HashMap

In Rust it's using rpds::HashTrieMap. And in JavaScript, it's built on top of ternary-tree with some tricks for very small dicts.

Usage

{} is a macro, you can quickly write in pairs:

{}
  :a 1
  :b 2

internally it's turned into a native function calling arguments:

&{} :a 1 :b 2

let
    dict $ {}
      :a 1
      :b 2
  println $ to-pairs dict
  println $ map-kv dict $ fn (k v)
    [] k (inc v)