elm-default-dict

Use default dictionaries in Elm!

-- create a default dictionary with the value 0
ages : DefaultDict String Int
ages =
    DefaultDict.empty 0

-- equal to 5
mikesAge =
    DefaultDict.insert "Mike" 5 ages
        |> DefaultDict.get "Mike"

-- equal to 0
someoneElse =
    DefaultDict.get "David" ages

everyonesAges : DefaultDict String Int
everyonesAges =
    DefaultDict.fromList
        100
        [ ("Mike", 5)
        , ("David", 0)
        , ("Tommy", 19)]

-- equal to 100
leesAge =
    DefaultDict.get "Lee" everyonesAges

When should I use this?

Whenever you want a dictionary to have a default value. The implementation is roughly 70% identical to core's Dict, meaning that the API mirrors it exactly.

The increased size overhead is 4 * size of v. v is stored on each of the RBEmpty leafs.

Interesting notes

Due to the way that toString works internally, our DefaultDict can get pretty printing for free by using the same types used to implement Dict.