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{-# LANGUAGE DataKinds #-}
{-# LANGUAGE EmptyCase #-}
{-# LANGUAGE GADTs #-}
{-# LANGUAGE PolyKinds #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE StandaloneDeriving #-}
{-# LANGUAGE StandaloneKindSignatures #-}
{-# LANGUAGE TypeAbstractions #-}
{-# LANGUAGE TypeApplications #-}
{-# LANGUAGE TypeOperators #-}
{-# LANGUAGE PartialTypeSignatures #-}
{-# OPTIONS -Wno-partial-type-signatures #-}
-- The reason why this is a separate module with "little" in it:
{-# LANGUAGE AllowAmbiguousTypes #-}
module AST.Weaken (module AST.Weaken, Append) where
import Data.Bifunctor (first)
import Data.Functor.Const
import Data.Kind (Type)
import Data
import Lemmas
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)
splitIdx :: forall env2 env1 t f. SList f env1 -> Idx (Append env1 env2) t -> Either (Idx env1 t) (Idx env2 t)
splitIdx SNil i = Right i
splitIdx (SCons _ _) IZ = Left IZ
splitIdx (SCons _ l) (IS i) = first IS (splitIdx l i)
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
WPick :: forall t pre env env'. SList (Const ()) pre -> env :> env'
-> Append pre (t : env) :> t : Append pre env'
WSwap :: forall env as bs. SList (Const ()) as -> SList (Const ()) bs
-> Append as (Append bs env) :> Append bs (Append as env)
deriving instance Show (env :> env')
infix 4 :>
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
WPick SNil w @> i = WCopy w @> i
WPick (_ `SCons` _) _ @> IZ = IS IZ
WPick @t (_ `SCons` pre) w @> IS i = WCopy WSink .> WPick @t pre w @> i
WSwap @env (as :: SList _ as) (bs :: SList _ bs) @> i =
case splitIdx @(Append bs env) as i of
Left i' -> skipOver bs (stack @env i' as)
Right i' -> case splitIdx @env bs i' of
Left j -> stack @(Append as env) j bs
Right j -> skipOver bs (skipOver as j)
where
skipOver :: SList (Const ()) as' -> Idx bs' t -> Idx (Append as' bs') t
skipOver SNil j = j
skipOver (_ `SCons` bs') j = IS (skipOver bs' j)
stack :: forall env' as' t. Idx as' t -> SList (Const ()) as' -> Idx (Append as' env') t
stack IZ (_ `SCons` _) = IZ
stack (IS j) (_ `SCons` as') = IS (stack @env' j as')
infixr 3 .>
(.>) :: env2 :> env3 -> env1 :> env2 -> env1 :> env3
(.>) = flip WThen
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)
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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