int getResultLength() { return i_end; } |
| |
| /** |
| * Returns a reference to a character buffer containing the results of |
| * the stemming process. You also need to consult getResultLength() |
| * to determine the length of the result. |
| */ |
| public char[] getResultBuffer() { return b; } |
| |
| /* cons(i) is true <=> b[i] is a consonant. */ |
| |
| private final boolean cons(int i) |
| { switch (b[i]) |
| { case 'a': case 'e': case 'i': case 'o': case 'u': return false; |
| case 'y': return (i==0) ? true : !cons(i-1); |
| default: return true; |
| } |
| } |
| |
| /* m() measures the number of consonant sequences between 0 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 |
| .... |
| */ |
| |
| private final int m() |
| { int n = 0; |
| int i = 0; |
| while(true) |
| { if (i > j) return n; |
| if (! cons(i)) break; i++; |
| } |
| i++; |
| while(true) |
| { while(true) |
| { if (i > j) return n; |
| if (cons(i)) break; |
| i++; |
| } |
| i++; |
| n++; |
| while(true) |
| { if (i > j) return n; |
| if (! cons(i)) break; |
| i++; |
| } |
| i++; |
| } |
| } |
| |
| /* vowelinstem() is true <=> 0,...j contains a vowel */ |
| |
| private final boolean vowelinstem() |
| { int i; for (i = 0; i <= j; i++) if (! cons(i)) return true; |
| return false; |
| } |
| |
| /* doublec(j) is true <=> j,(j-1) contain a double consonant. */ |
| |
| private final boolean doublec(int j) |
| { if (j < 1) return false; |
| if (b[j] != b[j-1]) return false; |
| return cons(j); |
| } |
| |
| /* cvc(i) is true <=> i-2,i-1,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. |
| |
| */ |
| |
| private final boolean cvc(int i) |
| { if (i < 2 || !cons(i) || cons(i-1) || !cons(i-2)) return false; |
| { int ch = b[i]; |
| if (ch == 'w' || ch == 'x' || ch == 'y') return false; |
| } |
| return true; |
| } |
| |
| private final boolean ends(String s) |
| { int l = s.length(); |
| int o = k-l+1; |
| if (o < 0) return false; |
| for (int i = 0; i < l; i++) if (b[o+i] != s.charAt(i)) return false; |
| j = k-l; |
| return true; |
| } |
| |
| /* setto(s) sets (j+1),...k to the characters in the string s, readjusting |
| k. */ |
| |
| private final void setto(String s) |
| { int l = s.length(); |
| int o = j+1; |
| for (int i = 0; i < l; i++) b[o+i] = s.charAt(i); |
| k = j+l; |
| } |
| |
| /* r(s) is used further down. */ |
| |
| private final void r(String s) { if (m() > 0) setto(s); } |
| |
| /* step1() gets rid of plurals and -ed or -ing. e.g. |
| |
| caresses -> caress |
| ponies -> poni |
| ties -> ti |
| caress -> caress |
| cats -> cat |
| |
| feed -> feed |
| agreed -> agree |
| disabled -> disable |
| |
| matting -> mat |
| mating -> mate |
| meeting -> meet |
| milling -> mill |
| messing -> mess |
| |
| meetings -> meet |
| |
| */ |
| |
| private final void step1() |
| { if (b[k] == 's') |
| { if (ends("sses")) k -= 2; else |
| if (ends("ies")) setto("i"); else |
| if (b[k-1] != 's') k--; |
| } |
| if (ends("eed")) { if (m() > 0) k--; } else |
| if ((ends("ed") || ends("ing")) && vowelinstem()) |
| { k = j; |
| if (ends("at")) setto("ate"); else |
| if (ends("bl")) setto("ble"); else |
| if (ends("iz")) setto("ize"); else |
| if (doublec(k)) |
| { k--; |
| { int ch = b[k]; |
| if (ch == 'l' || ch == 's' || ch == 'z') k++; |
| } |
| } |
| else if (m() == 1 && cvc(k)) setto("e"); |
| } |
| } |
| |
| /* step2() turns terminal y to i when there is another vowel in the stem. */ |
| |
| private final void step2() { if (ends("y") && vowelinstem()) b[k] = 'i'; } |
| |
| /* step3() 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. */ |
| |
| private final void step3() { if (k == 0) return; /* For Bug 1 */ switch (b[k-1]) |
