/**************************************************************************
*
* stem_complex.c -- Stemming code
* Copyright (C) 1994 Linh Huynh (linh@kbs.citri.edu.au)
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*
* $Id: stem_complex.c,v 1.1 1997/09/02 09:17:25 wew Exp $
*
**************************************************************************/
#include <sys/types.h>
#include <stdio.h>
#include <string.h>
#include <ctype.h>
#include "stem_recode_rules.i"
#include "stem_context_rules.i"
#include "stem.h"
#define MIN_STEM_LENGTH 2
#define MAX_ENDING_SIZE 11
#define PREDEFINED_SIZE (MAX_ENDING_SIZE + MIN_STEM_LENGTH)
#define EOS '\0'
static char *remove_ending(char *word, int w_len);
static void recode_stem(char *stem_end);
void stem_complex(u_char *word);
/*
* Method 0 - Do not stem or case fold.
* Method 1 - Case fold.
* Method 2 - Stem.
* Method 3 - Case fold and stem.
*/
void stemmer(int method, u_char* word)
{
if (method & 1)
{
int len = *word;
char *w = (char*)word+1;
for(; len; len--, w++)
*w = tolower(*w);
}
if (method & 2)
stem_complex(word);
}
/* =========================================================================
* Function: stem
* Description:
* Implemetation of the Lovins' stemming algorithm described in
* J.B. Lovins, "Development of a Stemming Algorithm",
* Mechanical Translation and Computational Linguistics, Vol 11,1968.
* Input: a word string with the length in the first byte
* Output: the stemmed word
* ========================================================================= */
void
stem_complex(u_char *word)
{
char *word_start; /* points to first letter of word */
char *stem_end; /* points to last character of stem portion */
int old_length; /* length of word */
int new_length; /* length after stemming */
old_length = *word;
/* The word must be at least MIN_STEM_LENGTH characters mg_long. */
if (old_length <= MIN_STEM_LENGTH) return;
word_start = (char*)word + 1; /* jump over length byte */
word[old_length+1] = '\0'; /* null terminate string */
stem_end = remove_ending(word_start, old_length);
recode_stem(stem_end);
/* fix up new length */
/* have to use strlen because have no other way of telling length */
new_length = strlen(word_start);
*word = new_length;
}/*stem_complex*/
/* =========================================================================
*
* Data structure for recoding and the method for recoding the stem.
*
* ========================================================================= */
typedef struct
{
char *old_end; /* old ending */
char *new_end; /* new ending */
char old_offset; /* length of the old ending - 1 */
int (*cond)(); /* condition rule */
char end_group; /* signal the end of the group */
} Recode_Rules;
/*
Stem terminations are divided into groups having the same last
character
*/
static Recode_Rules Rules[] =
{
"uad", "uas", 2, NULL, 0,
"vad", "vas", 2, NULL, 0,
"cid", "cis", 2, NULL, 0,
"lid", "lis", 2, NULL, 0,
"erid", "eris", 3, NULL, 0,
"pand", "pans", 3, NULL, 0,
"end", "ens", 2, s, 0,
"end", "ens", 2, m, 0,
"ond", "ons", 2, NULL, 0,
"lud", "lus", 2, NULL, 0,
"rud", "rus", 2, NULL, 1,
"ul", "l", 1, aio, 1,
"istr", "ister", 3, NULL, 0,
"metr", "meter", 3, NULL, 0,
"her", "hes", 2, pt, 1,
"urs", "ur", 2, NULL, 1,
"uct", "uc", 2, NULL, 0,
"umpt", "um", 3, NULL, 0,
"rpt", "rb", 2, NULL, 0,
"mit", "mis", 2, NULL, 0,
"ert", "ers", 2, NULL, 0,
"et", "es", 1, n, 0,
"yt", "ys", 1, NULL, 1,
"iev", "ief", 2, NULL, 0,
"olv", "olut", 2, NULL, 1,
"bex", "bic", 2, NULL, 0,
"dex", "dic", 2, NULL, 0,
"pex", "pic", 2, NULL, 0,
"tex", "tic", 2, NULL, 0,
"ax", "ac", 1, NULL, 0,
"ex", "ec", 1, NULL, 0,
"ix", "ic", 1, NULL, 0,
"lux", "luc", 2, NULL, 1,
"yz", "ys", 1, NULL, 1
};
typedef struct last
{
char c; /* The last character */
struct last *left; /* used in balanced */
struct last *right; /* binary tree */
Recode_Rules *pt; /* location of approriate group */
} Last_Char_Node;
static Last_Char_Node pr[] =
{
'd', NULL, NULL, Rules,
'l', pr, pr+2, Rules+11,
'r', NULL, NULL, Rules+12,
's', pr+1, pr+6, Rules+15,
't', NULL, pr+5, Rules+16,
'v', NULL, NULL, Rules+23,
'x', pr+4, pr+7, Rules+25,
'z', NULL, NULL, Rules+33,
};
/*****************************************************************************
*
* Recode the stem according to the transformation rules.
