ZeggenLaten.hs

{-# language 
  GADTSyntax,
  FlexibleInstances
#-}

import Prelude hiding (String)
import qualified Prelude

main :: IO ()
main = print sample

-- \f -> f (\FormalParameter -> Haar (Iets FormalParameter)) (\FormalParameter -> Willen (Laten (Zeggen FormalParameter)))

sample :: Tup
sample = want (let_ (say something) her)

type String = Star -> Star
type Tup = (String -> String -> Prelude.String) -> Prelude.String

her :: String
her = Haar

something :: String
something = Iets

say :: String -> Tup
say = \x f -> f x Zeggen

want :: Tup -> Tup
want = \q f -> q (\y z -> f y (Willen . z))

let_ :: Tup -> String -> Tup
let_ = \q x f -> q (\z w -> f (x . z) (Laten . w))

data Star where
  Haar :: Star -> Star
  Iets :: Star -> Star
  Zeggen :: Star -> Star
  Laten :: Star -> Star
  Willen :: Star -> Star
  FormalParameter :: Star
  deriving Show

instance Show String where
  show s = "\\FormalParameter -> " ++ show (s FormalParameter)

instance Show ((String -> String -> Prelude.String) -> Prelude.String) where
  show tup =
    tup
      (\a b ->
        "\\f -> f (" ++ show a ++ ") ("
        ++
        show b ++ ")"
      )