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500 lines
16 KiB
C
500 lines
16 KiB
C
/* Find near-matches for strings.
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Copyright (C) 2015-2019 Free Software Foundation, Inc.
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This file is part of GCC.
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GCC is free software; you can redistribute it and/or modify it under
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the terms of the GNU General Public License as published by the Free
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Software Foundation; either version 3, or (at your option) any later
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version.
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GCC is distributed in the hope that it will be useful, but WITHOUT ANY
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WARRANTY; without even the implied warranty of MERCHANTABILITY or
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FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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for more details.
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You should have received a copy of the GNU General Public License
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along with GCC; see the file COPYING3. If not see
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<http://www.gnu.org/licenses/>. */
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#include "config.h"
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#include "system.h"
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#include "coretypes.h"
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#include "tm.h"
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#include "tree.h"
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#include "spellcheck.h"
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#include "selftest.h"
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/* Get the edit distance between the two strings: the minimal
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number of edits that are needed to change one string into another,
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where edits can be one-character insertions, removals, or substitutions,
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or transpositions of two adjacent characters (counting as one "edit").
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This implementation uses the Wagner-Fischer algorithm for the
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Damerau-Levenshtein distance; specifically, the "optimal string alignment
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distance" or "restricted edit distance" variant. */
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edit_distance_t
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get_edit_distance (const char *s, int len_s,
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const char *t, int len_t)
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{
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const bool debug = false;
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if (debug)
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{
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printf ("s: \"%s\" (len_s=%i)\n", s, len_s);
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printf ("t: \"%s\" (len_t=%i)\n", t, len_t);
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}
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if (len_s == 0)
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return len_t;
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if (len_t == 0)
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return len_s;
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/* We effectively build a matrix where each (i, j) contains the
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distance between the prefix strings s[0:j] and t[0:i].
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Rather than actually build an (len_t + 1) * (len_s + 1) matrix,
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we simply keep track of the last two rows, v_one_ago and v_two_ago,
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and a new row, v_next, which avoids an (len_t + 1) * (len_s + 1)
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allocation and memory accesses in favor of three (len_s + 1)
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allocations. These could potentially be
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statically-allocated if we impose a maximum length on the
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strings of interest. */
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edit_distance_t *v_two_ago = new edit_distance_t[len_s + 1];
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edit_distance_t *v_one_ago = new edit_distance_t[len_s + 1];
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edit_distance_t *v_next = new edit_distance_t[len_s + 1];
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/* The first row is for the case of an empty target string, which
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we can reach by deleting every character in the source string. */
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for (int i = 0; i < len_s + 1; i++)
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v_one_ago[i] = i;
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/* Build successive rows. */
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for (int i = 0; i < len_t; i++)
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{
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if (debug)
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{
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printf ("i:%i v_one_ago = ", i);
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for (int j = 0; j < len_s + 1; j++)
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printf ("%i ", v_one_ago[j]);
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printf ("\n");
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}
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/* The initial column is for the case of an empty source string; we
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can reach prefixes of the target string of length i
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by inserting i characters. */
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v_next[0] = i + 1;
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/* Build the rest of the row by considering neighbors to
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the north, west and northwest. */
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for (int j = 0; j < len_s; j++)
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{
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edit_distance_t cost = (s[j] == t[i] ? 0 : 1);
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edit_distance_t deletion = v_next[j] + 1;
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edit_distance_t insertion = v_one_ago[j + 1] + 1;
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edit_distance_t substitution = v_one_ago[j] + cost;
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edit_distance_t cheapest = MIN (deletion, insertion);
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cheapest = MIN (cheapest, substitution);
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if (i > 0 && j > 0 && s[j] == t[i - 1] && s[j - 1] == t[i])
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{
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edit_distance_t transposition = v_two_ago[j - 1] + 1;
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cheapest = MIN (cheapest, transposition);
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}
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v_next[j + 1] = cheapest;
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}
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/* Prepare to move on to next row. */
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for (int j = 0; j < len_s + 1; j++)
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{
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v_two_ago[j] = v_one_ago[j];
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v_one_ago[j] = v_next[j];
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}
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}
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if (debug)
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{
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printf ("final v_next = ");
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for (int j = 0; j < len_s + 1; j++)
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printf ("%i ", v_next[j]);
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printf ("\n");
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}
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edit_distance_t result = v_next[len_s];
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delete[] v_two_ago;
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delete[] v_one_ago;
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delete[] v_next;
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return result;
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}
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/* Get the edit distance between two nil-terminated strings. */
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edit_distance_t
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get_edit_distance (const char *s, const char *t)
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{
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return get_edit_distance (s, strlen (s), t, strlen (t));
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}
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/* Given TARGET, a non-NULL string, and CANDIDATES, a non-NULL ptr to
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an autovec of non-NULL strings, determine which element within
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CANDIDATES has the lowest edit distance to TARGET. If there are
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multiple elements with the same minimal distance, the first in the
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vector wins.
