multi_bimap

Many-to-many bidirectional map in Rust.

This crate provides a MultiBimap struct, a bidirectional multimap that is implemented as two antiparallel multimaps that are kept in sync.

This structure is also known under many other names: bi-multimap, multi-bimap, or sometimes even just bimap; in set theory, it's simply called a relation; in graph theory, it's the same as a bipartite graph.

Usage

Adding dependency

First, add multi_bimap as a dependency to your Cargo.toml:

[dependencies]
multi_bimap = "0.2.0"

Example

A MultiBimap keeps two antiparallel multimaps in sync; each side may map a key to multiple values. You can look up associations in either direction.

use multi_bimap::MultiBimap;
use std::collections::{HashMap, HashSet};

let mut m: MultiBimap<HashMap<&str, HashSet<i32>>, HashMap<i32, HashSet<&str>>> = MultiBimap::new();

m.insert("a", 1);
m.insert("a", 2);
m.insert("b", 1);

// Look up all right values for a left key.
assert_eq!(m.get_by_left("a"), Some(&HashSet::from([1, 2])));

// Look up all left values for a right key.
assert_eq!(m.get_by_right(&1), Some(&HashSet::from(["a", "b"])));

// Remove one association; empty keys are dropped automatically.
assert_eq!(m.remove(&"a", &1), Some(("a", 1)));