To make something the key of a HashMap, you need to satisfy 3 traits: Hash — How do you calculate a hash value for the type? PartialEq — How do you decide if two instances of a type are the same? Eq — Can you guarantee that the equality is reflexive, symmetric, and transitive? This … Read more
There are at least two reasons why this is disallowed: You would need to have two concurrent mutable references to map — one held by the iterator used in the for loop and one in the variable map to call map.remove. You have references to the key and the value within the map when trying … Read more
hellow has shown how to get working code, but I want to dive a bit more into why your code does not compile. The code you have proposed cannot be statically verified to be memory safe. It’s entirely possible that your recursive calls attempt to access the same index. Check out this simplified code for … Read more
Your usage of additionalProperties is correct and your model is correct. additionalProperties In Swagger/OpenAPI, hashmap keys are assumed to be strings, so the key type is not defined explicitly. additionalProperties define the type of hashmap values. So, this schema type: object additionalProperties: type: string defines a string-to-string map such as: { “en”: “English text”, “de”: … Read more
Indexing immutably and indexing mutably are provided by two different traits: Index and IndexMut, respectively. Currently, HashMap does not implement IndexMut, while Vec does. The commit that removed HashMap‘s IndexMut implementation states: This commit removes the IndexMut impls on HashMap and BTreeMap, in order to future-proof the API against the eventual inclusion of an IndexSet … Read more
There isn’t a map literal syntax in Rust. I don’t know the exact reason, but I expect that the fact that there are multiple data structures that act maplike (such as both BTreeMap and HashMap) would make it hard to pick one. Rust 1.56 Many collections now offer conversions from an array argument using From … Read more
This is certainly possible. The signature of get is fn get<Q: ?Sized>(&self, k: &Q) -> Option<&V> where K: Borrow<Q>, Q: Hash + Eq, The problem here is to implement a &Q type such that (A, B): Borrow<Q> Q implements Hash + Eq To satisfy condition (1), we need to think of how to write fn … Read more
The entry API is designed for this. In manual form, it might look like let values = match map.entry(key) { Entry::Occupied(o) => o.into_mut(), Entry::Vacant(v) => v.insert(default), }; One can use the briefer form via Entry::or_insert_with: let values = map.entry(key).or_insert_with(|| default); If default is already computed, or if it’s OK/cheap to compute even when it isn’t … Read more