{- |

Module : $Header$

Copyright : (c) Christian Maeder and Uni Bremen 2003

Licence : similar to LGPL, see HetCATS/LICENCE.txt or LIZENZ.txt

Maintainer : maeder@tzi.de

Stability : experimental

Portability : portable

constraint resolution

-}

module HasCASL.Constrain where

import HasCASL.Unify

import HasCASL.As

import HasCASL.AsUtils

import HasCASL.Le

import HasCASL.TypeAna

import HasCASL.ClassAna

import qualified Common.Lib.Set as Set

import qualified Common.Lib.Map as Map

import qualified Common.Lib.Rel as Rel

import Common.Lib.State

import Common.PrettyPrint

import Common.Lib.Pretty

import Common.Keywords

import Common.Id

import Common.Result

import Data.List

import Data.Maybe

data Constrain = Kinding Type Kind

| Subtyping Type Type

deriving (Eq, Ord, Show)

instance PrettyPrint Constrain where

printText0 ga c = case c of

Kinding ty k -> printText0 ga ty <+> colon

<+> printText0 ga k

Subtyping t1 t2 -> printText0 ga t1 <+> text lessS

<+> printText0 ga t2

instance PosItem Constrain where

get_pos c = case c of

Kinding ty _ -> get_pos ty

Subtyping t1 t2 -> get_pos t1 ++ get_pos t2

type Constraints = Set.Set Constrain

noC :: Constraints

noC = Set.empty

joinC :: Constraints -> Constraints -> Constraints

joinC = Set.union

insertC :: Constrain -> Constraints -> Constraints

insertC c = case c of

Subtyping t1 t2 -> if t1 == t2 then id else Set.insert c

_ -> Set.insert c

substC :: Subst -> Constraints -> Constraints

substC s = Set.fold (insertC . ( \ c -> case c of

Kinding ty k -> Kinding (subst s ty) k

Subtyping t1 t2 -> Subtyping (subst s t1) $ subst s t2)) noC

simplify :: TypeMap -> Constraints -> ([Diagnosis], Constraints)

simplify tm rs =

if Set.isEmpty rs then ([], noC)

else let (r, rt) = Set.deleteFindMin rs

Result ds m = entail tm r

(es, cs) = simplify tm rt

in (ds ++ es, case m of

Just _ -> cs

Nothing -> insertC r cs)

entail :: Monad m => TypeMap -> Constrain -> m ()

entail tm p =

do is <- byInst tm p

mapM_ (entail tm) $ Set.toList is

byInst :: Monad m => TypeMap -> Constrain -> m Constraints

byInst tm c = case c of

Kinding ty k -> case ty of

ExpandedType _ t -> byInst tm $ Kinding t k

_ -> case k of

Intersection l _ -> if null l then return noC else

do pss <- mapM (\ ik -> byInst tm (Kinding ty ik)) l

return $ Set.unions pss

ExtKind ek _ _ -> byInst tm (Kinding ty ek)

ClassKind _ _ -> let (topTy, args) = getTypeAppl tm ty in

case topTy of

TypeName _ kind _ -> if null args then

if lesserKind tm kind k then return noC

else fail $ expected k kind

else do

let ks = getKindAppl kind args

newKs <- dom tm k ks

return $ Set.fromList $ zipWith Kinding args newKs

_ -> error "byInst: unexpected Type"

_ -> error "byInst: unexpected Kind"

Subtyping t1 t2 -> if lesserType tm t1 t2 then return noC

else fail ("unable to prove: " ++ showPretty t1 " < "

++ showPretty t2 "")

maxKind :: TypeMap -> Kind -> Kind -> Maybe Kind

maxKind tm k1 k2 = if lesserKind tm k1 k2 then Just k1 else

if lesserKind tm k2 k1 then Just k2 else Nothing

maxKinds :: TypeMap -> [Kind] -> Maybe Kind

maxKinds tm l = case l of

[] -> Nothing

[k] -> Just k

[k1, k2] -> maxKind tm k1 k2

k1 : k2 : ks -> case maxKind tm k1 k2 of

Just k -> maxKinds tm (k : ks)

