Mercurial > hg > CbC > CbC_gcc
comparison gcc/spellcheck.c @ 111:04ced10e8804
gcc 7
author | kono |
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date | Fri, 27 Oct 2017 22:46:09 +0900 |
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children | 84e7813d76e9 |
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1 /* Find near-matches for strings. | |
2 Copyright (C) 2015-2017 Free Software Foundation, Inc. | |
3 | |
4 This file is part of GCC. | |
5 | |
6 GCC is free software; you can redistribute it and/or modify it under | |
7 the terms of the GNU General Public License as published by the Free | |
8 Software Foundation; either version 3, or (at your option) any later | |
9 version. | |
10 | |
11 GCC is distributed in the hope that it will be useful, but WITHOUT ANY | |
12 WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
13 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | |
14 for more details. | |
15 | |
16 You should have received a copy of the GNU General Public License | |
17 along with GCC; see the file COPYING3. If not see | |
18 <http://www.gnu.org/licenses/>. */ | |
19 | |
20 #include "config.h" | |
21 #include "system.h" | |
22 #include "coretypes.h" | |
23 #include "tm.h" | |
24 #include "tree.h" | |
25 #include "spellcheck.h" | |
26 #include "selftest.h" | |
27 | |
28 /* The Levenshtein distance is an "edit-distance": the minimal | |
29 number of one-character insertions, removals or substitutions | |
30 that are needed to change one string into another. | |
31 | |
32 This implementation uses the Wagner-Fischer algorithm. */ | |
33 | |
34 edit_distance_t | |
35 levenshtein_distance (const char *s, int len_s, | |
36 const char *t, int len_t) | |
37 { | |
38 const bool debug = false; | |
39 | |
40 if (debug) | |
41 { | |
42 printf ("s: \"%s\" (len_s=%i)\n", s, len_s); | |
43 printf ("t: \"%s\" (len_t=%i)\n", t, len_t); | |
44 } | |
45 | |
46 if (len_s == 0) | |
47 return len_t; | |
48 if (len_t == 0) | |
49 return len_s; | |
50 | |
51 /* We effectively build a matrix where each (i, j) contains the | |
52 Levenshtein distance between the prefix strings s[0:j] | |
53 and t[0:i]. | |
54 Rather than actually build an (len_t + 1) * (len_s + 1) matrix, | |
55 we simply keep track of the last row, v0 and a new row, v1, | |
56 which avoids an (len_t + 1) * (len_s + 1) allocation and memory accesses | |
57 in favor of two (len_s + 1) allocations. These could potentially be | |
58 statically-allocated if we impose a maximum length on the | |
59 strings of interest. */ | |
60 edit_distance_t *v0 = new edit_distance_t[len_s + 1]; | |
61 edit_distance_t *v1 = new edit_distance_t[len_s + 1]; | |
62 | |
63 /* The first row is for the case of an empty target string, which | |
64 we can reach by deleting every character in the source string. */ | |
65 for (int i = 0; i < len_s + 1; i++) | |
66 v0[i] = i; | |
67 | |
68 /* Build successive rows. */ | |
69 for (int i = 0; i < len_t; i++) | |
70 { | |
71 if (debug) | |
72 { | |
73 printf ("i:%i v0 = ", i); | |
74 for (int j = 0; j < len_s + 1; j++) | |
75 printf ("%i ", v0[j]); | |
76 printf ("\n"); | |
77 } | |
78 | |
79 /* The initial column is for the case of an empty source string; we | |
80 can reach prefixes of the target string of length i | |
81 by inserting i characters. */ | |
82 v1[0] = i + 1; | |
83 | |
84 /* Build the rest of the row by considering neighbors to | |
85 the north, west and northwest. */ | |
86 for (int j = 0; j < len_s; j++) | |
87 { | |
88 edit_distance_t cost = (s[j] == t[i] ? 0 : 1); | |
89 edit_distance_t deletion = v1[j] + 1; | |
90 edit_distance_t insertion = v0[j + 1] + 1; | |
91 edit_distance_t substitution = v0[j] + cost; | |
