bidict

A bijective dictionary. Each key corresponds to one value, and each value corresponds to one key. To achieve this, a Bidict stores two one-way mappings: Bidict(a2b: Dict(a, b), b2a: Dict(b, a)). All functions properly update both forward and reverse mappings.

API is mostly the same as gleam/dict, though with a few differences:

• delete -> delete_a, delete_b
• drop -> drop_a, drop_b
• get -> get_a, get_b
• has_key -> has_a, has_b
• new map_keys
• new map

Install

gleam add bidict

Usage

import bidict

pub fn main() {
  let elements: Bidict(String, String) =
    [
      #("Hydrogen", "H"),
      #("Carbon", "C"),
      #("Bromine", "Br"),
      #("Neodymium", "Nd"),
    ]
    |> bidict.from_list

  let assert Ok("Br") = bidict.get_a(elements, "Bromine")
  let assert Error(Nil) = bidict.get_a(elements, "Oxygen")

  let assert Ok("Carbon") = bidict.get_b(elements, "C")
  let assert Error(Nil) = bidict.get_b(elements, "Al")

  let assert True = bidict.has_a(elements, "Hydrogen")
  let assert False = bidict.has_b(elements, "He")

  let assert False =
    elements
    |> bidict.delete_a("Neodymium")
    |> bidict.has_b("Ne")

  let assert 3 =
    elements
    |> bidict.insert("Bromine", "Nd")
    |> bidict.size
}

Further documentation can be found at https://hexdocs.pm/bidict.

Implementations in Other Languages

• Rust - bimap
• Python - bidict
• Haskell - bimap