| { |
| case 'a': if (ends("ational")) { r("ate"); break; } |
| if (ends("tional")) { r("tion"); break; } |
| break; |
| case 'c': if (ends("enci")) { r("ence"); break; } |
| if (ends("anci")) { r("ance"); break; } |
| break; |
| case 'e': if (ends("izer")) { r("ize"); break; } |
| break; |
| case 'l': if (ends("bli")) { r("ble"); break; } |
| if (ends("alli")) { r("al"); break; } |
| if (ends("entli")) { r("ent"); break; } |
| if (ends("eli")) { r("e"); break; } |
| if (ends("ousli")) { r("ous"); break; } |
| break; |
| case 'o': if (ends("ization")) { r("ize"); break; } |
| if (ends("ation")) { r("ate"); break; } |
| if (ends("ator")) { r("ate"); break; } |
| break; |
| case 's': if (ends("alism")) { r("al"); break; } |
| if (ends("iveness")) { r("ive"); break; } |
| if (ends("fulness")) { r("ful"); break; } |
| if (ends("ousness")) { r("ous"); break; } |
| break; |
| case 't': if (ends("aliti")) { r("al"); break; } |
| if (ends("iviti")) { r("ive"); break; } |
| if (ends("biliti")) { r("ble"); break; } |
| break; |
| case 'g': if (ends("logi")) { r("log"); break; } |
| } } |
| |
| /* step4() deals with -ic-, -full, -ness etc. similar strategy to step3. */ |
| |
| private final void step4() { switch (b[k]) |
| { |
| case 'e': if (ends("icate")) { r("ic"); break; } |
| if (ends("ative")) { r(""); break; } |
| if (ends("alize")) { r("al"); break; } |
| break; |
| case 'i': if (ends("iciti")) { r("ic"); break; } |
| break; |
| case 'l': if (ends("ical")) { r("ic"); break; } |
| if (ends("ful")) { r(""); break; } |
| break; |
| case 's': if (ends("ness")) { r(""); break; } |
| break; |
| } } |
| |
| /* step5() takes off -ant, -ence etc., in context <c>vcvc<v>. */ |
| |
| private final void step5() |
| { if (k == 0) return; /* for Bug 1 */ switch (b[k-1]) |
| { case 'a': if (ends("al")) break; return; |
| case 'c': if (ends("ance")) break; |
| if (ends("ence")) break; return; |
| case 'e': if (ends("er")) break; return; |
| case 'i': if (ends("ic")) break; return; |
| case 'l': if (ends("able")) break; |
| if (ends("ible")) break; return; |
| case 'n': if (ends("ant")) break; |
| if (ends("ement")) break; |
| if (ends("ment")) break; |
| /* element etc. not stripped before the m */ |
| if (ends("ent")) break; return; |
| case 'o': if (ends("ion") && j >= 0 && (b[j] == 's' || b[j] == 't')) break; |
| /* j >= 0 fixes Bug 2 */ |
| if (ends("ou")) break; return; |
| /* takes care of -ous */ |
| case 's': if (ends("ism")) break; return; |
| case 't': if (ends("ate")) break; |
| if (ends("iti")) break; return; |
| case 'u': if (ends("ous")) break; return; |
| case 'v': if (ends("ive")) break; return; |
| case 'z': if (ends("ize")) break; return; |
| default: return; |
| } |
| if (m() > 1) k = j; |
| } |
| |
| /* step6() removes a final -e if m() > 1. */ |
| |
| private final void step6() |
| { j = k; |
| if (b[k] == 'e') |
| { int a = m(); |
| if (a > 1 || a == 1 && !cvc(k-1)) k--; |
| } |
| if (b[k] == 'l' && doublec(k) && m() > 1) k--; |
| } |
| |
| /** Stem the word placed into the Stemmer buffer through calls to add(). |
| * Returns true if the stemming process resulted in a word different |
| * from the input. You can retrieve the result with |
| * getResultLength()/getResultBuffer() or toString(). |
| */ |
| public void stem() |
| { k = i - 1; |
| if (k > 1) { step1(); step2(); step3(); step4(); step5(); step6(); } |
| i_end = k+1; i = 0; |
| } |
| |
| public CharSequence stem(CharSequence word) |
| { |
| b = new char[word.length()]; |
| char[] arr = word.toString().toCharArray(); |
| for(k=0;k<arr.length;k++) this.add(arr[k]); |
| stem(); |
| return this.toString(); |
| } |
| } |
| |