*
*****************************************************************************/
static void
recode_stem(char *stem_end)
{
static Last_Char_Node *root = pr+3;
Last_Char_Node *p_last = root;
Recode_Rules *rule; /* points to the transformation list */
char *h, /* points to start of possible ending*/
ch, /* last character of the old ending */
ch2;
h = stem_end - 1;
ch = *stem_end;
if (*h == ch) /* Check for double consonant */
{
if (strchr("bdglmnprst", ch) != NULL)
{
*stem_end = EOS;
stem_end = h;
}
}
do /* Check for the last character */
{
ch2 = p_last->c;
if (ch == ch2)
break;
else if (ch > ch2)
p_last = p_last->right;
else
p_last = p_last->left;
} while (p_last != NULL);
if (p_last != NULL) /* Check for the rest of suffix list */
{
rule = p_last->pt;
for(;;)
{
h = stem_end - rule->old_offset;
if (strcmp(h,rule->old_end) == 0)
{
if (!rule->cond || (*rule->cond)(*(h-1)))
{
(void)strcpy(h,rule->new_end);
break;
}
}
if (rule->end_group) break;
rule++;
}
}
}
/* ======================================================================
*
* List of endings and the method to remove the ending
*
* ======================================================================*/
/************ Data structures for list of endings ********************/
typedef struct
{
char *ending; /* old ending */
int (*cond)(); /* conditional rule */
signed char left_offset; /* used to find the siblings */
signed char right_offset; /* in balanced binary tree */
} Ending_List;
/*
The original list of endings is re-organised into groups having
the same length and the same first character.
*/
static Ending_List List[] =
{
"a", NULL, 0, 0,
"ae", NULL, 0, 0,
"al", BB, -1, 2,
"ar", X, 0, 0,
"as", B, -1, 0,
"acy", NULL, 0, 1,
"age", B, 0, 0,
"aic", NULL, -2, 1,
"als", BB, 0, 0,
"ant", B, -2, 2,
"ars", O, 0, 0,
"ary", F, -1, 2,
"ata", NULL, 0, 0,
"ate", NULL, -1, 0,
"able", NULL, 0, 1,
"ably", NULL, 0, 0,
"ages", B, -2, 2,
"ally", B, 0, 0,
"ance", B, -1, 1,
"ancy", B, 0, 0,
"ants", B, -4, 4,
"aric", NULL, 0, 0,
"arly", K, -1, 1,
"ated", I, 0, 0,
"ates", NULL, -2, 2,
"atic", B, 0, 0,
"ator", NULL, -1, 0,
"acies", NULL, 0, 0,
"acity", NULL, -1, 1,
"aging", B, 0, 0,
"aical", NULL, -2, 2,
"alist", NULL, 0, 0,
"alism", B, -1, 0,
"ality", NULL, -3, 3,
"alize", NULL, 0, 1,
"allic", BB, 0, 0,
"anced", B, -2, 2,
"ances", B, 0, 0,
"antic", C, -1, 0,
"arial", NULL, -6, 6,
"aries", NULL, 0, 1,
"arily", NULL, 0, 0,
"arity", B, -2, 2,
"arize", NULL, 0, 0,
"aroid", NULL, -1, 0,
"ately", NULL, -3, 3,
"ating", I, 0, 1,
"ation", B, 0, 0,
"ative", NULL, -2, 2,
"ators", NULL, 0, 0,
"atory", NULL, -1, 1,
"ature", E, 0, 0,
"aceous", NULL, 0, 1,
"acious", B, 0, 0,
"action", G, -2, 2,
"alness", NULL, 0, 0,
"ancial", NULL, -1, 1,
"ancies", NULL, 0, 0,
"ancing", B, -4, 4,
"ariser", NULL, 0, 0,
"arized", NULL, -1, 1,
"arizer", NULL, 0, 0,
"atable", NULL, -2, 2,
