mirror of
https://github.com/lxsang/antd-lua-plugin
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704 lines
13 KiB
C
704 lines
13 KiB
C
/* This is the Porter stemming algorithm, coded up in ANSI C by the
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* author. It may be be regarded as canonical, in that it follows the
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* algorithm presented in
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*
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* Porter, 1980, An algorithm for suffix stripping, Program, Vol. 14,
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* no. 3, pp 130-137,
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*
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* only differing from it at the points marked --DEPARTURE-- below.
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*
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* See also http://www.tartarus.org/~martin/PorterStemmer
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*
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* The algorithm as described in the paper could be exactly replicated
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* by adjusting the points of DEPARTURE, but this is barely necessary,
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* because (a) the points of DEPARTURE are definitely improvements, and
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* (b) no encoding of the Porter stemmer I have seen is anything like
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* as exact as this version, even with the points of DEPARTURE!
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*
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* You can compile it on Unix with 'gcc -O3 -o stem stem.c' after which
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* 'stem' takes a list of inputs and sends the stemmed equivalent to
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* stdout.
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*
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* The algorithm as encoded here is particularly fast.
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*
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* Release 1: was many years ago
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* Release 2: 11 Apr 2013
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* fixes a bug noted by Matt Patenaude <matt@mattpatenaude.com>,
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*
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* case 'o': if (ends("\03" "ion") && (b[j] == 's' || b[j] == 't')) break;
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* ==>
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* case 'o': if (ends("\03" "ion") && j >= k0 && (b[j] == 's' || b[j] == 't')) break;
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*
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* to avoid accessing b[k0-1] when the word in b is "ion".
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* Release 3: 25 Mar 2014
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* fixes a similar bug noted by Klemens Baum <klemensbaum@gmail.com>,
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* that if step1ab leaves a one letter result (ied -> i, aing -> a etc),
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* step2 and step4 access the byte before the first letter. So we skip
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* steps after step1ab unless k > k0. */
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#include <string.h>
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#include "../lualib.h"
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#define TRUE 1
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#define FALSE 0
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/* The main part of the stemming algorithm starts here. b is a buffer
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* holding a word to be stemmed. The letters are in b[k0], b[k0+1] ...
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* ending at b[k]. In fact k0 = 0 in this demo program. k is readjusted
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* downwards as the stemming progresses. Zero termination is not in fact
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* used in the algorithm.
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*
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* Note that only lower case sequences are stemmed. Forcing to lower case
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* should be done before stem(...) is called. */
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/* buffer for word to be stemmed */
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static char *b;
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static int k;
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static int k0;
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/* j is a general offset into the string */
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static int j;
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/**
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* TRUE when `b[i]` is a consonant.
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*/
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static int
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isConsonant(int index) {
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switch (b[index]) {
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case 'a':
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case 'e':
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case 'i':
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case 'o':
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case 'u':
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return FALSE;
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case 'y':
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return (index == k0) ? TRUE : !isConsonant(index - 1);
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default:
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return TRUE;
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}
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}
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/* Measure the number of consonant sequences between
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* `k0` and `j`. If C is a consonant sequence and V
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* a vowel sequence, and <..> indicates arbitrary
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* presence:
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*
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* <C><V> gives 0
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* <C>VC<V> gives 1
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* <C>VCVC<V> gives 2
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* <C>VCVCVC<V> gives 3
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* ....
