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/*
* Suffix stripping
* Martin Porter Stemming algorithm Finite state tranducer,
* Copyright (c) by Martin Porter
*/
using System;
using System.Runtime.InteropServices;
namespace ServiceRanking
{
/// <summary>
/// Summary description for PorterStemmer.
/// Thanks Martin
/// </summary>
public interface StemmerInterface
{
string stemTerm( string s );
}
[ClassInterface( ClassInterfaceType.None )]
public class PorterStemmer : StemmerInterface
{
private char[] _b;
private int i, // offset into b
i_end, // offset to end of stemmed word
j, k;
private static int INC = 200;
// unit of size whereby b is increased
public PorterStemmer()
{
_b = new char[INC];
i = 0;
i_end = 0;
}
public string stemTerm( string s )
{
setTerm( s );
stem();
return getTerm();
}
void setTerm( string s)
{
i = s.Length;
char[] new_b = new char[i];
for (int c = 0; c < i; c++)
new_b[c] = s[c];
_b = new_b;
}
public string getTerm()
{
return new String(_b, 0, i_end);
}
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;
}
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];
}
public override string ToString()
{
return new String(_b,0,i_end);
}
public int getResultLength()
{
return i_end;
}
public char[] getResultBuffer()
{
return _b;
}
private bool 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;
}
}
private 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++;
}
}
private bool vowelinstem()
{
int i;
for (i = 0; i <= j; i++)
if (! cons(i))
return true;
return false;
}
private bool doublec(int j)
{
if (j < 1)
return false;
if (_b[j] != _b[j-1])
return false;
return cons(j);
}
private bool 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 bool ends(String s)
{
int l = s.Length;
int o = k-l+1;
if (o < 0)
return false;
char[] sc = s.ToCharArray();
for (int i = 0; i < l; i++)
if (_b[o+i] != sc[i])
return false;
j = k-l;
return true;
}
/// setto(s) sets (j+1),...k to the characters in the string s, readjusting
//
private void setto(String s)
{
int l = s.Length;
int o = j+1;
char[] sc = s.ToCharArray();
for (int i = 0; i < l; i++)
_b[o+i] = sc[i];
k = j+l;
}
private void r(String s)
{
if (m() > 0)
setto(s);
}
private 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");
}
}
private void step2()
{
if (ends("y") && vowelinstem())
_b[k] = 'i';
}
private 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; }
break;
default :
break;
}
}
// step4() deals with -ic-, -full, -ness etc. similar strategy to step3.
private 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 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 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--;
}
public void stem()
{
k = i - 1;
if (k > 1)
{
step1();
step2();
step3();
step4();
step5();
step6();
}
i_end = k+1;
i = 0;
}
}
}
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I'm still alive...but temporarily moved to work on mobile & web stuffs(j2me/brew/php/flash...something not M$). things have just been very busy, and probably will continue...so don't have chance to maintain & respond. Hope will have time to try to write again, because many ideas with WPF &silver light are waiting. wish me luck
FYI:
- MESHSimPack project(c# library for measuring similarity among concepts of the MESH ontology):
http://sourceforge.net/projects/meshsimpack.
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