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{-# LANGUAGE DataKinds #-}
{-# LANGUAGE GADTs #-}
{-# LANGUAGE KindSignatures #-}
{-# LANGUAGE StandaloneDeriving #-}
{-# LANGUAGE TypeOperators #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE UndecidableInstances #-}
module AST.Accum where
import AST.Types
import Data
data AcPrj
= APHere
| APFst AcPrj
| APSnd AcPrj
| APLeft AcPrj
| APRight AcPrj
| APJust AcPrj
| APArrIdx AcPrj
| APArrSlice Nat
-- | @b@ is a small part of @a@, indicated by the projection.
data SAcPrj (p :: AcPrj) (a :: Ty) (b :: Ty) where
SAPHere :: SAcPrj APHere a a
SAPFst :: SAcPrj p a b -> SAcPrj (APFst p) (TPair t a) b
SAPSnd :: SAcPrj p a b -> SAcPrj (APSnd p) (TPair a t) b
SAPLeft :: SAcPrj p a b -> SAcPrj (APLeft p) (TEither t a) b
SAPRight :: SAcPrj p a b -> SAcPrj (APRight p) (TEither t a) b
SAPJust :: SAcPrj p a b -> SAcPrj (APJust p) (TMaybe t) b
SAPArrIdx :: SAcPrj p a b -> SNat n -> SAcPrj (APArrIdx p) (TArr n t) b
SAPArrSlice :: SNat m -> SAcPrj (APArrSlice m) (TArr n t) (TArr (n - m) t)
deriving instance Show (SAcPrj p a b)
type family AcIdx p t where
AcIdx APHere t = TNil
AcIdx (APFst p) (TPair a b) = AcIdx p a
AcIdx (APSnd p) (TPair a b) = AcIdx p b
AcIdx (APLeft p) (TEither a b) = AcIdx p a
AcIdx (APRight p) (TEither a b) = AcIdx p b
AcIdx (APJust p) (TMaybe a) = AcIdx p a
AcIdx (APArrIdx p) (TArr n a) = TPair (Tup (Replicate n TIx)) (AcIdx p a)
AcIdx (APArrSlice m) (TArr n a) = Tup (Replicate m TIx)
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