"ations", B, 0, 0,
"atives", NULL, -1, 0,
"ability", NULL, 0, 1,
"aically", NULL, 0, 0,
"alistic", B, -2, 2,
"alities", NULL, 0, 0,
"ariness", E, -1, 0,
"aristic", NULL, -3, 3,
"arizing", NULL, 0, 1,
"ateness", NULL, 0, 0,
"atingly", NULL, -2, 2,
"ational", B, 0, 0,
"atively", NULL, -1, 1,
"ativism", NULL, 0, 0,
"ableness", NULL, 0, 1,
"arizable", NULL, 0, 0,
"allically", C, 0, 0,
"antaneous", NULL, -1, 1,
"antiality", NULL, 0, 0,
"arisation", NULL, -2, 2,
"arization", NULL, 0, 0,
"ationally", B, -1, 1,
"ativeness", NULL, 0, 0,
"antialness", NULL, 0, 0,
"arisations", NULL, -1, 1,
"arizations", NULL, 0, 0,
"alistically", B, 0, 1,
"arizability", NULL, 0, 0,
"e", NULL, 0, 0,
"ed", E, 0, 0,
"en", F, -1, 1,
"es", E, 0, 0,
"eal", Y, 0, 0,
"ear", Y, -1, 1,
"ely", E, 0, 0,
"ene", E, -2, 2,
"ent", C, 0, 0,
"ery", E, -1, 1,
"ese", NULL, 0, 0,
"ealy", Y, 0, 1,
"edly", E, 0, 0,
"eful", NULL, -2, 1,
"eity", NULL, 0, 0,
"ence", NULL, -2, 2,
"ency", NULL, 0, 0,
"ened", E, -1, 2,
"enly", E, 0, 0,
"eous", NULL, -1, 0,
"early", Y, 0, 1,
"ehood", NULL, 0, 0,
"eless", NULL, -2, 2,
"elity", NULL, 0, 0,
"ement", NULL, -1, 0,
"enced", NULL, -3, 3,
"ences", NULL, 0, 1,
"eness", E, 0, 0,
"ening", E, -2, 2,
"ental", NULL, 0, 0,
"ented", C, -1, 1,
"ently", NULL, 0, 0,
"eature", Z, 0, 0,
"efully", NULL, -1, 1,
"encies", NULL, 0, 0,
"encing", NULL, -2, 2,
"ential", NULL, 0, 0,
"enting", C, -1, 1,
"entist", NULL, 0, 1,
"eously", NULL, 0, 0,
"elihood", E, 0, 1,
"encible", NULL, 0, 0,
"entally", NULL, -2, 2,
"entials", NULL, 0, 0,
"entiate", NULL, -1, 1,
"entness", NULL, 0, 0,
"entation", NULL, 0, 0,
"entially", NULL, -1, 1,
"eousness", NULL, 0, 0,
"eableness", E, 0, 1,
"entations", NULL, 0, 0,
"entiality", NULL, -2, 2,
"entialize", NULL, 0, 0,
"entiation", NULL, -1, 0,
"entialness", NULL, 0, 0,
"ful", NULL, 0, 0,
"fully", NULL, 0, 0,
"fulness", NULL, 0, 0,
"hood", NULL, 0, 0,
"i", NULL, 0, 0,
"ia", NULL, 0, 0,
"ic", NULL, -1, 1,
"is", NULL, 0, 0,
"ial", NULL, 0, 0,
"ian", NULL, -1, 1,
"ics", NULL, 0, 1,
"ide", L, 0, 0,
"ied", NULL, -3, 3,
"ier", NULL, 0, 0,
"ies", P, -1, 0,
"ily", NULL, -1, 1,
"ine", M, 0, 0,
"ing", N, -5, 5,
"ion", Q, 0, 0,
"ish", C, -1, 1,
"ism", B, 0, 1,
"ist", NULL, 0, 0,
"ite", AA, -3, 3,
"ity", NULL, 0, 0,
"ium", NULL, -1, 0,
"ive", NULL, -1, 1,
"ize", F, 0, 0,
"ials", NULL, 0, 0,
"ians", NULL, -1, 0,
"ible", NULL, -1, 1,
"ibly", NULL, 0, 0,
"ical", NULL, -2, 2,
"ides", L, 0, 0,
"iers", NULL, -1, 1,
"iful", NULL, 0, 0,
"ines", M, -4, 4,
"ings", N, 0, 0,
"ions", B, -1, 1,
"ious", NULL, 0, 0,
"isms", B, -2, 2,
"ists", NULL, 0, 0,
"itic", H, -1, 1,
"ized", F, 0, 1,
"izer", F, 0, 0,
"ially", NULL, 0, 0,
"icant", NULL, -1, 1,
"ician", NULL, 0, 0,
"icide", NULL, -2, 2,
"icism", NULL, 0, 0,
"icist", NULL, -1, 0,
"icity", NULL, -3, 3,
"idine", I, 0, 1,
"iedly", NULL, 0, 0,
"ihood", NULL, -2, 2,
"inate", NULL, 0, 0,
