pe (TyF s d) = "(mkFunTy (" ++ ppType s ++ ") (" ++ ppType d ++ "))"
ppT
ppType (TyF s d) = "(mkFunTy (" ++ ppType s ++ ") (" ++ ppType d ++ "))"
ppType (TyF s d) = "(mkFunTy (" ++ ppType s ++ ") (" ++ ppType d ++ "))"