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*/
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static int
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getMeasure() {
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int position;
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int index;
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position = 0;
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index = k0;
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while (TRUE) {
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if (index > j) {
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return position;
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}
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if (!isConsonant(index)) {
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break;
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}
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index++;
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}
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index++;
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while (TRUE) {
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while (TRUE) {
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if (index > j) {
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return position;
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}
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if (isConsonant(index)) {
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break;
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}
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index++;
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}
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index++;
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position++;
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while (TRUE) {
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if (index > j) {
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return position;
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}
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if (!isConsonant(index)) {
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break;
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}
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index++;
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}
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index++;
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}
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}
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/* `TRUE` when `k0, ... j` contains a vowel. */
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static int
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vowelInStem() {
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int index;
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index = k0 - 1;
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while (++index <= j) {
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if (!isConsonant(index)) {
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return TRUE;
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}
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}
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return FALSE;
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}
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/* `TRUE` when `j` and `(j-1)` are the same consonant. */
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static int
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isDoubleConsonant(int index) {
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if (b[index] != b[index - 1]) {
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return FALSE;
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}
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return isConsonant(index);
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}
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/* `TRUE` when `i - 2, i - 1, i` has the form
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* `consonant - vowel - consonant` and also if the second
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* C is not `"w"`, `"x"`, or `"y"`. this is used when
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* trying to restore an `e` at the end of a short word.
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*
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* Such as:
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*
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* `cav(e)`, `lov(e)`, `hop(e)`, `crim(e)`, but `snow`,
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* `box`, `tray`.
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*/
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static int
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cvc(int index) {
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int character;
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if (index < k0 + 2 || !isConsonant(index) || isConsonant(index - 1) || !isConsonant(index - 2)) {
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return FALSE;
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}
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character = b[index];
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if (character == 'w' || character == 'x' || character == 'y') {
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return FALSE;
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}
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return TRUE;
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}
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/* `ends(s)` is `TRUE` when `k0, ...k` ends with `value`. */
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static int
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ends(const char *value) {
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int length = value[0];
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/* Tiny speed-up. */
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if (value[length] != b[k]) {
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return FALSE;
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}
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if (length > k - k0 + 1) {
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return FALSE;
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}
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if (memcmp(b + k - length + 1, value + 1, length) != 0) {
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return FALSE;
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}
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j = k - length;
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return TRUE;
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}
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/* `setTo(value)` sets `(j + 1), ...k` to the characters in
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* `value`, readjusting `k`. */
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static void
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setTo(const char *value) {
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int length = value[0];
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memmove(b + j + 1, value + 1, length);
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k = j + length;
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}
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/* Set string. */
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static void
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replace(const char *value) {
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if (getMeasure() > 0) {
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setTo(value);
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}
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}
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/* `step1ab()` gets rid of plurals, `-ed`, `-ing`.
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*
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* Such as:
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*
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* caresses -> caress
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* ponies -> poni
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* ties -> ti
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* caress -> caress
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* cats -> cat
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*
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* feed -> feed
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* agreed -> agree
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* disabled -> disable
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*
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* matting -> mat
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* mating -> mate
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* meeting -> meet
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* milling -> mill
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* messing -> mess
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*
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* meetings -> meet
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*/
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static void
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step1ab() {
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int character;
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if (b[k] == 's') {
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if (ends("\04" "sses")) {
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k -= 2;
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} else if (ends("\03" "ies")) {
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setTo("\01" "i");
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} else if (b[k - 1] != 's') {
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k--;
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}
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}
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if (ends("\03" "eed")) {
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if (getMeasure() > 0) {
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k--;
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}
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} else if ((ends("\02" "ed") || ends("\03" "ing")) && vowelInStem()) {
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k = j;
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if (ends("\02" "at")) {
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setTo("\03" "ate");
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} else if (ends("\02" "bl")) {
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setTo("\03" "ble");
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} else if (ends("\02" "iz")) {
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setTo("\03" "ize");
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} else if (isDoubleConsonant(k)) {
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k--;
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character = b[k];
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if (character == 'l' || character == 's' || character == 'z') {
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k++;
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}
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} else if (getMeasure() == 1 && cvc(k)) {
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setTo("\01" "e");
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}
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}
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}
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/* `step1c()` turns terminal `"y"` to `"i"` when there
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* is another vowel in the stem. */
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static void
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step1c() {
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if (ends("\01" "y") && vowelInStem()) {
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b[k] = 'i';
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}
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}
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/* `step2()` maps double suffices to single ones.