92 edit_distance_t cheapest = MIN (deletion, insertion); | |
93 cheapest = MIN (cheapest, substitution); | |
94 v1[j + 1] = cheapest; | |
95 } | |
96 | |
97 /* Prepare to move on to next row. */ | |
98 for (int j = 0; j < len_s + 1; j++) | |
99 v0[j] = v1[j]; | |
100 } | |
101 | |
102 if (debug) | |
103 { | |
104 printf ("final v1 = "); | |
105 for (int j = 0; j < len_s + 1; j++) | |
106 printf ("%i ", v1[j]); | |
107 printf ("\n"); | |
108 } | |
109 | |
110 edit_distance_t result = v1[len_s]; | |
111 delete[] v0; | |
112 delete[] v1; | |
113 return result; | |
114 } | |
115 | |
116 /* Calculate Levenshtein distance between two nil-terminated strings. */ | |
117 | |
118 edit_distance_t | |
119 levenshtein_distance (const char *s, const char *t) | |
120 { | |
121 return levenshtein_distance (s, strlen (s), t, strlen (t)); | |
122 } | |
123 | |
124 /* Given TARGET, a non-NULL string, and CANDIDATES, a non-NULL ptr to | |
125 an autovec of non-NULL strings, determine which element within | |
126 CANDIDATES has the lowest edit distance to TARGET. If there are | |
127 multiple elements with the same minimal distance, the first in the | |
128 vector wins. | |
129 | |
130 If more than half of the letters were misspelled, the suggestion is | |
131 likely to be meaningless, so return NULL for this case. */ | |
132 | |
133 const char * | |
134 find_closest_string (const char *target, | |
135 const auto_vec<const char *> *candidates) | |
136 { | |
137 gcc_assert (target); | |
138 gcc_assert (candidates); | |
139 | |
140 int i; | |
141 const char *candidate; | |
142 best_match<const char *, const char *> bm (target); | |
143 FOR_EACH_VEC_ELT (*candidates, i, candidate) | |
144 { | |
145 gcc_assert (candidate); | |
146 bm.consider (candidate); | |
147 } | |
148 | |
149 return bm.get_best_meaningful_candidate (); | |
150 } | |
151 | |
152 #if CHECKING_P | |
153 | |
154 namespace selftest { | |
155 | |
156 /* Selftests. */ | |
157 | |
158 /* Verify that the levenshtein_distance (A, B) equals the expected | |
159 value. */ | |
160 | |
161 static void | |
162 levenshtein_distance_unit_test_oneway (const char *a, const char *b, | |
163 edit_distance_t expected) | |
164 { | |
165 edit_distance_t actual = levenshtein_distance (a, b); | |
166 ASSERT_EQ (actual, expected); | |
167 } | |
168 | |
169 /* Verify that both | |
170 levenshtein_distance (A, B) | |
171 and | |
172 levenshtein_distance (B, A) | |
173 equal the expected value, to ensure that the function is symmetric. */ | |
174 | |
175 static void | |
176 levenshtein_distance_unit_test (const char *a, const char *b, | |
177 edit_distance_t expected) | |
178 { | |
179 levenshtein_distance_unit_test_oneway (a, b, expected); | |
180 levenshtein_distance_unit_test_oneway (b, a, expected); | |
181 } | |
182 | |
183 /* Verify that find_closest_string is sane. */ | |
184 | |
185 static void | |
186 test_find_closest_string () | |
187 { | |
188 auto_vec<const char *> candidates; | |
189 | |
190 /* Verify that it can handle an empty vec. */ | |
191 ASSERT_EQ (NULL, find_closest_string ("", &candidates)); | |
192 | |
193 /* Verify that it works sanely for non-empty vecs. */ | |
194 candidates.safe_push ("apple"); | |
195 candidates.safe_push ("banana"); | |
196 candidates.safe_push ("cherry"); | |
197 | |
198 ASSERT_STREQ ("apple", find_closest_string ("app", &candidates)); | |
199 ASSERT_STREQ ("banana", find_closest_string ("banyan", &candidates)); | |
200 ASSERT_STREQ ("cherry", find_closest_string ("berry", &candidates)); | |
201 ASSERT_EQ (NULL, find_closest_string ("not like the others", &candidates)); | |
202 | |