Nothing -> do k <- maxKinds tm (k2 : ks)

maxKind tm k1 k

maxKindss :: TypeMap -> [[Kind]] -> Maybe [Kind]

maxKindss tm l = let margs = map (maxKinds tm) $ transpose l in

if all isJust margs then Just $ map fromJust margs

else Nothing

dom :: Monad m => TypeMap -> Kind -> [(Kind, [Kind])] -> m [Kind]

dom tm k ks =

let fks = filter ( \ (rk, _) -> lesserKind tm rk k ) ks

margs = maxKindss tm $ map snd fks

in if null fks then fail ("class not found " ++ showPretty k "")

else case margs of

Nothing -> fail "dom: maxKind"

Just args -> if any ((args ==) . snd) fks then return args

else fail "dom: not coregular"

-- | get kind of an analyzed type

kindOfType :: TypeMap -> Type -> Kind

kindOfType tm ty = case ty of

TypeName _ k _ -> k

TypeAppl t1 t2 -> toIntersection

(concatMap snd $ getKindAppl (kindOfType tm t1) [t2])

$ posOfType t1 ++ posOfType t2

ExpandedType _ t1 -> kindOfType tm t1

FunType t1 a t2 _ ->

let i = arrowId a

Result _ mk = getIdKind tm i in case mk of

Just k -> let tn = TypeName i k 0 in

kindOfType tm (TypeAppl (TypeAppl tn t1) t2)

Nothing -> error "kindOfType: FunType"

ProductType ts ps -> let Result _ mk = getIdKind tm productId in case mk of

Nothing -> error "kindOfType: ProductType"

Just k -> let

rk = toIntersection (map fst $ getKindAppl k [ty,ty]) ps

tn = TypeName productId k 0

mkAppl [t1] = t1

mkAppl (t1:tr) = TypeAppl (TypeAppl tn t1) $ mkAppl tr

mkAppl [] = error "kindOfType: mkAppl"

in if null ts then rk else kindOfType tm (mkAppl ts)

LazyType t _ -> kindOfType tm t

KindedType _ k _ -> k

_ -> error "kindOfType"

freshTypeVarT :: TypeMap -> Type -> State Int Type

freshTypeVarT tm t =

do (var, c) <- freshVar $ posOfType t

return $ TypeName var (kindOfType tm t) c

freshVarsT :: TypeMap -> [Type] -> State Int [Type]

freshVarsT tm l = mapM (freshTypeVarT tm) l

toPairState :: State Int a -> State (Int, b) a

toPairState p =

do (a, b) <- get

let (r, c) = runState p a

put (c, b)

return r

addSubst :: Subst -> State (Int, Subst) ()

addSubst s = do

(c, o) <- get

put (c, compSubst o s)

swap :: (a, b) -> (b, a)

swap (a, b) = (b, a)

-- pre: shapeMatch succeeds

shapeMgu :: TypeMap -> [(Type, Type)] -> State (Int, Subst) [(Type, Type)]

shapeMgu tm cs =

let (atoms, structs) = partition ( \ p -> case p of

(TypeName _ _ _, TypeName _ _ _) -> True

_ -> False) cs

in if null structs then return atoms else

let p@(t1, t2) = head structs

tl = tail structs

rest = tl ++ atoms

in case p of

(ExpandedType _ t, _) -> shapeMgu tm ((t, t2) : rest)

(_, ExpandedType _ t) -> shapeMgu tm ((t1, t) : rest)

(LazyType t _, _) -> shapeMgu tm ((t, t2) : rest)

(_, LazyType t _) -> shapeMgu tm ((t1, t) : rest)

(KindedType t _ _, _) -> shapeMgu tm ((t, t2) : rest)

(_, KindedType t _ _) -> shapeMgu tm ((t1, t) : rest)

(TypeName _ _ v1, _) -> if (v1 > 0) then case t2 of

ProductType ts ps -> do

nts <- toPairState $ freshVarsT tm ts

let s = Map.single v1 $ ProductType nts ps

addSubst s

shapeMgu tm (zip nts ts ++ subst s rest)

FunType t3 ar t4 ps -> do

v3 <- toPairState $ freshTypeVarT tm t3

v4 <- toPairState $ freshTypeVarT tm t4

let s = Map.single v1 $ FunType v3 ar v4 ps

addSubst s

shapeMgu tm ((t3, v3) : (v4, t4) : subst s rest)

_ -> do

let (topTy, args) = getTypeAppl tm t2

(_, ks) = getRawKindAppl (rawKind $ kindOfType tm topTy) args

vs <- toPairState $ freshVarsT tm args

let s = Map.single v1 $ mkTypeAppl topTy vs

addSubst s

shapeMgu tm (concat (zipWith zipC ks $ zip vs args)

