Hotel

Simple collection datastructure to associate data with unique keys.

Properties and Advantages

The key is of type usize, and can therefore cheaply be passed around in favour of the actual data.

The advantage is that keys can be cloned unbeatable cheaply and no hashing of keys has to ever take place. This also means no collisions can ever happen.

put, remove, get, take are all O(1) operations.

The Hotel is backed by a Vec and is very memory efficient. Thanks to this it's very much efficient to use on modern CPUs by virtue of inheriting the Vecs cache-friendliness.

Use cases

Here are examples

• Often used together with Maps in order to avoid hashing often and cloning keys.
• In some cases can be used as an high-performance HashMap replacement.
• Implementing graphs! Graphs can take many forms, in some way they can be found in almost every programm. Trees are simple, everything else is not so obvious to implement in rust, thanks to it's ownership rules. A Hotel is the perfect place to store ownership of the Nodes and manage edges as keys.

Example

here's a simple Graph. A -> B -> C

let mut nodes: Hotel<Node>,
let mut edges: Vec<(usize, usize)>

let key1 = nodes.put(Node::new(a));
let key2 = nodes.put(Node::new(b));
let key3 = nodes.put(Node::new(c));
edges.push( (key1, key2) );
edges.push( (key2, key3) );

HotelMap

Additionally, this crate contains the HotelMap datastructure. It's a shorthand for mapping keys to simple usize values, and being able to index with both. This can have the advantage of being able to use copyable and small usize, instead of carrying around complex and large keys all the time.