203 /* The order of the vec can matter, but it should not matter for these | |
204 inputs. */ | |
205 candidates.truncate (0); | |
206 candidates.safe_push ("cherry"); | |
207 candidates.safe_push ("banana"); | |
208 candidates.safe_push ("apple"); | |
209 ASSERT_STREQ ("apple", find_closest_string ("app", &candidates)); | |
210 ASSERT_STREQ ("banana", find_closest_string ("banyan", &candidates)); | |
211 ASSERT_STREQ ("cherry", find_closest_string ("berry", &candidates)); | |
212 ASSERT_EQ (NULL, find_closest_string ("not like the others", &candidates)); | |
213 | |
214 /* If the goal string somehow makes it into the candidate list, offering | |
215 it as a suggestion will be nonsensical. Verify that we don't offer such | |
216 suggestions. */ | |
217 ASSERT_EQ (NULL, find_closest_string ("banana", &candidates)); | |
218 } | |
219 | |
220 /* Test data for test_metric_conditions. */ | |
221 | |
222 static const char * const test_data[] = { | |
223 "", | |
224 "foo", | |
225 "food", | |
226 "boo", | |
227 "1234567890123456789012345678901234567890123456789012345678901234567890" | |
228 }; | |
229 | |
230 /* Verify that levenshtein_distance appears to be a sane distance function, | |
231 i.e. the conditions for being a metric. This is done directly for a | |
232 small set of examples, using test_data above. This is O(N^3) in the size | |
233 of the array, due to the test for the triangle inequality, so we keep the | |
234 array small. */ | |
235 | |
236 static void | |
237 test_metric_conditions () | |
238 { | |
239 const int num_test_cases = sizeof (test_data) / sizeof (test_data[0]); | |
240 | |
241 for (int i = 0; i < num_test_cases; i++) | |
242 { | |
243 for (int j = 0; j < num_test_cases; j++) | |
244 { | |
245 edit_distance_t dist_ij | |
246 = levenshtein_distance (test_data[i], test_data[j]); | |
247 | |
248 /* Identity of indiscernibles: d(i, j) > 0 iff i == j. */ | |
249 if (i == j) | |
250 ASSERT_EQ (dist_ij, 0); | |
251 else | |
252 ASSERT_TRUE (dist_ij > 0); | |
253 | |
254 /* Symmetry: d(i, j) == d(j, i). */ | |
255 edit_distance_t dist_ji | |
256 = levenshtein_distance (test_data[j], test_data[i]); | |
257 ASSERT_EQ (dist_ij, dist_ji); | |
258 | |
259 /* Triangle inequality. */ | |
260 for (int k = 0; k < num_test_cases; k++) | |
261 { | |
262 edit_distance_t dist_ik | |
263 = levenshtein_distance (test_data[i], test_data[k]); | |
264 edit_distance_t dist_jk | |
265 = levenshtein_distance (test_data[j], test_data[k]); | |
266 ASSERT_TRUE (dist_ik <= dist_ij + dist_jk); | |
267 } | |
268 } | |
269 } | |
270 } | |
271 | |
272 /* Verify levenshtein_distance for a variety of pairs of pre-canned | |
273 inputs, comparing against known-good values. */ | |
274 | |
275 void | |
276 spellcheck_c_tests () | |
277 { | |
278 levenshtein_distance_unit_test ("", "nonempty", strlen ("nonempty")); | |
279 levenshtein_distance_unit_test ("saturday", "sunday", 3); | |
280 levenshtein_distance_unit_test ("foo", "m_foo", 2); | |
281 levenshtein_distance_unit_test ("hello_world", "HelloWorld", 3); | |
282 levenshtein_distance_unit_test | |
283 ("the quick brown fox jumps over the lazy dog", "dog", 40); | |
284 levenshtein_distance_unit_test | |
285 ("the quick brown fox jumps over the lazy dog", | |
286 "the quick brown dog jumps over the lazy fox", | |
287 4); | |
288 levenshtein_distance_unit_test | |
289 ("Lorem ipsum dolor sit amet, consectetur adipiscing elit,", | |
290 "All your base are belong to us", | |
291 44); | |
292 levenshtein_distance_unit_test ("foo", "FOO", 3); | |
293 | |
294 test_find_closest_string (); | |
295 test_metric_conditions (); | |
296 } | |
297 | |
298 } // namespace selftest | |
299 | |
300 #endif /* #if CHECKING_P */ |