++ subst s rest)

else error ("shapeMgu: " ++ showPretty t1 " < " ++ showPretty t2 "")

(_, TypeName _ _ _) -> do ats <- shapeMgu tm ((t2, t1) : map swap rest)

return $ map swap ats

(ProductType s1 _, ProductType s2 _) -> shapeMgu tm (zip s1 s2 ++ rest)

(FunType t3 a1 t4 _, FunType t5 a2 t6 _) ->

let arr a = TypeName (arrowId a) funKind 0 in

shapeMgu tm ((arr a1, arr a2) : (t5, t3) : (t4, t6) : rest)

_ -> let (top1, as1) = getTypeAppl tm t1

(top2, as2) = getTypeAppl tm t2

in case (top1, top2) of

(TypeName _ k1 _, TypeName _ k2 _) ->

let r1 = rawKind k1

r2 = rawKind k2

(_, ks) = getRawKindAppl r1 as1

in if (r1 == r2 && length as1 == length as2) then

shapeMgu tm ((top1, top2) :

concat (zipWith zipC ks $ zip as1 as2)

++ rest)

else error "shapeMgu"

_ -> error ("shapeMgu: " ++ showPretty t1 " < " ++ showPretty t2 "")

zipC :: Kind -> (Type, Type) -> [(Type, Type)]

zipC k p = let q = swap p in case k of

ExtKind _ CoVar _ -> [p]

ExtKind _ ContraVar _ -> [q]

_ -> [p,q]

shapeUnify :: TypeMap -> [(Type, Type)] -> State Int (Subst, [(Type, Type)])

shapeUnify tm l = do

c <- get

let (r, (n, s)) = runState (shapeMgu tm l) (c, eps)

put n

return (s, r)

getRawKindAppl :: Kind -> [a] -> (Kind, [Kind])

getRawKindAppl k args = if null args then (k, []) else

case k of

FunKind k1 k2 _ -> let (rk, ks) = getRawKindAppl k2 (tail args)

in (rk, k1 : ks)

ExtKind ek _ _ -> getRawKindAppl ek args

_ -> error ("getRawKindAppl " ++ show k)

-- input an atomized constraint list

collapser :: Rel.Rel Type -> Result Subst

collapser r =

let t = Rel.sccOfClosure r

ks = map (Set.partition ( \ e -> case e of

TypeName _ _ n -> n==0

_ -> error "collapser")) t

ws = filter (\ p -> Set.size (fst p) > 1) ks

in if null ws then

return $ foldr ( \ (cs, vs) s ->

if Set.isEmpty cs then

extendSubst s $ Set.deleteFindMin vs

else extendSubst s (Set.findMin cs, vs)) eps ks

else Result

(map ( \ (cs, _) ->

let (c1, rs) = Set.deleteFindMin cs

c2 = Set.findMin rs

in Diag Hint ("contradicting type inclusions for '"

++ showPretty c1 "' and '"

++ showPretty c2 "'") []) ws) Nothing

extendSubst :: Subst -> (Type, Set.Set Type) -> Subst

extendSubst s (t, vs) = Set.fold ( \ (TypeName _ _ n) ->

Map.insert n t) s vs

-- | partition into qualification and subtyping constraints

partitionC :: Constraints -> (Constraints, Constraints)

partitionC = Set.partition ( \ c -> case c of

Kinding _ _ -> True

Subtyping _ _ -> False)

-- | convert subtypings constrains to a pair list

toListC :: Constraints -> [(Type, Type)]

toListC l = [ (t1, t2) | Subtyping t1 t2 <- Set.toList l ]

preClose :: TypeMap -> Constraints

-> State Int (Result (Subst, Constraints))

preClose tm cs = do

Result ds mr <- shapeRel tm cs

return $ Result ds $ case mr of

Nothing -> Nothing

Just (s, qs, r) -> Just (s, foldr ( \ (a, b) ->

insertC (Subtyping a b)) qs $ Rel.toList r)

shapeRel :: TypeMap -> Constraints

-> State Int (Result (Subst, Constraints, Rel.Rel Type))

