95 lines
2.3 KiB
Rust
95 lines
2.3 KiB
Rust
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use std::collections::HashMap;
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use std::collections::HashSet;
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use std::collections::hash_map::Iter;
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use std::collections::hash_map::Keys;
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use std::collections::hash_map::RandomState;
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use std::hash::BuildHasher;
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use std::hash::Hash;
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type Count = i32;
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pub enum Net {
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PresentToAbsent,
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AbsentToAbsent,
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AbsentToPresent,
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PresentToPresent,
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}
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// Allows negative counts - a "delta"
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pub struct HashBag<V, S = RandomState> {
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counts: HashMap<V, Count, S>,
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}
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impl<V,S> HashBag<V,S>
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where V: Eq + Hash, S: BuildHasher + Default
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{
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pub fn new() -> HashBag<V,S> {
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HashBag {
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counts: HashMap::with_hasher(Default::default()),
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}
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}
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pub fn change(&mut self, key: V, delta: Count) -> Net { self._change(key, delta, false) }
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pub fn change_clamped(&mut self, key: V, delta: Count) -> Net { self._change(key, delta, true) }
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pub fn _change(&mut self, key: V, delta: Count, clamp: bool) -> Net {
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let old_count = self[&key];
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let mut new_count = old_count + delta;
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if clamp { new_count = new_count.max(0) }
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if new_count == 0 {
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self.counts.remove(&key);
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if old_count == 0 { Net::AbsentToAbsent } else { Net::PresentToAbsent }
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} else {
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self.counts.insert(key, new_count);
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if old_count == 0 { Net::AbsentToPresent } else { Net::PresentToPresent }
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}
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}
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pub fn clear(&mut self) {
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self.counts.clear();
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}
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pub fn contains_key(&self, key: &V) -> bool {
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self.counts.contains_key(key)
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}
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pub fn is_empty(&self) -> bool {
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self.counts.is_empty()
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}
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pub fn len(&self) -> usize {
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self.counts.len()
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}
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pub fn keys(&self) -> Keys<V, Count> {
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self.counts.keys()
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}
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pub fn iter(&self) -> Iter<V, Count> {
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self.counts.iter()
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}
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}
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impl<V,S> std::convert::From<HashSet<V, S>> for HashBag<V,S>
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where V: Eq + Hash + Clone, S: BuildHasher + Default
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{
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fn from(xs: HashSet<V,S>) -> Self {
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let mut cs = HashMap::with_hasher(Default::default());
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for k in xs.iter() {
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cs.insert(k.clone(), 1);
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}
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HashBag {
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counts: cs
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}
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}
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}
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impl<V,S> std::ops::Index<&V> for HashBag<V,S>
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where V: Eq + Hash, S: BuildHasher
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{
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type Output = Count;
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fn index(&self, i: &V) -> &Count {
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self.counts.get(i).unwrap_or(&0)
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}
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}
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