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* so -ization ( = -ize plus -ation) maps to -ize etc.
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* note that the string before the suffix must give
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* getMeasure() > 0. */
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static void
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step2() {
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switch (b[k - 1]) {
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case 'a':
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if (ends("\07" "ational")) {
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replace("\03" "ate");
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break;
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}
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if (ends("\06" "tional")) {
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replace("\04" "tion");
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break;
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}
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break;
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case 'c':
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if (ends("\04" "enci")) {
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replace("\04" "ence");
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break;
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}
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if (ends("\04" "anci")) {
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replace("\04" "ance");
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break;
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}
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break;
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case 'e':
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if (ends("\04" "izer")) {
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replace("\03" "ize");
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break;
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}
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break;
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case 'l':
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/* --DEPARTURE--: To match the published algorithm,
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* replace this line with:
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*
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* ```
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* if (ends("\04" "abli")) {
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* replace("\04" "able");
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*
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* break;
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* }
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* ```
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*/
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if (ends("\03" "bli")) {
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replace("\03" "ble");
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break;
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}
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if (ends("\04" "alli")) {
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replace("\02" "al");
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break;
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}
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if (ends("\05" "entli")) {
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replace("\03" "ent");
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break;
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}
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if (ends("\03" "eli")) {
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replace("\01" "e");
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break;
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}
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if (ends("\05" "ousli")) {
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replace("\03" "ous");
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break;
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}
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break;
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case 'o':
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if (ends("\07" "ization")) {
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replace("\03" "ize");
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break;
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}
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if (ends("\05" "ation")) {
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replace("\03" "ate");
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break;
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}
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if (ends("\04" "ator")) {
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replace("\03" "ate");
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break;
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}
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break;
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case 's':
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if (ends("\05" "alism")) {
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replace("\02" "al");
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break;
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}
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if (ends("\07" "iveness")) {
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replace("\03" "ive");
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break;
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}
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if (ends("\07" "fulness")) {
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replace("\03" "ful");
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break;
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}
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if (ends("\07" "ousness")) {
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replace("\03" "ous");
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break;
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}
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break;
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case 't':
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if (ends("\05" "aliti")) {
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replace("\02" "al");
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break;
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}
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if (ends("\05" "iviti")) {
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replace("\03" "ive");
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break;
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}
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if (ends("\06" "biliti")) {
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replace("\03" "ble");
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break;
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}
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break;
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/* --DEPARTURE--: To match the published algorithm, delete this line. */
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case 'g':
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if (ends("\04" "logi")) {
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replace("\03" "log");
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break;
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}
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}
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}
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/* `step3()` deals with -ic-, -full, -ness etc.
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* similar strategy to step2. */
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static void
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step3() {
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switch (b[k]) {
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case 'e':
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if (ends("\05" "icate")) {
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replace("\02" "ic");
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break;
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}
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if (ends("\05" "ative")) {
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replace("\00" "");
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break;
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}
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if (ends("\05" "alize")) {
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replace("\02" "al");
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break;
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}
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break;
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case 'i':
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if (ends("\05" "iciti")) {
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replace("\02" "ic");
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break;
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}
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break;
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case 'l':
