2022-07-18 02:00:19 +00:00
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use std::collections::HashMap;
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use std::hash::Hash;
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2022-04-28 16:33:26 +00:00
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2022-07-18 02:00:19 +00:00
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pub struct LayeredEnv<K, V> {
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parent: Option<Box<LayeredEnv<K, V>>>,
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inner_map: HashMap<K, V>,
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}
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2022-04-28 16:33:26 +00:00
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2022-07-18 02:00:19 +00:00
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impl<K: Hash + Eq, V> LayeredEnv<K, V> {
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2022-07-18 02:13:09 +00:00
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pub fn new() -> Self {
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LayeredEnv {
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parent: None,
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inner_map: HashMap::new(),
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}
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}
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2022-07-18 02:00:19 +00:00
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pub fn insert(&mut self, key: K, value: V) {
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self.inner_map.insert(key, value);
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}
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pub fn push(self) -> LayeredEnv<K, V> {
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LayeredEnv {
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parent: Some(Box::new(self)),
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inner_map: HashMap::new(),
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}
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}
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pub fn pop(self) -> LayeredEnv<K, V> {
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*self.parent.unwrap()
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2022-04-28 16:33:26 +00:00
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}
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2022-07-18 02:00:19 +00:00
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pub fn lookup(&self, key: &K) -> Option<&V> {
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match self.inner_map.get(key) {
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Some(v) => Some(v),
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None => match self.parent.as_ref() {
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Some(p) => p.lookup(key),
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None => None,
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},
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}
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2022-04-28 16:33:26 +00:00
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}
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}
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