Prototype, extremely bad code implementation of CCHM Cubical Type Theory
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{-# LANGUAGE ViewPatterns #-}
{-# LANGUAGE DeriveAnyClass #-}
{-# LANGUAGE BlockArguments #-}
{-# LANGUAGE LambdaCase #-}
module Eval where
import Syntax
import qualified Data.Map.Strict as Map
import Data.Foldable
import Control.Exception
import Data.Typeable
import System.IO.Unsafe (unsafePerformIO)
import Data.IORef
import Systems
import Presyntax (Formula)
import qualified Presyntax as P
import Data.Maybe
import Debug.Trace
import GHC.Stack
iand :: Value -> Value -> Value
iand = \case
VI1 -> id
VI0 -> const VI0
x -> \case
VI0 -> VI0
VI1 -> x
y -> VIAnd x y
ior :: Value -> Value -> Value
ior = \case
VI0 -> id
VI1 -> const VI1
x -> \case
VI1 -> VI1
VI0 -> x
y -> VIOr x y
inot :: Value -> Value
inot VI1 = VI0
inot VI0 = VI1
inot (VIOr x y) = iand (inot x) (inot y)
inot (VIAnd x y) = ior (inot x) (inot y)
inot (VINot x) = x
inot x = VINot x
(@@) :: Value -> Value -> Value
VNe hd xs @@ vl = VNe hd (PApp vl:xs)
VLam _ _ k @@ vl = k vl
VEqGlued a b @@ vl = VEqGlued (a @@ vl) (b @@ vl)
VOfSub a phi u0 x @@ vl = x @@ vl
f @@ _ = error $ "can't apply argument to " ++ show f
proj1 :: Value -> Value
proj1 (VPair x _) = x
proj1 (VEqGlued x y) = VEqGlued (proj1 x) (proj1 y)
proj1 (VNe s xs) = VNe s (PProj1:xs)
proj1 (VOfSub (VSigma _ d _) phi u0 x) = VOfSub d phi (proj1 u0) (proj1 x)
proj1 x = error $ "can't proj1 " ++ show x
proj2 :: Value -> Value
proj2 (VPair _ y) = y
proj2 (VEqGlued x y) = VEqGlued (proj1 x) (proj1 y)
proj2 (VNe s xs) = VNe s (PProj2:xs)
proj2 (VOfSub (VSigma _ d r) phi u0 x) =
VOfSub (r (proj1 x)) phi (proj2 u0) (proj2 x)
proj2 x = error $ "can't proj2 " ++ show x
pathp :: Env -> Value -> Value -> Value -> Value -> Value -> Value
pathp env p x y f@(VLine _a _x _y e) i =
case reduceCube env i of
Just P.Bot -> VEqGlued (e i) x
Just P.Top -> VEqGlued (e i) y
_ -> e i
pathp env p x y (VEqGlued e e') i = VEqGlued (pathp env p x y e i) (pathp env p x y e' i)
pathp env p x y (VNe hd sp) i =
case reduceCube env i of
Just P.Bot -> VEqGlued (VNe hd (PPathP p x y i:sp)) x
Just P.Top -> VEqGlued (VNe hd (PPathP p x y i:sp)) y
_ -> VNe hd (PPathP p x y i:sp)
pathp env p x y (VOfSub _ _ _ v) i = pathp env p x y v i
comp :: Env -> Value -> Formula -> Value -> Value -> Value
comp env a@(VLam ivar VI fam) phi u a0 = go (fam undefined) phi u a0 where
i = VVar ivar
stuck :: Value
stuck = maybeAddEq $ VComp a (toValue phi) u a0
maybeAddEq :: Value -> Value
maybeAddEq =
if phi == P.Top
then flip VEqGlued (u @@ VI1)
else id
go :: HasCallStack => Value -> Formula -> Value -> Value -> Value
go VPi{} phi u a0 =
let
dom x = let VPi _ d _ = fam x in d
rng x = let VPi _ d _ = fam x in d
ai1 = dom VI0
y' i y = fill env i (dom . inot . fam) P.Bot (VSystem emptySystem) y
ybar i y = y' (inot i) y
in VLam "x" ai1 \arg ->
comp env
(VLam ivar VI (\i -> rng (ybar i arg)))
phi
(VLam "i" VI \i -> mapVSystem (u @@ i) (@@ ybar i arg))
(a0 @@ ybar VI0 arg)
go VSigma{} phi u a0 =
let
dom x = let VSigma _ d _ = fam x in d
rng x = let VSigma _ d _ = fam x in d
