55 lines
1.6 KiB
Rust
55 lines
1.6 KiB
Rust
use std::collections::HashMap;
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use std::hash::Hash;
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use super::DiffableStrRef;
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// quick and dirty way to get an upper sequence ratio.
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pub fn upper_seq_ratio<T: PartialEq>(seq1: &[T], seq2: &[T]) -> f32 {
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let n = seq1.len() + seq2.len();
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if n == 0 {
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1.0
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} else {
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2.0 * seq1.len().min(seq2.len()) as f32 / n as f32
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}
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}
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/// Internal utility to calculate an upper bound for a ratio for
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/// [`get_close_matches`]. This is based on Python's difflib approach
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/// of considering the two sets to be multisets.
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///
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/// It counts the number of matches without regard to order, which is an
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/// obvious upper bound.
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pub struct QuickSeqRatio<'a, T: DiffableStrRef + ?Sized>(HashMap<&'a T, i32>);
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impl<'a, T: DiffableStrRef + Hash + Eq + ?Sized> QuickSeqRatio<'a, T> {
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pub fn new(seq: &[&'a T]) -> QuickSeqRatio<'a, T> {
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let mut counts = HashMap::new();
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for &word in seq {
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*counts.entry(word).or_insert(0) += 1;
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}
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QuickSeqRatio(counts)
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}
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pub fn calc(&self, seq: &[&T]) -> f32 {
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let n = self.0.len() + seq.len();
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if n == 0 {
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return 1.0;
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}
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let mut available = HashMap::new();
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let mut matches = 0;
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for &word in seq {
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let x = if let Some(count) = available.get(&word) {
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*count
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} else {
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self.0.get(&word).copied().unwrap_or(0)
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};
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available.insert(word, x - 1);
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if x > 0 {
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matches += 1;
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}
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}
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2.0 * matches as f32 / n as f32
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}
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}
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