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{-# LANGUAGE DataKinds #-}
{-# LANGUAGE EmptyCase #-}
{-# LANGUAGE GADTs #-}
{-# LANGUAGE PolyKinds #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE StandaloneDeriving #-}
{-# LANGUAGE StandaloneKindSignatures #-}
{-# LANGUAGE TypeApplications #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE TypeOperators #-}
-- The reason why this is a separate module with "little" in it:
{-# LANGUAGE AllowAmbiguousTypes #-}
module AST.Weaken where
import Data.Functor.Const
import Data.Kind (Type)
import Data
type Idx :: [k] -> k -> Type
data Idx env t where
IZ :: Idx (t : env) t
IS :: Idx env t -> Idx (a : env) t
deriving instance Show (Idx env t)
data env :> env' where
WId :: env :> env
WSink :: forall t env. env :> (t : env)
WCopy :: env :> env' -> (t : env) :> (t : env')
WPop :: (t : env) :> env' -> env :> env'
WThen :: env1 :> env2 -> env2 :> env3 -> env1 :> env3
WClosed :: SList (Const ()) env -> '[] :> env
WIdx :: Idx env t -> (t : env) :> env
deriving instance Show (env :> env')
infixr 2 @>
(@>) :: env :> env' -> Idx env t -> Idx env' t
WId @> i = i
WSink @> i = IS i
WCopy _ @> IZ = IZ
WCopy w @> (IS i) = IS (w @> i)
WPop w @> i = w @> IS i
WThen w1 w2 @> i = w2 @> w1 @> i
WClosed _ @> i = case i of {}
WIdx j @> IZ = j
WIdx _ @> IS i = i
infixr 3 .>
(.>) :: env2 :> env3 -> env1 :> env2 -> env1 :> env3
(.>) = flip WThen
type family Append a b where
Append '[] l = l
Append (x : xs) l = x : Append xs l
class KnownListSpine list where knownListSpine :: SList (Const ()) list
instance KnownListSpine '[] where knownListSpine = SNil
instance KnownListSpine list => KnownListSpine (t : list) where knownListSpine = SCons (Const ()) knownListSpine
wSinks' :: forall list env. KnownListSpine list => env :> Append list env
wSinks' = wSinks (knownListSpine :: SList (Const ()) list)
wSinks :: forall env bs f. SList f bs -> env :> Append bs env
wSinks SNil = WId
wSinks (SCons _ spine) = WSink .> wSinks spine
wCopies :: SList f bs -> env1 :> env2 -> Append bs env1 :> Append bs env2
wCopies SNil w = w
wCopies (SCons _ spine) w = WCopy (wCopies spine w)
wStack :: forall env b1 b2. b1 :> b2 -> Append b1 env :> Append b2 env
wStack WId = WId
wStack WSink = WSink
wStack (WCopy w) = WCopy (wStack @env w)
wStack (WPop w) = WPop (wStack @env w)
wStack (WThen w1 w2) = WThen (wStack @env w1) (wStack @env w2)
wStack (WClosed s) = wSinks s
wStack (WIdx i) = WIdx (goIdx i)
where
goIdx :: Idx b t -> Idx (Append b env) t
goIdx IZ = IZ
goIdx (IS i') = IS (goIdx i')
wRaiseAbove :: SList f env1 -> SList g env -> env1 :> Append env1 env
wRaiseAbove SNil env = WClosed (slistMap (\_ -> Const ()) env)
wRaiseAbove (SCons _ s) env = WCopy (wRaiseAbove s env)
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