9dcc185264
This traits augments HashMap so they have a `get_or_default` method that can be used to avoid boilerplate around usage of `entry.or_default`.
20 lines
487 B
Rust
20 lines
487 B
Rust
use std::collections::HashMap;
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use std::hash::Hash;
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pub trait MapWithDefault<K, V: Default> {
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fn get_or_default(&mut self, k: K) -> &mut V;
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}
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impl<K: Eq + Hash, V: Default> MapWithDefault<K, V> for HashMap<K, V> {
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fn get_or_default(&mut self, k: K) -> &mut V {
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self.entry(k).or_insert_with(|| V::default())
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}
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}
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#[test]
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fn test_default() {
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let mut hash_map = HashMap::new();
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hash_map.insert(42, "hello");
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assert_eq!(*hash_map.get_or_default(43), "");
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}
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