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|
{-# LANGUAGE DataKinds #-}
{-# LANGUAGE GADTs #-}
{-# LANGUAGE KindSignatures #-}
{-# LANGUAGE PolyKinds #-}
{-# LANGUAGE TemplateHaskell #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE TypeOperators #-}
module TH_RichKinds2 where
import Data.Char
import Data.List
import Language.Haskell.TH
$(return [OpenTypeFamilyD (TypeFamilyHead
(mkName "Map") [KindedTV (mkName "f")
(AppT (AppT ArrowT (VarT (mkName "k1")))
(VarT (mkName "k2"))),
KindedTV (mkName "l")
(AppT ListT
(VarT (mkName "k1")))]
(KindSig (AppT ListT (VarT (mkName "k2")))) Nothing)])
$( let fixKs :: String -> String -- need to remove TH renaming index from k variables
fixKs s =
case (elemIndex 'k' s) of
Nothing -> s
Just i ->
if i == (length s) || (s !! (i+1) /= '_') then s else
let (prefix, suffix) = splitAt (i+2) s -- the +2 for the "k_"
(index, rest) = span isDigit suffix in
if length index == 0 then s else
prefix ++ "0" ++ (fixKs rest)
in
do decls <- [d| data SMaybe :: (k -> *) -> (Maybe k) -> * where
SNothing :: SMaybe s 'Nothing
SJust :: s a -> SMaybe s ('Just a)
type instance Map f '[] = '[]
type instance Map f (h ': t) = ((f h) ': (Map f t))
|]
reportWarning (fixKs (pprint decls))
return decls )
data SBool :: Bool -> * where
SFalse :: SBool 'False
STrue :: SBool 'True
mbool :: SMaybe SBool ('Just 'False)
mbool = SJust SFalse
|
