using System;
using System.IO;
namespace porter
{
/*
Porter stemmer in CSharp, based on the Java port. 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
*/
/**
* 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.
*/
class Stemmer
{
private char[] b;
private int i, /* offset into b */
i_end, /* offset to end of stemmed word */
j, k;
private static int INC = 50;
/* unit of size whereby b is increased */
public Stemmer()
{
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 override 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 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;
}
}
/* 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 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 bool 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 bool 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 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
k. */
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;
}
/* r(s) is used further down. */
private 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 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 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 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--;
}
/** 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 Stemmer. 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 Stemmer class.
* Usage: Stemmer file-name file-name ...
*/
public static void Main(String[] args)
{
if (args.Length == 0)
{
Console.WriteLine("Usage: Stemmer <input file>");
return;
}
char[] w = new char[501];
Stemmer s = new Stemmer();
for (int i = 0; i < args.Length; i++)
try
{
FileStream _in = new FileStream(args[i], FileMode.Open, FileAccess.Read);
try
{
while (true)
{
int ch = _in.ReadByte();
if (Char.IsLetter((char)ch))
{
int j = 0;
while (true)
{
ch = Char.ToLower((char)ch);
w[j] = (char)ch;
if (j < 500)
j++;
ch = _in.ReadByte();
if (!Char.IsLetter((char)ch))
{
/* to test add(char ch) */
for (int c = 0; c < j; C++)
s.add(w[c]);
/* 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()); */
Console.Write(u);
break;
}
}
}
if (ch < 0)
break;
Console.Write((char)ch);
}
}
catch (IOException)
{
Console.WriteLine("error reading " + args[i]);
break;
}
}
catch (FileNotFoundException)
{
Console.WriteLine("file " + args[i] + " not found");
break;
}
}
}
}
پاسخ با نقل قول
