{- |

Module : $Header$

Description : Overload resolution

Copyright : (c) Martin Kuehl, T. Mossakowski, C. Maeder, 2004-2007

License : GPLv2 or higher, see LICENSE.txt

Maintainer : Christian.Maeder@dfki.de

Stability : provisional

Portability : portable

Overload resolution (injections are inserted separately)

Follows Sect. III:3.3 of the CASL Reference Manual.

The algorthim is from:

Till Mossakowski, Kolyang, Bernd Krieg-Brueckner:

Static semantic analysis and theorem proving for CASL.

12th Workshop on Algebraic Development Techniques, Tarquinia 1997,

LNCS 1376, p. 333-348

-}

module CASL.Overload

( minExpFORMULA

, minExpFORMULAeq

, oneExpTerm

, Min

, leqF

, leqP

, leqSort

, minimalSupers

, maximalSubs

, haveCommonSupersorts

, keepMinimals1

, keepMinimals

) where

import CASL.Sign

import CASL.AS_Basic_CASL

import qualified Common.Lib.Rel as Rel

import Common.Lib.State

import Common.Id

import Common.GlobalAnnotations

import Common.DocUtils

import Common.Result

import Common.Partial

import Common.Utils

import qualified Data.Map as Map

import qualified Data.Set as Set

import Control.Monad

-- | the type of the type checking function of extensions

type Min f e = Sign f e -> f -> Result f

{- ----------------------------------------------------------

- Minimal expansion of a formula -

Expand a given formula by typing information.

* For non-atomic formulae, recurse through subsentences.

* For trival atomic formulae, no expansion is neccessary.

* For atomic formulae, the following cases are implemented:

+ Predication is handled by the dedicated expansion function

'minExpFORMULApred'.

+ Existl_equation and Strong_equation are handled by the dedicated

expansion function 'minExpFORMULAeq'.

+ Definedness is handled by expanding the subterm.

+ Membership is handled like Cast

---------------------------------------------------------- -}

minExpFORMULA

:: (GetRange f, Pretty f, TermExtension f)

=> Min f e -> Sign f e -> FORMULA f -> Result (FORMULA f)

minExpFORMULA mef sign formula = let sign0 = sign { envDiags = [] } in

case formula of

Quantification q vars f pos -> do

-- add 'vars' to signature

let sign' = execState (mapM_ addVars vars) sign0

Result (envDiags sign') $ Just ()

f' <- minExpFORMULA mef sign' f

return (Quantification q vars f' pos)

Conjunction fs pos -> do

fs' <- mapR (minExpFORMULA mef sign) fs

return (Conjunction fs' pos)

Disjunction fs pos -> do

fs' <- mapR (minExpFORMULA mef sign) fs

return (Disjunction fs' pos)

Implication f1 f2 b pos ->

joinResultWith (\ f1' f2' -> Implication f1' f2' b pos)

(minExpFORMULA mef sign f1) $ minExpFORMULA mef sign f2

Equivalence f1 f2 pos ->

joinResultWith (\ f1' f2' -> Equivalence f1' f2' pos)

(minExpFORMULA mef sign f1) $ minExpFORMULA mef sign f2

Negation f pos -> do

f' <- minExpFORMULA mef sign f

return (Negation f' pos)

Predication (Pred_name ide) terms pos

-> minExpFORMULApred mef sign ide Nothing terms pos

Predication (Qual_pred_name ide ty pos1) terms pos2

-> minExpFORMULApred mef sign ide (Just $ toPredType ty)

terms (pos1 `appRange` pos2)

Existl_equation term1 term2 pos

-> minExpFORMULAeq mef sign Existl_equation term1 term2 pos

Strong_equation term1 term2 pos

-> minExpFORMULAeq mef sign Strong_equation term1 term2 pos

Definedness term pos -> do

t <- oneExpTerm mef sign term

return (Definedness t pos)

Membership term sort pos -> do

ts <- minExpTerm mef sign term

let fs = map (concatMap ( \ t ->

let s = sortOfTerm t in

if leqSort sign sort s then

[Membership t sort pos] else

map ( \ c ->

Membership (Sorted_term t c pos) sort pos)

$ minimalSupers sign s sort)) ts

isUnambiguous (globAnnos sign) formula fs pos

ExtFORMULA f -> fmap ExtFORMULA $ mef sign f

QuantOp o ty f -> do

let sign' = sign0 { opMap = addOpTo o (toOpType ty) $ opMap sign0 }

Result (envDiags sign') $ Just ()

f' <- minExpFORMULA mef sign' f

return $ QuantOp o ty f'