shapeRel tm cs =

let (qs, subS) = partitionC cs

subL = toListC subS

in case shapeMatch tm (map fst subL) $ map snd subL of

Result ds Nothing -> return $ Result ds Nothing

_ -> do (s1, atoms) <- shapeUnify tm subL

let r = Rel.transClosure $ Rel.fromList $ subst s1 atoms

es = Map.foldWithKey ( \ t1 st l1 ->

case t1 of

TypeName _ _ 0 -> Set.fold ( \ t2 l2 ->

case t2 of

TypeName _ _ 0 -> if lesserType tm t1 t2

then l2 else (t1, t2) : l2

_ -> l2) l1 st

_ -> l1) [] $ Rel.toMap r

return $ if null es then

case collapser r of

Result ds Nothing -> Result ds Nothing

Result _ (Just s2) ->

let s = compSubst s1 s2

r2 = Rel.fromList $ subst s2 atoms

in return (s, substC s qs, r2)

else Result (map ( \ (t1, t2) ->

mkDiag Hint "rejected" $

Subtyping t1 t2) es) Nothing

-- | compute monotonicity of a type variable

monotonic :: TypeMap -> Int -> Type -> (Bool, Bool)

monotonic tm v t =

case t of

TypeName _ _ i -> (True, i /= v)

ExpandedType _ t2 -> monotonic tm v t2

KindedType tk _ _ -> monotonic tm v tk

LazyType tl _ -> monotonic tm v tl

_ -> let (top, args) = getTypeAppl tm t in case top of

TypeName _ k _ ->

let ks = snd $ getRawKindAppl (rawKind k) args

(bs1, bs2) = unzip $ zipWith ( \ rk a ->

let (b1, b2) = monotonic tm v a

in case rk of

ExtKind _ CoVar _ -> (b1, b2)

ExtKind _ ContraVar _ -> (b2, b1)

_ -> (b1 && b2, b1 && b2)) ks args

in (and bs1, and bs2)

_ -> error "monotonic"

-- | find monotonicity based instantiation

monoSubst :: TypeMap -> Rel.Rel Type -> Type -> Subst

monoSubst tm r t =

let varSet = Set.fromList . leaves (> 0)

vs = Set.toList $ Set.union (varSet t) $ Set.unions $ map varSet

$ Set.toList $ Rel.nodes r

monos = filter ( \ (i, TypeArg n k _ _) -> case monotonic tm i t of

(True, _) -> 1 == Set.size

(Rel.predecessors r $ TypeName n k i)

_ -> False) vs

antis = filter ( \ (i, TypeArg n k _ _) -> case monotonic tm i t of

(_, True) -> 1 == Set.size

(Rel.succs r $ TypeName n k i)

_ -> False) vs

resta = filter ( \ (i, TypeArg n k _ _) -> case monotonic tm i t of

(True, True) -> 1 < Set.size

(Rel.succs r $ TypeName n k i)

_ -> False) vs

restb = filter ( \ (i, TypeArg n k _ _) -> case monotonic tm i t of

(True, True) -> 1 < Set.size

(Rel.predecessors r $ TypeName n k i)

_ -> False) vs

in if null antis then

if null monos then

if null resta then

if null restb then eps else

let (i, TypeArg n k _ _) = head restb

tn = TypeName n k i

s = Rel.predecessors r tn

sl = Set.delete tn $ foldl1 Set.intersection

$ map (Rel.succs r)

$ Set.toList s

in Map.single i $ Set.findMin $ if Set.isEmpty sl then s

else sl

else let (i, TypeArg n k _ _) = head resta

tn = TypeName n k i

s = Rel.succs r tn

sl = Set.delete tn $ foldl1 Set.intersection

$ map (Rel.predecessors r)

$ Set.toList s

in Map.single i $ Set.findMin $ if Set.isEmpty sl then s

else sl

else Map.fromAscList $ map ( \ (i, TypeArg n k _ _) ->

(i, Set.findMin $ Rel.predecessors r $ TypeName n k i)) monos

else Map.fromAscList $ map ( \ (i, TypeArg n k _ _) ->

(i, Set.findMin $ Rel.succs r $ TypeName n k i)) antis

monoSubsts :: TypeMap -> Rel.Rel Type -> Type -> Subst

monoSubsts tm r t =

let s = monoSubst tm (Rel.transReduce $ Rel.irreflex r) t in

if Map.isEmpty s then s else

compSubst s $

monoSubsts tm (Rel.transReduce $ Rel.irreflex $

Rel.image (subst s) r)

$ subst s t

fromTypeMap :: TypeMap -> Rel.Rel Type

fromTypeMap = Map.foldWithKey (\ t ti r ->

foldr (Rel.insert (TypeName t (typeKind ti) 0)) r

[ ty | ty@(TypeName _ _ _) <-

superTypes ti ]) Rel.empty