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If more than half of the letters were misspelled, the suggestion is
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likely to be meaningless, so return NULL for this case. */
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const char *
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find_closest_string (const char *target,
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const auto_vec<const char *> *candidates)
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{
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gcc_assert (target);
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gcc_assert (candidates);
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int i;
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const char *candidate;
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best_match<const char *, const char *> bm (target);
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FOR_EACH_VEC_ELT (*candidates, i, candidate)
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{
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gcc_assert (candidate);
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bm.consider (candidate);
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}
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return bm.get_best_meaningful_candidate ();
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}
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/* Generate the maximum edit distance for which we consider a suggestion
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to be meaningful, given a goal of length GOAL_LEN and a candidate of
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length CANDIDATE_LEN.
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This is a third of the the length of the candidate or of the goal,
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whichever is bigger. */
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edit_distance_t
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get_edit_distance_cutoff (size_t goal_len, size_t candidate_len)
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{
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size_t max_length = MAX (goal_len, candidate_len);
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size_t min_length = MIN (goal_len, candidate_len);
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gcc_assert (max_length >= min_length);
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/* Special case: don't offer suggestions for a pair of
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length == 1 strings (or empty strings). */
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if (max_length <= 1)
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return 0;
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/* If the lengths are close, then round down. */
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if (max_length - min_length <= 1)
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/* ...but allow an edit distance of at least 1. */
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return MAX (max_length / 3, 1);
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/* Otherwise, round up (thus giving a little extra leeway to some cases
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involving insertions/deletions). */
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return (max_length + 2) / 3;
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}
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#if CHECKING_P
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namespace selftest {
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/* Selftests. */
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/* Verify that get_edit_distance (A, B) equals the expected value. */
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static void
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test_get_edit_distance_one_way (const char *a, const char *b,
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edit_distance_t expected)
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{
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edit_distance_t actual = get_edit_distance (a, b);
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ASSERT_EQ (actual, expected);
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}
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/* Verify that both
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get_edit_distance (A, B)
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and
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get_edit_distance (B, A)
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equal the expected value, to ensure that the function is symmetric. */
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static void
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test_get_edit_distance_both_ways (const char *a, const char *b,
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edit_distance_t expected)
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{
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test_get_edit_distance_one_way (a, b, expected);
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test_get_edit_distance_one_way (b, a, expected);
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}
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/* Verify get_edit_distance for a variety of pairs of pre-canned
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inputs, comparing against known-good values. */
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static void
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test_edit_distances ()
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{
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test_get_edit_distance_both_ways ("", "nonempty", strlen ("nonempty"));
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test_get_edit_distance_both_ways ("saturday", "sunday", 3);
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test_get_edit_distance_both_ways ("foo", "m_foo", 2);
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test_get_edit_distance_both_ways ("hello_world", "HelloWorld", 3);
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test_get_edit_distance_both_ways
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("the quick brown fox jumps over the lazy dog", "dog", 40);
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test_get_edit_distance_both_ways
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("the quick brown fox jumps over the lazy dog",
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"the quick brown dog jumps over the lazy fox",
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4);
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test_get_edit_distance_both_ways
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("Lorem ipsum dolor sit amet, consectetur adipiscing elit,",
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"All your base are belong to us",
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44);
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test_get_edit_distance_both_ways ("foo", "FOO", 3);
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test_get_edit_distance_both_ways ("fee", "deed", 2);
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test_get_edit_distance_both_ways ("coorzd1", "coordx1", 2);
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test_get_edit_distance_both_ways ("assert", "sqrt", 3);
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test_get_edit_distance_both_ways ("PATH_MAX", "INT8_MAX", 3);
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test_get_edit_distance_both_ways ("time", "nice", 2);
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test_get_edit_distance_both_ways ("bar", "carg", 2);
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test_get_edit_distance_both_ways ("gtk_widget_show_all",
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"GtkWidgetShowAll", 7);
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test_get_edit_distance_both_ways ("m_bar", "bar", 2);
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test_get_edit_distance_both_ways ("MACRO", "MACRAME", 3);
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test_get_edit_distance_both_ways ("ab", "ac", 1);
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test_get_edit_distance_both_ways ("ab", "a", 1);
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test_get_edit_distance_both_ways ("a", "b", 1);
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test_get_edit_distance_both_ways ("nanl", "name", 2);
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test_get_edit_distance_both_ways ("char", "bar", 2);
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test_get_edit_distance_both_ways ("-optimize", "fsanitize", 5);
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test_get_edit_distance_both_ways ("__DATE__", "__i386__", 4);
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/* Examples where transposition helps. */
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test_get_edit_distance_both_ways ("ab", "ba", 1);
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test_get_edit_distance_both_ways ("ba", "abc", 2);
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test_get_edit_distance_both_ways ("coorzd1", "coordz1", 1);
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test_get_edit_distance_both_ways ("abcdefghijklmnopqrstuvwxyz",
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"bacdefghijklmnopqrstuvwxzy", 2);
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test_get_edit_distance_both_ways ("saturday", "sundya", 4);
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test_get_edit_distance_both_ways ("signed", "singed", 1);
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}
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/* Subroutine of test_get_edit_distance_cutoff, for emulating the
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spellchecking cutoff in up to GCC 8. */
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static edit_distance_t
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get_old_cutoff (size_t goal_len, size_t candidate_len)
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{
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return MAX (goal_len, candidate_len) / 2;
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}
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/* Verify that the cutoff for "meaningfulness" of suggestions is at least as
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conservative as in older GCC releases.