"iness", NULL, -1, 0,
"ingly", B, -6, 6,
"inism", J, 0, 1,
"inity", CC, 0, 0,
"ional", NULL, -2, 2,
"ioned", NULL, 0, 0,
"ished", NULL, -1, 0,
"istic", NULL, -3, 3,
"ities", NULL, 0, 1,
"itous", NULL, 0, 0,
"ively", NULL, -2, 2,
"ivity", NULL, 0, 0,
"izers", F, -1, 1,
"izing", F, 0, 0,
"ialist", NULL, 0, 0,
"iality", NULL, -1, 1,
"ialize", NULL, 0, 0,
"ically", NULL, -2, 2,
"icance", NULL, 0, 0,
"icians", NULL, -1, 1,
"icists", NULL, 0, 0,
"ifully", NULL, -4, 4,
"ionals", NULL, 0, 0,
"ionate", D, -1, 1,
"ioning", NULL, 0, 0,
"ionist", NULL, -2, 2,
"iously", NULL, 0, 0,
"istics", NULL, -1, 1,
"izable", E, 0, 0,
"ibility", NULL, 0, 0,
"icalism", NULL, -1, 1,
"icalist", NULL, 0, 1,
"icality", NULL, 0, 0,
"icalize", NULL, -3, 3,
"ication", G, 0, 0,
"icianry", NULL, -1, 0,
"ination", NULL, -1, 1,
"ingness", NULL, 0, 0,
"ionally", NULL, -5, 5,
"isation", NULL, 0, 0,
"ishness", NULL, -1, 1,
"istical", NULL, 0, 1,
"iteness", NULL, 0, 0,
"iveness", NULL, -3, 3,
"ivistic", NULL, 0, 0,
"ivities", NULL, -1, 0,
"ization", F, -1, 1,
"izement", NULL, 0, 0,
"ibleness", NULL, 0, 0,
"icalness", NULL, -1, 1,
"ionalism", NULL, 0, 0,
"ionality", NULL, -2, 2,
"ionalize", NULL, 0, 0,
"iousness", NULL, -1, 1,
"izations", NULL, 0, 0,
"ionalness", NULL, 0, 1,
"istically", NULL, 0, 0,
"itousness", NULL, -2, 2,
"izability", NULL, 0, 0,
"izational", NULL, -1, 0,
"izationally", B, 0, 0,
"ly", B, 0, 0,
"less", NULL, 0, 1,
"lily", NULL, 0, 0,
"lessly", NULL, 0, 0,
"lessness", NULL, 0, 0,
"ness", NULL, 0, 0,
"nesses", NULL, 0, 0,
"o", NULL, 0, 0,
"on", S, 0, 1,
"or", T, 0, 0,
"oid", NULL, 0, 0,
"one", R, -1, 1,
"ous", NULL, 0, 0,
"ogen", NULL, 0, 0,
"oidal", NULL, 0, 0,
"oides", NULL, -1, 2,
"otide", NULL, 0, 0,
"ously", NULL, -1, 0,
"oidism", NULL, 0, 0,
"oidally", NULL, 0, 1,
"ousness", NULL, 0, 0,
"s", W, 0, 0,
"s'", NULL, 0, 0,
"um", U, 0, 1,
"us", V, 0, 0,
"ward", NULL, 0, 1,
"wise", NULL, 0, 0,
"y", B, 0, 0,
"yl", R, 0, 0,
"ying", B, 0, 1,
"yish", NULL, 0, 0,
"'s", NULL, 0, 0,
};
typedef struct node
{
char c; /* First character */
struct node *left; /* used in balanced */
struct node *right; /* binary tree */
Ending_List *ptr[11]; /* the approriate location */
} First_Char_Node;
static First_Char_Node First[] =
{
'\'', NULL, NULL, {NULL,
List+293, NULL, NULL, NULL, NULL,
NULL, NULL, NULL, NULL, NULL},
'a', First, NULL, {List,
List+2, List+9, List+20, List+39, List+58,
List+70, List+77, List+82, List+87, List+89},
'e', First+1, First+4, {List+91,
List+93, List+98, List+106, List+116, List+126,
List+133, List+138, List+142, List+145, NULL},
'f', NULL, NULL, {NULL,
NULL, List+146, NULL, List+147, NULL,
List+148, NULL, NULL, NULL, NULL},
'h', First+3, First+5, {NULL,
NULL, NULL, List+149, NULL, NULL,
NULL, NULL, NULL, NULL, NULL},
'i', NULL, NULL, {List+150,
List+152, List+163, List+181, List+202, List+222,
List+239, List+252, List+258, NULL, List+261},