QuantPred p ty f -> do

let pm = predMap sign0

ptys = Map.findWithDefault Set.empty p pm

sign' = sign0

{ predMap = Map.insert p (Set.insert (toPredType ty) ptys) pm }

Result (envDiags sign') $ Just ()

f' <- minExpFORMULA mef sign' f

return $ QuantPred p ty f'

_ -> return formula -- do not fail even for unresolved cases

-- | test if a term can be uniquely resolved

oneExpTerm :: (GetRange f, Pretty f, TermExtension f)

=> Min f e -> Sign f e -> TERM f -> Result (TERM f)

oneExpTerm minF sign term = do

ts <- minExpTerm minF sign term

isUnambiguous (globAnnos sign) term ts nullRange

{- ----------------------------------------------------------

- Minimal expansion of an equation formula -

see minExpTermCond

---------------------------------------------------------- -}

minExpFORMULAeq :: (GetRange f, Pretty f, TermExtension f)

=> Min f e -> Sign f e -> (TERM f -> TERM f -> Range -> FORMULA f)

-> TERM f -> TERM f -> Range -> Result (FORMULA f)

minExpFORMULAeq mef sign eq term1 term2 pos = do

ps <- minExpTermCond mef sign ( \ t1 t2 -> eq t1 t2 pos)

term1 term2 pos

isUnambiguous (globAnnos sign) (eq term1 term2 pos) ps pos

-- | check if there is at least one solution

hasSolutions :: Pretty f => GlobalAnnos -> f -> [[f]] -> Range

-> Result [[f]]

hasSolutions ga topterm ts pos = let terms = filter (not . null) ts in

if null terms then Result

[Diag Error ("no typing for: " ++ showGlobalDoc ga topterm "")

pos] Nothing

else return terms

-- | check if there is a unique equivalence class

isUnambiguous :: Pretty f => GlobalAnnos -> f -> [[f]] -> Range

-> Result f

isUnambiguous ga topterm ts pos = do

terms <- hasSolutions ga topterm ts pos

case terms of

[ term : _ ] -> return term

_ -> Result [Diag Error ("ambiguous term\n " ++

showSepList (showString "\n ") (showGlobalDoc ga)

(take 5 $ map head terms) "") pos] Nothing

checkIdAndArgs :: Id -> [a] -> Range -> Result Int

checkIdAndArgs ide args poss =

let nargs = length args

pargs = placeCount ide

in if isMixfix ide && pargs /= nargs then

Result [Diag Error

("expected " ++ shows pargs " argument(s) of mixfix identifier '"

++ showDoc ide "' but found " ++ shows nargs " argument(s)")

poss] Nothing

else return nargs

noOpOrPred :: Pretty t => [a] -> String -> Maybe t -> Id -> Range

-> Int -> Result ()

noOpOrPred ops str mty ide pos nargs =

when (null ops) $ case mty of

Nothing -> Result [Diag Error

("no " ++ str ++ " with " ++ shows nargs " argument"

++ (if nargs == 1 then "" else "s") ++ " found for '"

++ showDoc ide "'") pos] Nothing

Just ty -> Result [Diag Error

("no " ++ str ++ " with profile '"

++ showDoc ty "' found for '"

++ showDoc ide "'") pos] Nothing

{- ----------------------------------------------------------

- Minimal expansion of a predication formula -

see minExpTermAppl

---------------------------------------------------------- -}

minExpFORMULApred :: (GetRange f, Pretty f, TermExtension f)

=> Min f e -> Sign f e -> Id -> Maybe PredType -> [TERM f] -> Range

-> Result (FORMULA f)

minExpFORMULApred mef sign ide mty args pos = do

nargs <- checkIdAndArgs ide args pos

let -- predicates matching that name in the current environment

preds' = Set.filter ((nargs ==) . length . predArgs) $

Map.findWithDefault Set.empty ide $ predMap sign

preds = case mty of

Nothing -> map (pSortBy predArgs sign)

$ Rel.leqClasses (leqP' sign) preds'

Just ty -> [[ty] | Set.member ty preds']

noOpOrPred preds "predicate" mty ide pos nargs

expansions <- mapM (minExpTerm mef sign) args

let getProfiles cs = map (getProfile cs) preds

getProfile cs ps = [ (pred', ts) |

pred' <- ps,

ts <- cs,

and $ zipWith (leqSort sign)

(map sortOfTerm ts)