a i = fill env i (dom . fam) phi (VLam "j" VI \v -> mapVSystem (u @@ v) proj1) (proj1 a0)
c1 = comp env (VLam ivar VI (getd . fam)) phi (VLam "i" VI \v -> mapVSystem (u @@ v) proj1) (proj1 a0)
c2 = comp env (VLam ivar VI (apr (a VI1) . fam)) phi (VLam "i" VI \v -> mapVSystem (u @@ v) proj2) (proj2 a0)
getd (VSigma _ d _) = d
apr x (VSigma _ _ r) = r x
in VPair c1 c2
go VPath{} phi p p0 =
let
~(VPath ai1 u1 v1) = fam VI1
~(VPath ai0 u0 v0) = fam VI0
getA (VPath a _ _) = a
u' x = let ~(VPath _ u _) = fam x in u
v' x = let ~(VPath _ _ v) = fam x in v
in
VLine (ai1 @@ VI1) u1 v1 \j ->
let
jc = reduceCube' env j
in comp env (VLam ivar VI (getA . fam))
(orFormula [phi, jc, notFormula jc])
(VLam "j" VI \v ->
let
VSystem (FMap sys) = p @@ v
sys' = fmap (flip (pathp env ai0 u0 v0) j) sys
in mkVSystem $ Map.fromList [(phi, mapVSystem (p @@ v) (flip (pathp env ai0 u0 v0) j))
, (notFormula jc, u' v), (jc, v' v)])
(pathp env (ai0 @@ VI0) u0 v0 p0 j)
go a P.Top u a0 = u @@ VI1
go a phi u a0 = maybeAddEq stuck
comp env va phi u a0 =
if phi == P.Top
then VEqGlued (VComp va phi' u a0) (u @@ VI1)
else VComp va phi' u a0
where
phi' = toValue phi
mkVSystem :: Map.Map Formula Value -> Value
mkVSystem mp
| Just e <- Map.lookup P.Top mp = e
| otherwise = VSystem $ FMap $ Map.filterWithKey f mp
where
f P.Bot _ = False
f _ _ = True
reduceCube' :: Env -> Value -> Formula
reduceCube' env = fromJust . reduceCube env
mapVSystem :: Value -> (Value -> Value) -> Value
mapVSystem (VSystem ss) f = VSystem (mapSystem ss f)
mapVSystem x f = f x
evalSystem :: Env -> Map.Map Formula Term -> Value
evalSystem env face = mk . Map.mapMaybeWithKey go $ face where
go :: Formula -> Term -> Maybe Value
go face tm
| VI0 <- toValue' env face = Nothing
| otherwise = Just (eval env tm)
differsFromEnv :: String -> Bool -> Bool
differsFromEnv x True =
case Map.lookup x (names env) of
Just (VI, VI0) -> True
_ -> False
differsFromEnv x False =
case Map.lookup x (names env) of
Just (VI, VI1) -> True
_ -> False
mk x = case Map.toList x of
[(_, x)] -> x
_ -> mkVSystem x
eval :: Env -> Term -> Value
eval env = \case
Var v ->
case Map.lookup v (names env) of
Just (_, vl) -> vl
Nothing -> error $ "variable not in scope: " ++ show v
App f x -> eval env f @@ eval env x
Lam s d b ->
let d' = eval env d
in VLam s d' \a -> eval env{ names = Map.insert s (d', a) (names env) } b
Let s t b d ->
let b' = eval env b
t' = eval env t
in eval env{ names = Map.insert s (t', b') (names env) } d
Pi s d r ->
let d' = eval env d
in VPi s d' \a -> eval env{ names = Map.insert s (d', a) (names env) } r
Sigma s d r ->
let d' = eval env d
in VSigma s d' \a -> eval env{ names = Map.insert s (d', a) (names env) } r
Pair a b -> VPair (eval env a) (eval env b)
Proj1 x -> proj1 (eval env x)
Proj2 y -> proj2 (eval env y)
Type -> VType
I -> VI
I0 -> VI0
I1 -> VI1
Path p x y -> VPath (eval env p) (eval env x) (eval env y)
Partial r a -> VPartial (eval env r) (eval env a)
PathI p x y s e -> VLine (eval env p) (eval env x) (eval env y) (\ a -> eval env{ names = Map.insert s (VI, a) (names env) } e)
PathP p x y f i -> pathp env (eval env p) (eval env x) (eval env y) (eval env f) (eval env i)
Sub p x y -> VSub (eval env p) (eval env x) (eval env y)