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This should ensure that we don't offer additional meaningless
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suggestions (apart from those for which transposition has helped). */
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static void
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test_get_edit_distance_cutoff ()
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{
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for (size_t goal_len = 0; goal_len < 30; goal_len++)
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for (size_t candidate_len = 0; candidate_len < 30; candidate_len++)
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ASSERT_TRUE (get_edit_distance_cutoff (goal_len, candidate_len)
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<= get_old_cutoff (goal_len, candidate_len));
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}
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/* Assert that CANDIDATE is offered as a suggestion for TARGET. */
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static void
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assert_suggested_for (const location &loc, const char *candidate,
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const char *target)
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{
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auto_vec<const char *> candidates;
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candidates.safe_push (candidate);
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ASSERT_EQ_AT (loc, candidate, find_closest_string (target, &candidates));
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}
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/* Assert that CANDIDATE is offered as a suggestion for TARGET. */
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#define ASSERT_SUGGESTED_FOR(CANDIDATE, TARGET) \
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SELFTEST_BEGIN_STMT \
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assert_suggested_for (SELFTEST_LOCATION, CANDIDATE, TARGET); \
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SELFTEST_END_STMT
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/* Assert that CANDIDATE is not offered as a suggestion for TARGET. */
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static void
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assert_not_suggested_for (const location &loc, const char *candidate,
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const char *target)
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{
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auto_vec<const char *> candidates;
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candidates.safe_push (candidate);
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ASSERT_EQ_AT (loc, NULL, find_closest_string (target, &candidates));
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}
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/* Assert that CANDIDATE is not offered as a suggestion for TARGET. */
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#define ASSERT_NOT_SUGGESTED_FOR(CANDIDATE, TARGET) \
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SELFTEST_BEGIN_STMT \
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assert_not_suggested_for (SELFTEST_LOCATION, CANDIDATE, TARGET); \
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SELFTEST_END_STMT
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/* Verify that we offer varous suggestions that are meaningful,
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and that we don't offer various other ones that aren't (PR c/82967). */
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static void
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test_suggestions ()
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{
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/* Good suggestions. */
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ASSERT_SUGGESTED_FOR ("m_bar", "bar");
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// dist == 2, max_length == 5, min_length == 3
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ASSERT_SUGGESTED_FOR ("MACRO", "MACRAME");
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// dist == 3, max_length == 7, min_length == 5
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ASSERT_SUGGESTED_FOR ("gtk_widget_show_all", "GtkWidgetShowAll");
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// dist == 7, max_length == 16, min_length = 19
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ASSERT_SUGGESTED_FOR ("ab", "ac");
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// dist == 1, max_length == min_length = 2
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ASSERT_SUGGESTED_FOR ("ab", "a");
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// dist == 1, max_length == 2, min_length = 1
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/* Bad suggestions. */
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ASSERT_NOT_SUGGESTED_FOR ("a", "b");
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// dist == 1, max_length == min_length = 1
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ASSERT_NOT_SUGGESTED_FOR ("sqrt", "assert");
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// dist == 3, max_length 6, min_length == 4
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ASSERT_NOT_SUGGESTED_FOR ("INT8_MAX", "PATH_MAX");
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// dist == 3, max_length == min_length == 8
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ASSERT_NOT_SUGGESTED_FOR ("nice", "time");
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ASSERT_NOT_SUGGESTED_FOR ("nanl", "name");
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// dist == 2, max_length == min_length == 4
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ASSERT_NOT_SUGGESTED_FOR ("carg", "bar");
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ASSERT_NOT_SUGGESTED_FOR ("char", "bar");
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// dist == 2, max_length == 4, min_length == 3
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ASSERT_NOT_SUGGESTED_FOR ("-optimize", "fsanitize");
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// dist == 5, max_length == min_length == 9
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ASSERT_NOT_SUGGESTED_FOR ("__DATE__", "__i386__");
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// dist == 4, max_length == min_length == 8
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ASSERT_NOT_SUGGESTED_FOR ("start_input_device", "InputDevice");
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// dist == 9, max_length == 18, min_length == 11
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}
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/* Verify that find_closest_string is sane. */
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static void
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test_find_closest_string ()
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{
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auto_vec<const char *> candidates;
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/* Verify that it can handle an empty vec. */
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ASSERT_EQ (NULL, find_closest_string ("", &candidates));
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/* Verify that it works sanely for non-empty vecs. */
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candidates.safe_push ("apple");