(predArgs pred') ]

qualForms = qualifyPreds ide pos

$ concatMap (getProfiles . combine)

$ combine expansions

isUnambiguous (globAnnos sign)

(Predication (Pred_name ide) args pos) qualForms pos

qualifyPreds :: Id -> Range -> [[(PredType, [TERM f])]] -> [[FORMULA f]]

qualifyPreds ide = map . map . qualifyPred ide

-- | qualify a single pred, given by its signature and its arguments

qualifyPred :: Id -> Range -> (PredType, [TERM f]) -> FORMULA f

qualifyPred ide pos (pred', terms') =

Predication (Qual_pred_name ide (toPRED_TYPE pred') pos) terms' pos

-- | expansions of an equation formula or a conditional

minExpTermEq :: (GetRange f, Pretty f, TermExtension f)

=> Min f e -> Sign f e -> TERM f -> TERM f -> Result [[(TERM f, TERM f)]]

minExpTermEq mef sign term1 term2 = do

exps1 <- minExpTerm mef sign term1

exps2 <- minExpTerm mef sign term2

return $ map (minimizeEq sign . getPairs) $ combine [exps1, exps2]

getPairs :: [[TERM f]] -> [(TERM f, TERM f)]

getPairs cs = [ (t1, t2) | [t1, t2] <- combine cs ]

minimizeEq :: TermExtension f => Sign f e -> [(TERM f, TERM f)]

-> [(TERM f, TERM f)]

minimizeEq s = keepMinimals s (sortOfTerm . snd)

. keepMinimals s (sortOfTerm . fst)

{- ----------------------------------------------------------

- Minimal expansion of a term -

Expand a given term by typing information.

* 'Qual_var' terms are handled by 'minExpTerm_var'

* 'Application' terms are handled by 'minExpTermOp'.

* 'Conditional' terms are handled by 'minExpTermCond'.

---------------------------------------------------------- -}

minExpTerm :: (GetRange f, Pretty f, TermExtension f)

=> Min f e -> Sign f e -> TERM f -> Result [[TERM f]]

minExpTerm mef sign top = let ga = globAnnos sign in case top of

Qual_var var sort _ -> let ts = minExpTermVar sign var (Just sort) in

if null ts then mkError "no matching qualified variable found" var

else return ts

Application op terms pos -> minExpTermOp mef sign op terms pos

Sorted_term term sort pos -> do

expandedTerm <- minExpTerm mef sign term

-- choose expansions that fit the given signature, then qualify

let validExps =

map (filter (maybe True (flip (leqSort sign) sort)

. optSortOfTerm (const Nothing)))

expandedTerm

hasSolutions ga top (map (map (\ t ->

Sorted_term t sort pos)) validExps) pos

Cast term sort pos -> do

expandedTerm <- minExpTerm mef sign term

-- find a unique minimal common supersort

let ts = map (concatMap (\ t -> let s = sortOfTerm t in

if leqSort sign sort s then

if leqSort sign s sort then [t] else

[Cast t sort pos] else

map ( \ c ->

Cast (Sorted_term t c pos) sort pos)

$ minimalSupers sign s sort)) expandedTerm

hasSolutions ga top ts pos

Conditional term1 formula term2 pos -> do

f <- minExpFORMULA mef sign formula

ts <- minExpTermCond mef sign ( \ t1 t2 -> Conditional t1 f t2 pos)

term1 term2 pos

hasSolutions ga (Conditional term1 formula term2 pos) ts pos

ExtTERM t -> do

nt <- mef sign t

return [[ExtTERM nt]]

_ -> mkError "unexpected kind of term" top

-- | Minimal expansion of a possibly qualified variable identifier

minExpTermVar :: Sign f e -> Token -> Maybe SORT -> [[TERM f]]

minExpTermVar sign tok ms = case Map.lookup tok $ varMap sign of

Nothing -> []

Just s -> let qv = [[Qual_var tok s nullRange]] in

case ms of

Nothing -> qv

Just s2 -> if s == s2 then qv else []

-- | minimal expansion of an (possibly qualified) operator application

minExpTermAppl :: (GetRange f, Pretty f, TermExtension f)

=> Min f e -> Sign f e -> Id -> Maybe OpType -> [TERM f] -> Range

-> Result [[TERM f]]

minExpTermAppl mef sign ide mty args pos = do

nargs <- checkIdAndArgs ide args pos

let -- functions matching that name in the current environment

ops' = Set.filter ( \ o -> length (opArgs o) == nargs) $

Map.findWithDefault Set.empty ide $ opMap sign

ops = case mty of

Nothing -> map (pSortBy opArgs sign)