InclSub a phi u a0 -> VOfSub (eval env a) (eval env phi) (eval env u) (eval env a0)
IAnd x y -> iand (eval env x) (eval env y)
IOr x y -> ior (eval env x) (eval env y)
INot x -> inot (eval env x)
Comp a phi u a0 ->
case reduceCube env (eval env phi) of
Just formula -> comp env (eval env a) formula (eval env u) (eval env a0)
Nothing -> VComp (eval env a) (eval env phi) (eval env u) (eval env a0)
System fs -> evalSystem env (getSystem fs)
data UnifyError
= Mismatch Value Value
| NotPiType Value
| NotPartialType Formula Value
| NotSigmaType Value
deriving (Show, Typeable, Exception)
unify :: Env -> Value -> Value -> IO ()
unify env (VEqGlued a b) c =
unify env a c `catch` \e -> const (unify env b c) (e :: UnifyError)
unify env c (VEqGlued a b) =
unify env c a `catch` \e -> const (unify env c b) (e :: UnifyError)
unify env (VLine a x y f) e = unify env (f (VVar "i")) (pathp env a x y e (VVar "i"))
unify env e (VLine a x y f) = unify env (f (VVar "i")) (pathp env a x y e (VVar "i"))
unify env (VPartial r b) (VPartial r' b') = do
unify env b b'
case sameCube env r r' of
Just True -> pure ()
_ -> unify env r r'
unify env (VPartial r b) x = do
case sameCube env r VI1 of
Just True -> pure ()
_ -> unify env r VI1
unify env b x
unify env x (VPartial r b) = do
case sameCube env r VI1 of
Just True -> pure ()
_ -> unify env r VI1
unify env x b
unify env (VSub a phi _u0) vl = unify env a vl
unify env u1 (VOfSub _a phi u0 a) = do
case sameCube env phi VI1 of
Just True -> unify env u1 u0
_ -> unify env u1 a
unify env (VOfSub _a phi u0 a) u1 = do
case sameCube env phi VI1 of
Just True -> unify env u1 u0
_ -> unify env u1 a
unify env vl1@(VNe x sp) vl2@(VNe y sp')
| x == y = traverse_ (uncurry unifySp) (zip sp sp')
| otherwise = throwIO $ Mismatch vl1 vl2
where
unifySp (PApp x) (PApp y) = unify env x y
unifySp (PPathP _a _x _y i) (PPathP _a' _x' _y' i') = unify env i i'
unifySp PProj1 PProj1 = pure ()
unifySp PProj2 PProj2 = pure ()
unify env (VLam x _ k) e = unify env (k (VVar x)) (e @@ VVar x)
unify env e (VLam x _ k) = unify env (e @@ VVar x) (k (VVar x))
unify env (VPi x d r) (VPi _ d' r') = do
unify env d d'
unify env (r (VVar x)) (r' (VVar x))
unify env (VSigma x d r) (VSigma _ d' r') = do
unify env d d'
unify env (r (VVar x)) (r' (VVar x))
unify env VType VType = pure ()
unify env VI VI = pure ()
unify env (VPair a b) (VPair c d) = unify env a c *> unify env b d
unify env (VPath a x y) (VPath a' x' y') = unify env a a' *> unify env x x' *> unify env y y'
unify env (VSystem fs) vl
| ((_, vl'):_) <- Map.toList (Map.filterWithKey (\f _ -> isTrue (toValue' env f)) (getSystem fs))
= unify env vl' vl
unify env vl (VSystem fs)
| ((_, vl'):_) <- Map.toList (Map.filterWithKey (\f _ -> isTrue (toValue' env f)) (getSystem fs))
= unify env vl' vl
unify env x y =
case sameCube env x y of
Just True -> pure ()
_ -> throwIO $ Mismatch x y
reduceCube :: Env -> Value -> Maybe Formula
reduceCube env x = fmap (toDNF . simplify) (toFormula x) where
simplify :: Formula -> Formula
simplify (P.Is0 x) =
case Map.lookup x (names env) of
Just (VI, VI0) -> P.Top
Just (VI, VI1) -> P.Bot
_ -> P.Is0 x
simplify (P.Is1 x) =
