Code: #[derive(Eq, PartialEq, Hash)] enum Key { String(String), Bytes(Vec<u8>), } enum KeyRef<'a> { String(&'a str), Bytes(&'a [u8]), } fn query(map: &HashMap<Key, u32>, key: KeyRef) -> Option<u32> { // how to do it without allocating? } I tried various approaches, the only o…

You can define a trait AsKeyRef, and then implement Borrow<dyn AsKeyRef> for Key: pub trait AsKeyRef { fn as_key_ref(&self)->KeyRef<'_>; } impl<'a> PartialEq for dyn AsKeyRef+'a { fn eq(&self, other:&Self)->bool { self.as_key_ref() == other.as_key_ref() } } impl<'a> Eq for dyn AsKeyRef+'…

Stuck with querying a hashmap

mbrubeck August 31, 2020, 4:46am 4

Another solution is to use the indexmap crate, and impl Equivalent<Key> for KeyRef.

1 Like

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Stuck with querying a hashmap

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