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if (ends("\04" "ical")) {
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replace("\02" "ic");
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break;
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}
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if (ends("\03" "ful")) {
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replace("\00" "");
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break;
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}
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break;
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case 's':
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if (ends("\04" "ness")) {
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replace("\00" "");
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break;
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}
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break;
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}
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}
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/* `step4()` takes off -ant, -ence etc., in
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* context <c>vcvc<v>. */
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static void
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step4() {
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switch (b[k - 1]) {
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case 'a':
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if (ends("\02" "al")) {
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break;
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}
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return;
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case 'c':
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if (ends("\04" "ance")) {
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break;
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}
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if (ends("\04" "ence")) {
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break;
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}
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return;
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case 'e':
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if (ends("\02" "er")) {
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break;
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}
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return;
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case 'i':
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if (ends("\02" "ic")) {
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break;
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}
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return;
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case 'l':
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if (ends("\04" "able")) {
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break;
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}
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if (ends("\04" "ible")) {
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break;
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}
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return;
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case 'n':
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if (ends("\03" "ant")) {
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break;
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}
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if (ends("\05" "ement")) {
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break;
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}
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if (ends("\04" "ment")) {
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break;
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}
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if (ends("\03" "ent")) {
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break;
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}
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return;
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case 'o':
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if (ends("\03" "ion") && j >= k0 && (b[j] == 's' || b[j] == 't')) {
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break;
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}
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/* takes care of -ous */
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if (ends("\02" "ou")) {
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break;
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}
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return;
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case 's':
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if (ends("\03" "ism")) {
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break;
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}
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return;
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case 't':
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if (ends("\03" "ate")) {
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break;
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}
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if (ends("\03" "iti")) {
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break;
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}
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return;
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case 'u':
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if (ends("\03" "ous")) {
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break;
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}
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return;
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case 'v':
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if (ends("\03" "ive")) {
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break;
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}
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return;
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case 'z':
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if (ends("\03" "ize")) {
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break;
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}
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return;
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default:
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return;
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}
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if (getMeasure() > 1) {
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k = j;
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}
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}
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/* `step5()` removes a final `-e` if `getMeasure()` is
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* greater than `1`, and changes `-ll` to `-l` if
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* `getMeasure()` is greater than `1`. */
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static void
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step5() {
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int a;
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j = k;
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if (b[k] == 'e') {
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a = getMeasure();
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if (a > 1 || (a == 1 && !cvc(k - 1))) {
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k--;
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}
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}
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|
if (b[k] == 'l' && isDoubleConsonant(k) && getMeasure() > 1) {
|
|
k--;
|
|
}
|
|
}
|
|
|
|
/* In `stem(p, i, j)`, `p` is a `char` pointer, and the
|
|
* string to be stemmed is from `p[i]` to
|
|
* `p[j]` (inclusive).
|
|
*
|
|
* Typically, `i` is zero and `j` is the offset to the
|
|
* last character of a string, `(p[j + 1] == '\0')`.
|
|
* The stemmer adjusts the characters `p[i]` ... `p[j]`
|
|
* and returns the new end-point of the string, `k`.
|
|
*
|
|
* Stemming never increases word length, so `i <= k <= j`.
|
|
*
|
|
* To turn the stemmer into a module, declare 'stem' as
|
|
* extern, and delete the remainder of this file. */
|
|
int
|
|
stem(char *p, int index, int position) {
|
|
/* Copy the parameters into statics. */
|
|
b = p;
|
|
k = position;
|
|
k0 = index;
|
|
|
|
if (k <= k0 + 1) {
|
|
return k; /* --DEPARTURE-- */
|
|
}
|
|
|
|
/* With this line, strings of length 1 or 2 don't
|
|
* go through the stemming process, although no
|
|
* mention is made of this in the published
|
|
* algorithm. Remove the line to match the published
|
|
* algorithm. */
|
|
step1ab();
|
|
|
|
if (k > k0) {
|
|
step1c();
|
|
step2();
|
|
step3();
|
|
step4();
|
|
step5();
|
|
}
|
|
|
|
return k;
|
|
}
|
|
|
|
|
|
static int l_stmr(lua_State* L)
|
|
{
|
|
char* word = strdup(luaL_checkstring(L,1));
|
|
int end = stem(word, 0, strlen(word) - 1);
|
|
word[end + 1] = 0;
|
|
lua_pushstring(L, word);
|
|
free(word);
|
|
return 1;
|
|
}
|
|
|
|
static const struct luaL_Reg _lib [] = {
|
|
{"stmr", l_stmr},
|
|
{NULL,NULL}
|
|
};
|
|
|
|
int luaopen_stmr(lua_State *L)
|
|
{
|
|
luaL_newlib(L, _lib);
|
|
return 1;
|
|
} |