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26 * This is a very clever method for correcting mistakes in QuakeC code
27 * most notably when invalid identifiers are used or inproper assignments;
28 * we can proprly lookup in multiple dictonaries (depening on the rules
29 * of what the task is trying to acomplish) to find the best possible
33 * A little about how it works, and probability theory:
35 * When given an identifier (which we will denote I), we're essentially
36 * just trying to choose the most likely correction for that identifier.
37 * (the actual "correction" can very well be the identifier itself).
38 * There is actually no way to know for sure that certian identifers
39 * such as "lates", need to be corrected to "late" or "latest" or any
40 * other permutations that look lexically the same. This is why we
41 * must advocate the usage of probabilities. This implies that we're
42 * trying to find the correction for C, out of all possible corrections
43 * that maximizes the probability of C for the original identifer I.
45 * Bayes' Therom suggests something of the following:
46 * AC P(I|C) P(C) / P(I)
47 * Since P(I) is the same for every possibly I, we can ignore it giving
50 * This greatly helps visualize how the parts of the expression are performed
51 * there is essentially three, from right to left we perform the following:
53 * 1: P(C), the probability that a proposed correction C will stand on its
54 * own. This is called the language model.
56 * 2: P(I|C), the probability that I would be used, when the programmer
57 * really meant C. This is the error model.
59 * 3: AC, the control mechanisim, which implies the enumeration of all
60 * feasible values of C, and then determine the one that gives the
61 * greatest probability score. Selecting it as the "correction"
64 * The requirement for complex expression involving two models:
66 * In reality the requirement for a more complex expression involving
67 * two seperate models is considerably a waste. But one must recognize
68 * that P(C|I) is already conflating two factors. It's just much simpler
69 * to seperate the two models and deal with them explicitaly. To properly
70 * estimate P(C|I) you have to consider both the probability of C and
71 * probability of the transposition from C to I. It's simply much more
72 * cleaner, and direct to seperate the two factors.
75 /* some hashtable management for dictonaries */
76 static size_t *correct_find(ht table, const char *word) {
77 return (size_t*)util_htget(table, word);
80 static int correct_update(ht *table, const char *word) {
81 size_t *data = correct_find(*table, word);
91 * _ is valid in identifiers. I've yet to implement numerics however
92 * because they're only valid after the first character is of a _, or
95 static const char correct_alpha[] = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_";
96 static char *correct_substr(const char *str, size_t off, size_t lim) {
98 size_t slen = strlen(str);
100 /* lots of compares */
101 if ((lim > slen) || ((off + lim) > slen) || (slen < 1) || (!lim))
104 if (!(nstr = mem_a(lim + 1)))
107 strncpy(nstr, str+off, lim);
113 static char *correct_concat(char *str1, char *str2) {
114 if (!str1) str1 = mem_a(1), *str1 = '\0';
115 if (!str2) str2 = mem_a(1), *str2 = '\0';
117 str1 = mem_r(str1, strlen(str1) + strlen(str2) + 1);
124 * correcting logic for the following forms of transformations:
130 static size_t correct_deletion(const char *ident, char **array, size_t index) {
132 size_t len = strlen(ident);
134 for (itr = 0; itr < len; itr++) {
135 array[index + itr] = correct_concat (
136 correct_substr (ident, 0, itr),
137 correct_substr (ident, itr+1, len-(itr+1))
144 static size_t correct_transposition(const char *ident, char **array, size_t index) {
146 size_t len = strlen(ident);
148 for (itr = 0; itr < len - 1; itr++) {
149 array[index + itr] = correct_concat (
151 correct_substr(ident, 0, itr),
152 correct_substr(ident, itr+1, 1)
155 correct_substr(ident, itr, 1),
156 correct_substr(ident, itr+2, len-(itr+2))
