robertjlooby/elm-generic-dict

A dictionary and set implementation for Elm that accepts a user-provided comparer

GenericDict / GenericSet

The core Dict/Set implementations only allows keys of comparable type. This implementation builds off the core implementation but allows the user to provide their own comparer function for ordering the keys. This allows both the storage of arbitrary key types as well as changing the ordering of the elements (which affects how they will be returned from toList for example).

The api is essentially the same as the core Dict/Set except that the "builder" functions (empty, singleton , fromList) take a comparer of type (key -> key -> Order) as their first argument.

import GenericDict exposing (GenericDict)
import String exposing (toLower)

type alias Person =
    { id : Int
    , name : String
    }

dict1 : GenericDict Person Int
dict1 =
    GenericDict.fromList
        (\person1 person2 -> compare person1.id person2.id)
        [ ( { id = 1, name = "Noah" }, 1 ), ( { id = 2, name = "Evan" }, 2 ) ]
-- Dict.fromList [({ id = 1, name = "Noah" }, 1), ({ id = 2, name = "Evan" }, 2)]

dict2 : GenericDict String Int
dict2 =
    GenericDict.fromList
        (\str1 str2 -> compare (toLower str1) (toLower str2))
        [ ( "FIRST", 1 ), ( "SECOND", 2 ), ( "First", 3 ) ]
-- Dict.fromList [("FIRST", 3), ("SECOND", 2)]

f : Maybe Int
f = GenericDict.get "FiRsT" dict2
-- Just 3

This builds off of the core Dict implementation by Evan Czaplicki as well as the similar elm-all-dict by Noah Hall.

elm-generic-dict's Issues

Sample codes in README cannot be compiled

I found that sample codes in README.md produces compile errors.
There are two reasons why it fails to be compiled.
First, it uses ' in variable name, which was unsupported after Elm 0.18.
Next, second argument of the fromList is not a list of Tuple.

P.S. I feel that this module has the best function design of all the similar libraries!