elm-all-dict

This library provides two Dict implementations. Firstly, it provides AllDict, a dictionary which you may pass a hashing function in order to allow all types to be stored as keys.

Secondly, it provides EveryDict, a dictionary which uses toString as a hashing function.

This is a dictionary based off of core's Dict implementation, except it can support any type, rather than just comparables. A function must be given which will hash the key into a comparable.

module Main where

import Graphics.Element exposing (show)
import AllDict exposing (AllDict)
import EveryDict exposing (EveryDict)

type Action = Run | Hide | StandStill

ord : Action -> Int
ord action =
    case action of
        Run -> 0
        Hide -> 1
        StandStill -> 2

actionDict : AllDict Action String Int
actionDict =
    AllDict.fromList
        ord
        [ (Run, "Run away!")
        , (Hide, "Coward!")
        , (StandStill, "Err...")]

actionDict' : EveryDict Action String
actionDict' =
    EveryDict.fromList
        [ (Run, "Run away!")
        , (Hide, "Coward!")
        , (StandStill, "Err...")]

main = show <| EveryDict.toList actionDict'

EveryDict

EveryDict is special. It uses a custom implementation of toString in order to allow functions to be used as keys. The current implementation of toString doesn't actually work properly when functions are defined in the format

var f = function() ...

This is down to the fact toString uses the .name of the functions - this is obviously not defined when using the variable binding to anonymous functions that is common in JS.

I'm not sure if I can recommend this for use in production or not. It seems pretty breakable and dodgy, but maybe it's not.