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