TypeFamilies - class Key k
| Run Settings | |
|---|---|
| Language | Haskell |
| Language Version | |
| Run Command |
| Snippet Metadata | |
|---|---|
| Owner | homam |
| Created | |
| Modified | |
| Visibility | Public |
{-# LANGUAGE TypeFamilies #-}
class Key k where
data Map k :: * -> *
empty :: Map k v
lookup :: k -> Map k v -> Maybe v
instance Key Bool where
data Map Bool v = MapBool (Maybe v) (Maybe v)
empty = MapBool Nothing Nothing
lookup True (MapBool _ t) = t
lookup False (MapBool f _) = f
main = putStrLn "Hello World!"
| Editor Settings | |
|---|---|
| Theme | |
| Key bindings | |
| Full width | |
| Lines |