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candidates.safe_push ("banana");
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candidates.safe_push ("cherry");
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ASSERT_STREQ ("apple", find_closest_string ("app", &candidates));
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ASSERT_STREQ ("banana", find_closest_string ("banyan", &candidates));
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ASSERT_STREQ ("cherry", find_closest_string ("berry", &candidates));
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ASSERT_EQ (NULL, find_closest_string ("not like the others", &candidates));
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/* The order of the vec can matter, but it should not matter for these
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inputs. */
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candidates.truncate (0);
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candidates.safe_push ("cherry");
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candidates.safe_push ("banana");
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candidates.safe_push ("apple");
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ASSERT_STREQ ("apple", find_closest_string ("app", &candidates));
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ASSERT_STREQ ("banana", find_closest_string ("banyan", &candidates));
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ASSERT_STREQ ("cherry", find_closest_string ("berry", &candidates));
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ASSERT_EQ (NULL, find_closest_string ("not like the others", &candidates));
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/* If the goal string somehow makes it into the candidate list, offering
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it as a suggestion will be nonsensical. Verify that we don't offer such
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suggestions. */
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ASSERT_EQ (NULL, find_closest_string ("banana", &candidates));
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/* Example from PR 69968 where transposition helps. */
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candidates.truncate (0);
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candidates.safe_push("coordx");
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candidates.safe_push("coordy");
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candidates.safe_push("coordz");
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candidates.safe_push("coordx1");
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candidates.safe_push("coordy1");
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candidates.safe_push("coordz1");
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ASSERT_STREQ ("coordz1", find_closest_string ("coorzd1", &candidates));
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}
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/* Test data for test_metric_conditions. */
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static const char * const test_data[] = {
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"",
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"foo",
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"food",
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"boo",
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"1234567890123456789012345678901234567890123456789012345678901234567890"
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};
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/* Verify that get_edit_distance appears to be a sane distance function,
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i.e. the conditions for being a metric. This is done directly for a
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small set of examples, using test_data above. This is O(N^3) in the size
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of the array, due to the test for the triangle inequality, so we keep the
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array small. */
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static void
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test_metric_conditions ()
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{
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const int num_test_cases = sizeof (test_data) / sizeof (test_data[0]);
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for (int i = 0; i < num_test_cases; i++)
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{
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for (int j = 0; j < num_test_cases; j++)
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{
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edit_distance_t dist_ij
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= get_edit_distance (test_data[i], test_data[j]);
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/* Identity of indiscernibles: d(i, j) > 0 iff i == j. */
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if (i == j)
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ASSERT_EQ (dist_ij, 0);
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else
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ASSERT_TRUE (dist_ij > 0);
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/* Symmetry: d(i, j) == d(j, i). */
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edit_distance_t dist_ji
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= get_edit_distance (test_data[j], test_data[i]);
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ASSERT_EQ (dist_ij, dist_ji);
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/* Triangle inequality. */
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for (int k = 0; k < num_test_cases; k++)
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{
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edit_distance_t dist_ik
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= get_edit_distance (test_data[i], test_data[k]);
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|
edit_distance_t dist_jk
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|
= get_edit_distance (test_data[j], test_data[k]);
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ASSERT_TRUE (dist_ik <= dist_ij + dist_jk);
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|
}
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|
}
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|
}
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|
}
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|
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/* Run all of the selftests within this file. */
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|
|
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void
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|
spellcheck_c_tests ()
|
|
{
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test_edit_distances ();
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|
test_get_edit_distance_cutoff ();
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|
test_suggestions ();
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|
test_find_closest_string ();
|
|
test_metric_conditions ();
|
|
}
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|
|
|
} // namespace selftest
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|
|
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#endif /* #if CHECKING_P */
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