1 //! Levenshtein distances.
3 //! The [Levenshtein distance] is a metric for measuring the difference between two strings.
5 //! [Levenshtein distance]: https://en.wikipedia.org/wiki/Levenshtein_distance
7 use crate::symbol::Symbol;
13 /// Finds the Levenshtein distance between two strings.
15 /// Returns None if the distance exceeds the limit.
16 pub fn lev_distance(a: &str, b: &str, limit: usize) -> Option<usize> {
17 let n = a.chars().count();
18 let m = b.chars().count();
19 let min_dist = if n < m { m - n } else { n - m };
25 return (min_dist <= limit).then_some(min_dist);
28 let mut dcol: Vec<_> = (0..=m).collect();
30 for (i, sc) in a.chars().enumerate() {
32 dcol[0] = current + 1;
34 for (j, tc) in b.chars().enumerate() {
35 let next = dcol[j + 1];
37 dcol[j + 1] = current;
39 dcol[j + 1] = cmp::min(current, next);
40 dcol[j + 1] = cmp::min(dcol[j + 1], dcol[j]) + 1;
46 (dcol[m] <= limit).then_some(dcol[m])
49 /// Finds the best match for a given word in the given iterator.
51 /// As a loose rule to avoid the obviously incorrect suggestions, it takes
52 /// an optional limit for the maximum allowable edit distance, which defaults
53 /// to one-third of the given word.
55 /// Besides Levenshtein, we use case insensitive comparison to improve accuracy
56 /// on an edge case with a lower(upper)case letters mismatch.
58 pub fn find_best_match_for_name(
59 candidates: &[Symbol],
63 let lookup = lookup.as_str();
64 let lookup_uppercase = lookup.to_uppercase();
66 // Priority of matches:
67 // 1. Exact case insensitive match
68 // 2. Levenshtein distance match
69 // 3. Sorted word match
70 if let Some(c) = candidates.iter().find(|c| c.as_str().to_uppercase() == lookup_uppercase) {
74 let mut dist = dist.unwrap_or_else(|| cmp::max(lookup.len(), 3) / 3);
77 match lev_distance(lookup, c.as_str(), dist) {
78 Some(0) => return Some(*c),
90 find_match_by_sorted_words(candidates, lookup)
93 fn find_match_by_sorted_words(iter_names: &[Symbol], lookup: &str) -> Option<Symbol> {
94 iter_names.iter().fold(None, |result, candidate| {
95 if sort_by_words(candidate.as_str()) == sort_by_words(lookup) {
103 fn sort_by_words(name: &str) -> String {
104 let mut split_words: Vec<&str> = name.split('_').collect();
105 // We are sorting primitive &strs and can use unstable sort here.
106 split_words.sort_unstable();
107 split_words.join("_")