164 static size_t correct_alteration(const char *ident, char **array, size_t index) {
168 size_t len = strlen(ident);
169 char cct[2] = { 0, 0 }; /* char code table, for concatenation */
171 for (itr = 0, ktr = 0; itr < len; itr++) {
172 for (jtr = 0; jtr < sizeof(correct_alpha); jtr++, ktr++) {
173 *cct = correct_alpha[jtr];
174 array[index + ktr] = correct_concat (
176 correct_substr(ident, 0, itr),
191 static size_t correct_insertion(const char *ident, char **array, size_t index) {
195 size_t len = strlen(ident);
196 char cct[2] = { 0, 0 }; /* char code table, for concatenation */
198 for (itr = 0, ktr = 0; itr <= len; itr++) {
199 for (jtr = 0; jtr < sizeof(correct_alpha); jtr++, ktr++) {
200 *cct = correct_alpha[jtr];
201 array[index + ktr] = correct_concat (
203 correct_substr (ident, 0, itr),
218 static GMQCC_INLINE size_t correct_size(const char *ident) {
221 * transposition = len - 1
222 * alteration = len * sizeof(correct_alpha)
223 * insertion = (len + 1) * sizeof(correct_alpha)
226 register size_t len = strlen(ident);
227 return (len) + (len - 1) + (len * sizeof(correct_alpha)) + (len + 1) * sizeof(correct_alpha);
230 static char **correct_edit(const char *ident) {
232 char **find = mem_a(correct_size(ident) * sizeof(char*));
237 next = correct_deletion (ident, find, 0);
238 next += correct_transposition(ident, find, next);
239 next += correct_alteration (ident, find, next);
240 /*****/ correct_insertion (ident, find, next);
246 * We could use a hashtable but the space complexity isn't worth it
247 * since we're only going to determine the "did you mean?" identifier
250 static int correct_exist(char **array, size_t rows, char *ident) {
252 for (itr = 0; itr < rows; itr++)
253 if (!strcmp(array[itr], ident))
259 static char **correct_known(ht table, char **array, size_t rows, size_t *next) {
267 for (itr = 0, len = 0; itr < rows; itr++) {
268 end = correct_edit(array[itr]);
269 row = correct_size(array[itr]);
271 for (jtr = 0; jtr < row; jtr++) {
272 if (correct_find(table, end[jtr]) && !correct_exist(res, len, end[jtr])) {
273 res = mem_r(res, sizeof(char*) * (len + 1));
274 res[len++] = end[jtr];
283 static char *correct_maximum(ht table, char **array, size_t rows) {
289 for (itr = 0, top = 0; itr < rows; itr++) {
290 if ((itm = correct_find(table, array[itr])) && (*itm > top)) {
299 static void correct_cleanup(char **array, size_t rows) {
301 for (itr = 0; itr < rows; itr++)
306 * This is the exposed interface:
307 * takes a table for the dictonary a vector of sizes (used for internal
308 * probability calculation, and an identifier to "correct"
310 * the add function works the same. Except the identifier is used to
311 * add to the dictonary.
313 void correct_add(ht table, size_t ***size, const char *ident) {
315 const char *add = ident;
317 if (!correct_update(&table, add)) {
318 data = (size_t*)mem_a(sizeof(size_t));
321 vec_push((*size), data);
322 util_htset(table, add, data);
326 char *correct_correct(ht table, const char *ident) {
331 char *found = util_strdup(ident);
336 /* needs to be allocated for free later */
337 if (correct_find(table, ident))
341 if ((e1rows = correct_size(ident))) {
342 e1 = correct_edit(ident);
344 if ((e1ident = correct_maximum(table, e1, e1rows))) {
345 found = util_strdup(e1ident);
346 correct_cleanup(e1, e1rows);
352 e2 = correct_known(table, e1, e1rows, &e2rows);
353 if (e2rows && ((e2ident = correct_maximum(table, e2, e2rows))))
354 found = util_strdup(e2ident);
356 correct_cleanup(e1, e1rows);
357 correct_cleanup(e2, e2rows);
365 void correct_del(ht dictonary, size_t **data) {
367 for (i = 0; i < vec_size(data); i++)
371 util_htdel(dictonary);
379 ht t = util_htnew(1024);
382 correct_add(t, &d, "hellobain");
383 correct_add(t, &d, "ellor");
384 correct_add(t, &d, "world");
386 printf("found identifiers: (2)\n");
387 printf(" 1: hello\n");
388 printf(" 2: world\n");
390 char *b = correct_correct(t, "rld");
391 char *a = correct_correct(t, "ello");
393 printf("%s, did you mean `%s` ?\n", "ello", a);
394 printf("%s, did you mean `%s` ?\n", "rld", b);