Option.hs

{-# LANGUAGE TypeFamilies, DataKinds, TypeOperators, FlexibleInstances #-}

import GHC.TypeLits

type family FuncType (as :: [*]) where
  FuncType '[] = IO ()
  FuncType (a ': as) = a -> FuncType as

data Name (s :: Symbol) = Name

data FullOption = FullOption {
  opt1 :: Int,
  opt2 :: String,
  opt3 :: [Int]
} deriving (Eq, Show)

class Hoge (s :: Symbol) where
  type Arg :: [*]
  hoge :: Name s -> FuncType Arg
  hogeFullOption :: Name s -> FullOption -> IO ()
  hogeFullOption _ opt = print opt

instance Hoge "this" where
  type Arg = [Int, Char]
  hoge _ n c = putStrLn $ "int: " ++ show n ++ " char: " ++ show c

this = hoge (Name :: Name "this")

main = do
  this 10 '#'