24 lines
638 B
Rust
24 lines
638 B
Rust
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use std::collections::HashMap;
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use std::hash::Hash;
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use std::cmp::Eq;
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#[derive(Default, Debug)]
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pub struct StateStack<'a, T: 'a, V: 'a> where T: Hash + Eq {
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parent: Option<&'a StateStack<'a, T, V>>,
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values: HashMap<T, V>
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}
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impl<'a, T, V> StateStack<'a, T, V> where T: Hash + Eq {
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pub fn insert(&mut self, key: T, value: V) where T: Hash + Eq {
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self.values.insert(key, value);
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}
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pub fn lookup(&self, key: &T) -> Option<&V> where T: Hash + Eq {
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match (self.values.get(key), self.parent) {
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(None, None) => None,
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(None, Some(parent)) => parent.lookup(key),
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(Some(value), _) => Some(value),
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}
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}
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}
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