Union Types
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{-# LANGUAGE GADTs #-}
data Func where
Func :: (A -> B) -> Func
data A = AInt Int | AString String deriving (Show, Read)
data B = BInt Int | BString String deriving (Show, Read)
f1 :: Func
f1 = Func $ \ (AInt i) -> BInt $ i * 2
f2 :: Func
f2 = Func $ \ (AString i) -> BString $ i ++ "!"
getF :: String -> Func
getF "f1" = f1
getF "f2" = f2
exec :: Func -> A -> B
exec (Func f) = f
main = print $ exec (getF "f1") (read "AInt 4")
Haskell
INFO