vendor/similar/src/text/utils.rs

   1 use std::collections::HashMap;
   2 use std::hash::Hash;
   3
   4 use super::DiffableStrRef;
   5
   6 // quick and dirty way to get an upper sequence ratio.
   7 pub fn upper_seq_ratio<T: PartialEq>(seq1: &[T], seq2: &[T]) -> f32 {
   8     let n = seq1.len() + seq2.len();
   9     if n == 0 {
  10         1.0
  11     } else {
  12         2.0 * seq1.len().min(seq2.len()) as f32 / n as f32
  13     }
  14 }
  15
  16 /// Internal utility to calculate an upper bound for a ratio for
  17 /// [`get_close_matches`].  This is based on Python's difflib approach
  18 /// of considering the two sets to be multisets.
  19 ///
  20 /// It counts the number of matches without regard to order, which is an
  21 /// obvious upper bound.
  22 pub struct QuickSeqRatio<'a, T: DiffableStrRef + ?Sized>(HashMap<&'a T, i32>);
  23
  24 impl<'a, T: DiffableStrRef + Hash + Eq + ?Sized> QuickSeqRatio<'a, T> {
  25     pub fn new(seq: &[&'a T]) -> QuickSeqRatio<'a, T> {
  26         let mut counts = HashMap::new();
  27         for &word in seq {
  28             *counts.entry(word).or_insert(0) += 1;
  29         }
  30         QuickSeqRatio(counts)
  31     }
  32
  33     pub fn calc(&self, seq: &[&T]) -> f32 {
  34         let n = self.0.len() + seq.len();
  35         if n == 0 {
  36             return 1.0;
  37         }
  38
  39         let mut available = HashMap::new();
  40         let mut matches = 0;
  41         for &word in seq {
  42             let x = if let Some(count) = available.get(&word) {
  43                 *count
  44             } else {
  45                 self.0.get(&word).copied().unwrap_or(0)
  46             };
  47             available.insert(word, x - 1);
  48             if x > 0 {
  49                 matches += 1;
  50             }
  51         }
  52
  53         2.0 * matches as f32 / n as f32
  54     }
  55 }