case Map.lookup x (names env) of
Just (VI, VI1) -> P.Top
Just (VI, VI0) -> P.Bot
_ -> P.Is0 x
simplify (P.And x y) = P.And (simplify x) (simplify y)
simplify (P.Or x y) = P.Or (simplify x) (simplify y)
simplify x = x
sameCube :: Env -> Value -> Value -> Maybe Bool
sameCube env x y =
case (reduceCube env x, reduceCube env y) of
(Just x, Just y) -> Just (x == y)
_ -> Nothing
toFormula :: Value -> Maybe Formula
toFormula VI0 = Just P.Bot
toFormula VI1 = Just P.Top
toFormula (VNe x []) = Just (P.Is1 x)
toFormula (VINot f) = notFormula <$> toFormula f
toFormula (VIAnd x y) = do
s <- toFormula y
t <- toFormula x
pure $ andFormula [s, t]
toFormula (VIOr x y) = do
s <- toFormula y
t <- toFormula x
pure $ orFormula [s, t]
toFormula _ = Nothing
faceInEnv :: Env -> Face -> Bool
faceInEnv e f = Map.isSubmapOf (getFace f) (faceOfEnv (names e)) where
faceOfEnv = Map.map (\(_, v) -> case v of { VI1 -> True; VEqGlued _ VI1 -> True; _ -> False }) . Map.filter (\(_, v) -> isI v)
isI VI1 = True
isI VI0 = True
isI (VEqGlued _ x) = isI x
isI _ = False
isPiType :: Value -> IO (String, Value, Value -> Value)
isPiType (VPi x d r) = pure (x, d, r)
isPiType x = throwIO $ NotPiType x
isSigmaType :: Value -> IO (String, Value, Value -> Value)
isSigmaType (VSigma x d r) = pure (x, d, r)
isSigmaType x = throwIO $ NotSigmaType x
isPiOrPathType :: Value -> IO (Either (String, Value, Value -> Value) (Value, Value, Value))
isPiOrPathType (VPi x d r) = pure (Left (x, d, r))
isPiOrPathType (VPath x d r) = pure (Right (x, d, r))
isPiOrPathType x = throwIO $ NotPiType x
isPartialType :: Formula -> Value -> IO (Formula, Value)
isPartialType f p@(VPartial x y) =
case toFormula x of
Just x -> pure (x, y)
Nothing -> throwIO $ NotPartialType f p
isPartialType f x = throwIO $ NotPartialType f x
getVar :: IO Value
getVar =
do
n <- atomicModifyIORef ref \x -> (x + 1, x)
pure (VVar (show n))
where
ref :: IORef Int
ref = unsafePerformIO (newIORef 0)
{-# NOINLINE ref #-}
fill :: Env
-> Value
-> (Value -> Value) -- (Γ i : I, A : Type)
-> Formula -- (phi : I)
-> Value -- (u : (i : I) -> Partial phi (A i))
-> Value -- (Sub (A i0) phi (u i0))
-> Value -- -> A i
fill env i a phi u a0 =
comp env
(VLam "j" VI \j -> a (i `iand` j))
(phi `P.Or` ifc)
(VLam "j" VI \j ->
mkVSystem (Map.fromList [ (phi, uiand j)
, (notFormula ifc, a0) ]))
a0
where
uiand j = u @@ (i `iand` j)
ifc = fromJust (reduceCube env i)
toValue :: Formula -> Value
toValue P.Top = VI1
toValue P.Bot = VI0
toValue (P.And x y) = toValue x `iand` toValue y
toValue (P.Or x y) = toValue x `ior` toValue y
toValue (P.Is0 x) = inot (VVar x)
toValue (P.Is1 x) = VVar x
toValue' :: Env -> Formula -> Value
toValue' env P.Top = VI1
toValue' env P.Bot = VI0
toValue' env (P.And x y) = toValue x `iand` toValue y
toValue' env (P.Or x y) = toValue x `ior` toValue y
toValue' env (P.Is0 x) =
case Map.lookup x (names env) of
Just (VI, VI0) -> VI1
Just (VI, VI1) -> VI0
Just (VI, x) -> inot x
_ -> error $ "type error in toValue'"
toValue' env (P.Is1 x) =
case Map.lookup x (names env) of
Just (VI, x) -> x
_ -> error $ "type error in toValue'"
isTrue :: Value -> Bool
isTrue VI1 = True
isTrue _ = False