package ecologylab.generic;
/*
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
Modification
This version is derived from Release 4, modified by Jin Wang to use
StringBuffer instead of char array.
*/
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
/**
* 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.
*
* New version of PorterStemmer implemented with StringBuffer.
*/
public class NewPorterStemmer
extends Debug
{
//private char[] b;
private StringBuffer b;
private int i, /* offset into b */
i_end, /* offset to end of stemmed word */
j, k;
private boolean dirty = false;
private static final int INC = 256;
/* unit of size whereby b is increased */
public NewPorterStemmer()
{
b = new StringBuffer(INC);
i = 0;
i_end = 0;
}
/**
* reset() resets the stemmer so it can stem another word. If you invoke
* the stemmer by calling add(char) and then stem(), you must call reset()
* before starting another word.
*/
public void reset()
{
i = 0;
dirty = false;
}
/**
* 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())
b.setLength(i+INC);
b.setCharAt(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())
b.setLength(i+wLen+INC);
for (int c = 0; c < wLen; c++)
b.setCharAt(i++, w[c]);
}
public void add(String s)
{
reset();
int wLen = s.length();
b.setLength(wLen);
for (int c = 0; c < wLen; c++)
b.setCharAt(i++, s.charAt(c));
}
/*
public void add(String s)
{
add(s.toCharArray(), s.length());
}
*/
/**
* 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.)
*/
@Override
public String toString()
{
// force ArrayCopy here, otherwise StringBuffer gets shared and SLOW
return b.substring(0, i_end);
// return new String(b,0,i_end);
}
public String stem(String s)
{
/*
NewPorterStemmer stemmer = new NewPorterStemmer();
stemmer.add(s);
stemmer.stem();
return stemmer.toString();
*/
add(s);
stem();
return toString();
}
/**
* 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 StringBuffer getResultBuffer() { return b; }
/* cons(i) is true <=> b[i] is a consonant. */
private final boolean cons(int i)
{
switch (b.charAt(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.charAt(j) != b.charAt(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.charAt(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;
int oTracker = o;
int bLength = b.length();
for (int i = 0; i < l; i++)
{
if (oTracker++ >= bLength)
return false;
if (b.charAt(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.setCharAt(o+i, s.charAt(i));
k = j+l;
dirty = true;
}
/* 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.charAt(k) == 's')
{ if (ends("sses")) k -= 2; else
if (ends("ies")) setto("i"); else
if (b.charAt(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.charAt(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.setCharAt(k,'i');
dirty = true;
}
/* 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.charAt(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.charAt(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.charAt(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.charAt(j) == 's' || b.charAt(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.charAt(k) == 'e')
{ int a = m();
if (a > 1 || a == 1 && !cvc(k-1))
k--;
}
if (b.charAt(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;
}
/** Test program for demonstrating the PorterStemmer. It reads text from a
* a list of files, stems each word, and writes the result to standard
* output. Note that the word stemmed is expected to be in lower case:
* forcing lower case must be done outside the PorterStemmer class.
* Usage: PorterStemmer file-name file-name ...
*/
public static void main(String[] args)
{
char[] w = new char[501];
NewPorterStemmer s = new NewPorterStemmer();
//String test = "computers";
//System.out.println("testString is " + s.stem(test));
for (int i = 0; i < args.length; i++)
try
{
FileInputStream in = new FileInputStream(args[i]);
try
{ while(true)
{ int ch = in.read();
if (Character.isLetter((char) ch))
{
int j = 0;
while(true)
{ ch = Character.toLowerCase((char) ch);
w[j] = (char) ch;
if (j < 500) j++;
ch = in.read();
if (!Character.isLetter((char) ch))
{
/* to test add(char ch) */
for (int c = 0; c < j; c++)
s.add(w[c]);
//System.out.println(s.toString());
/* or, to test add(char[] w, int j) */
//s.add(w, j);
s.stem();
{ String u;
/* and now, to test toString() : */
u = s.toString();
/* to test getResultBuffer(), getResultLength() : */
/* u = new String(s.getResultBuffer(), 0, s.getResultLength()); */
System.out.print(u);
}
break;
}
}
}
if (ch < 0) break;
System.out.print((char)ch);
}
}
catch (IOException e)
{ System.out.println("error reading " + args[i]);
break;
}
}
catch (FileNotFoundException e)
{ System.out.println("file " + args[i] + " not found");
break;
}
}
}