$ Rel.leqClasses (leqF' sign) ops'

Just ty -> [[ty] | Set.member ty ops' ||

-- might be known to be total

Set.member ty {opKind = Total} ops' ]

noOpOrPred ops "operation" mty ide pos nargs

expansions <- mapM (minExpTerm mef sign) args

let -- generate profiles as descr. on p. 339 (Step 3)

getProfiles cs = map (getProfile cs) ops

getProfile cs os = [ (op', ts) |

op' <- os,

ts <- cs,

and $ zipWith (leqSort sign)

(map sortOfTerm ts)

(opArgs op') ]

qualTerms = qualifyOps ide pos

$ map (minimizeOp sign)

$ concatMap (getProfiles . combine)

$ combine expansions

hasSolutions (globAnnos sign)

(Application (Op_name ide) args pos) qualTerms pos

qualifyOps :: Id -> Range -> [[(OpType, [TERM f])]] -> [[TERM f]]

qualifyOps ide = map . map . qualifyOp ide

-- qualify a single op, given by its signature and its arguments

qualifyOp :: Id -> Range -> (OpType, [TERM f]) -> TERM f

qualifyOp ide pos (op', terms') =

Application (Qual_op_name ide (toOP_TYPE op') pos) terms' pos

{- ----------------------------------------------------------

- Minimal expansion of a function application or a variable -

Expand a function application by typing information.

1. First expand all argument subterms.

2. Combine these expansions so we compute the set of tuples

{ (C_1, ..., C_n) | (C_1, ..., C_n) \in

minExpTerm(t_1) x ... x minExpTerm(t_n) }

where t_1, ..., t_n are the given argument terms.

3. For each element of this set compute the set of possible profiles

(as described on p. 339).

4. Define an equivalence relation ~ on these profiles

(as described on p. 339).

5. Separate each profile into equivalence classes by the relation ~

and take the unification of these sets.

6. Minimize each element of this unified set (as described on p. 339).

7. Transform each term in the minimized set into a qualified function

application term.

---------------------------------------------------------- -}

minExpTermOp :: (GetRange f, Pretty f, TermExtension f)

=> Min f e -> Sign f e -> OP_SYMB -> [TERM f] -> Range -> Result [[TERM f]]

minExpTermOp mef sign osym args pos = case osym of

Op_name ide@(Id ts _ _) ->

let res = minExpTermAppl mef sign ide Nothing args pos in

if null args && isSimpleId ide then

let vars = minExpTermVar sign (head ts) Nothing

in if null vars then res else

case maybeResult res of

Nothing -> return vars

Just ops -> return $ ops ++ vars

else res

Qual_op_name ide ty pos1 ->

if length args /= length (args_OP_TYPE ty) then

mkError "type qualification does not match number of arguments" ide

else minExpTermAppl mef sign ide (Just $ toOpType ty) args

(pos1 `appRange` pos)

{- ----------------------------------------------------------

- Minimal expansion of a conditional -

Expand a conditional by typing information (see minExpTermEq)

First expand the subterms and subformula. Then calculate a profile

P(C_1, C_2) for each (C_1, C_2) \in minExpTerm(t1) x minExpTerm(t_2).

Separate these profiles into equivalence classes and take the

unification of all these classes. Minimize each equivalence class.

Finally transform the eq. classes into lists of

conditionals with equally sorted terms.

---------------------------------------------------------- -}

minExpTermCond :: (GetRange f, Pretty f, TermExtension f)

=> Min f e -> Sign f e -> (TERM f -> TERM f -> a) -> TERM f -> TERM f

-> Range -> Result [[a]]

minExpTermCond mef sign f term1 term2 pos = do

pairs <- minExpTermEq mef sign term1 term2

return $ map (concatMap ( \ (t1, t2) ->

let s1 = sortOfTerm t1

s2 = sortOfTerm t2

in if s1 == s2 then [f t1 t2]

else if leqSort sign s2 s1 then

[f t1 (Sorted_term t2 s1 pos)]

else if leqSort sign s1 s2 then

[f (Sorted_term t1 s2 pos) t2]

else map ( \ s -> f (Sorted_term t1 s pos)

(Sorted_term t2 s pos))

$ minimalSupers sign s1 s2)) pairs

{- ----------------------------------------------------------

Let P be a set of equivalence classes of qualified terms.

For each C \in P, let C' choose _one_

t:s \in C for each s minimal such that t:s \in C.