'l', First+2, First+10, {NULL,
List+262, NULL, List+263, NULL, List+265,
NULL, List+266, NULL, NULL, NULL},
'n', NULL, NULL, {NULL,
NULL, NULL, List+267, NULL, List+268,
NULL, NULL, NULL, NULL, NULL},
'o', First+7, First+9, {List+269,
List+270, List+273, List+275, List+277, List+280,
List+281, NULL, NULL, NULL, NULL},
's', NULL, NULL, {List+283,
List+284, NULL, NULL, NULL, NULL,
NULL, NULL, NULL, NULL, NULL},
'u', First+8, First+12, {NULL,
List+285, NULL, NULL, NULL, NULL,
NULL, NULL, NULL, NULL, NULL},
'w', NULL, NULL, {NULL,
NULL, NULL, List+287, NULL, NULL,
NULL, NULL, NULL, NULL, NULL},
'y', First+11, NULL, {List+289,
List+290, NULL, List+291, NULL, NULL,
NULL, NULL, NULL, NULL, NULL},
};
/******************************************************************************
*
* Look for a match in the suffix list.
* Return the pointer to the end of the new stem if there is a match.
* Otherwise, return the pointer to the end of the original word.
*
* Method:
* * Search for the first character in the suffix list.
* * If there is match, search for the rest of the suffix list.
*
*****************************************************************************/
static char *
remove_ending(char *word, int w_len)
{
static First_Char_Node *root = First+6; /* the root of binary tree is 'l' */
First_Char_Node *p_first; /* Points to the first character */
/* of the possible suffix */
Ending_List *p_list; /* Points to the List of Endings */
char *suffix_start, /* Points to start of possible suffix */
*stem_end, /* Points to the end of possible stem */
ch1, ch2;
int s_len, /* Possible stem length */
e_offset, /* Offset from the end to the start of*/
/* possible suffix */
not_done = 1, cmp;
stem_end = word + w_len - 1;
if (w_len > PREDEFINED_SIZE) /* find the start of suffix */
suffix_start = word + w_len - MAX_ENDING_SIZE;
else
suffix_start = word + MIN_STEM_LENGTH;
ch1 = *suffix_start;
do /* Search for the first character */
{
p_first = root;
do
{
ch2 = p_first->c;
if (ch1 == ch2)
break;
else if (ch1 > ch2)
p_first = p_first->right;
else
p_first = p_first->left;
} while (p_first != NULL);
if (p_first != NULL) /* Search for the rest */
{
e_offset = stem_end - suffix_start;
if ((p_list = p_first->ptr[e_offset]) != NULL)
{
for(;;) /* no need to compare the first char */
{
cmp = strcmp(suffix_start+1, p_list->ending+1);
if (cmp > 0)
if (p_list->right_offset)
p_list += p_list->right_offset;
else
break;
else if (cmp < 0)
if (p_list->left_offset)
p_list += p_list->left_offset;
else
break;
else
{
s_len = suffix_start - word;
if (!p_list->cond ||
(*p_list->cond)(s_len,suffix_start-1))
{
*suffix_start = EOS;
stem_end = suffix_start - 1;
not_done = 0;
}
break;
}
}
}
}
suffix_start++;
} while (not_done && ((ch1 = *suffix_start) != EOS));
return (stem_end);
}
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