That is, discard all terms whose sort is a supersort of

any other term in the same equivalence class.

---------------------------------------------------------- -}

minimizeOp :: Sign f e -> [(OpType, [TERM f])] -> [(OpType, [TERM f])]

minimizeOp sign = keepMinimals sign (opRes . fst)

-- | the (possibly incomplete) list of supersorts common to both sorts

commonSupersorts :: Bool -> Sign f e -> SORT -> SORT -> [SORT]

commonSupersorts b sign s1 s2 =

if s1 == s2 then [s1] else

let l1 = supersortsOf s1 sign

l2 = supersortsOf s2 sign in

if Set.member s2 l1 then if b then [s2] else [s1] else

if Set.member s1 l2 then if b then [s1] else [s2] else

Set.toList $ if b then Set.intersection l1 l2

else Set.intersection (subsortsOf s1 sign)

$ subsortsOf s2 sign

-- | True if both sorts have a common supersort

haveCommonSupersorts :: Bool -> Sign f e -> SORT -> SORT -> Bool

haveCommonSupersorts b s s1 = not . null . commonSupersorts b s s1

-- True if both sorts have a common subsort

haveCommonSubsorts :: Sign f e -> SORT -> SORT -> Bool

haveCommonSubsorts = haveCommonSupersorts False

-- | if True test if s1 > s2

geqSort :: Bool -> Sign f e -> SORT -> SORT -> Bool

geqSort b sign s1 s2 = s1 == s2 || let rel = sortRel sign in

if b then Rel.member s2 s1 rel else Rel.member s1 s2 rel

-- | test if s1 < s2

leqSort :: Sign f e -> SORT -> SORT -> Bool

leqSort = geqSort False

-- | minimal common supersorts of the two input sorts

minimalSupers :: Sign f e -> SORT -> SORT -> [SORT]

minimalSupers = minimalSupers1 True

minimalSupers1 :: Bool -> Sign f e -> SORT -> SORT -> [SORT]

minimalSupers1 b s s1 = keepMinimals1 b s id . commonSupersorts b s s1

-- | maximal common subsorts of the two input sorts

maximalSubs :: Sign f e -> SORT -> SORT -> [SORT]

maximalSubs = minimalSupers1 False

-- | only keep elements with minimal (and different) sorts

keepMinimals :: Sign f e -> (a -> SORT) -> [a] -> [a]

keepMinimals = keepMinimals1 True

keepMinimals1 :: Bool -> Sign f e -> (a -> SORT) -> [a] -> [a]

keepMinimals1 b s f = let lt x y = geqSort b s (f y) (f x) in keepMins lt

-- | True if both ops are in the overloading relation

leqF :: Sign f e -> OpType -> OpType -> Bool

leqF sign o1 o2 = length (opArgs o1) == length (opArgs o2) && leqF' sign o1 o2

leqF' :: Sign f e -> OpType -> OpType -> Bool

leqF' sign o1 o2 = haveCommonSupersorts True sign (opRes o1) (opRes o2) &&

and (zipWith (haveCommonSubsorts sign) (opArgs o1) (opArgs o2))

-- | True if both preds are in the overloading relation

leqP :: Sign f e -> PredType -> PredType -> Bool

leqP sign p1 p2 = length (predArgs p1) == length (predArgs p2)

&& leqP' sign p1 p2

leqP' :: Sign f e -> PredType -> PredType -> Bool

leqP' sign p1 =

and . zipWith (haveCommonSubsorts sign) (predArgs p1) . predArgs

cmpSubsort :: Sign f e -> POrder SORT

cmpSubsort sign s1 s2 =

if s1 == s2 then Just EQ else

let l1 = supersortsOf s1 sign

l2 = supersortsOf s2 sign

b = Set.member s1 l2 in

if Set.member s2 l1 then

if b then Just EQ

else Just LT

else if b then Just GT else Nothing

cmpSubsorts :: Sign f e -> POrder [SORT]

cmpSubsorts sign l1 l2 =

let l = zipWith (cmpSubsort sign) l1 l2

in if null l then Just EQ else foldr1

( \ c1 c2 -> if c1 == c2 then c1 else case (c1, c2) of

(Just EQ, _) -> c2

(_, Just EQ) -> c1

_ -> Nothing) l

pSortBy :: (a -> [SORT]) -> Sign f e -> [a] -> [a]

pSortBy f sign = let pOrd a b = cmpSubsorts sign (f a) (f b)

in concat . rankBy pOrd