1 implementation module sem
3 import qualified Data.Map as Map
5 from Data.Func import $
6 from StdFunc import o, flip, const, id
9 import Control.Monad.Trans
10 import Control.Monad.State
25 from Text import class Text(concat), instance Text String
30 :: Scheme = Forall [TVar] Type
31 :: Gamma :== 'Map'.Map String Scheme //map from Variables! to types
32 :: Substitution :== 'Map'.Map TVar Type
33 :: Constraints :== [(Type, Type)]
35 = ParseError Pos String
36 | UnifyError Pos Type Type
37 | InfiniteTypeError Pos Type
38 | FieldSelectorError Pos Type FieldSelector
39 | OperatorError Pos Op2 Type
40 | UndeclaredVariableError Pos String
41 | ArgumentMisMatchError Pos String
42 | SanityError Pos String
45 instance zero Gamma where
48 variableStream :: [TVar]
49 variableStream = map toString [1..]
51 sem :: AST -> Either [SemError] Constraints
52 sem (AST fd) = case foldM (const $ hasNoDups fd) () fd
53 >>| foldM (const isNiceMain) () fd
57 //_ = case execRWST (constraints fd) zero variableStream of
59 // Right (a, b) = Right b
61 constraints :: [FunDecl] -> Typing ()
62 constraints _ = pure ()
64 //constraints fds = mapM_ funconstraint fds >>| pure ()
66 funconstraint :: FunDecl -> Typing ()
67 funconstraint fd=:(FunDecl _ ident args mt vardecls stmts) = case mt of
68 Nothing = abort "Cannot infer functions yet"
70 //Just t = inEnv (ident, (Forall [] t)) (
71 // mapM_ vardeclconstraint vardecls >>| pure ())
73 vardeclconstraint :: VarDecl -> Typing ()
74 vardeclconstraint _ = pure ()
76 //vardeclconstraint (VarDecl p mt ident expr) = infer expr
77 //>>= \it->inEnv (ident, (Forall [] it)) (pure ())
79 hasNoDups :: [FunDecl] FunDecl -> Either SemError ()
80 hasNoDups fds (FunDecl p n _ _ _ _)
81 # mbs = map (\(FunDecl p` n` _ _ _ _)->if (n == n`) (Just p`) Nothing) fds
82 = case catMaybes mbs of
83 [] = Left $ SanityError p "HUH THIS SHOULDN'T HAPPEN"
85 [_:x] = Left $ SanityError p (concat
86 [n, " multiply defined at ", toString p])
88 hasMain :: [FunDecl] -> Either SemError ()
89 hasMain [(FunDecl _ "main" _ _ _ _):fd] = pure ()
90 hasMain [_:fd] = hasMain fd
91 hasMain [] = Left $ SanityError zero "no main function defined"
93 isNiceMain :: FunDecl -> Either SemError ()
94 isNiceMain (FunDecl p "main" as mt _ _) = case (as, mt) of
95 ([_:_], _) = Left $ SanityError p "main must have arity 0"
98 Just VoidType = pure ()
99 _ = Left $ SanityError p "main has to return Void")
100 isNiceMain _ = pure ()
102 class Typeable a where
104 subst :: Substitution a -> a
106 instance Typeable Scheme where
107 ftv (Forall bound t) = difference (ftv t) bound
108 subst s (Forall bound t) = Forall bound $ subst s_ t
109 where s_ = 'Map'.filterWithKey (\k _ -> not (elem k bound)) s
111 instance Typeable [a] | Typeable a where
112 ftv types = foldr (\t ts-> ftv t ++ ts) [] types
113 subst s ts = map (\t->subst s t) ts
115 instance Typeable Type where
116 ftv (TupleType (t1, t2)) = ftv t1 ++ ftv t2
117 ftv (ListType t) = ftv t
118 ftv (IdType tvar) = [tvar]
119 ftv (t1 ->> t2) = ftv t1 ++ ftv t2
121 subst s (TupleType (t1, t2))= TupleType (subst s t1, subst s t2)
122 subst s (ListType t1) = ListType (subst s t1)
123 subst s (t1 ->> t2) = (subst s t1) ->> (subst s t2)
124 subst s t1=:(IdType tvar) = 'Map'.findWithDefault t1 tvar s
127 instance Typeable Gamma where
128 ftv gamma = concatMap id $ map ftv ('Map'.elems gamma)
129 subst s gamma = Mapmap (subst s) gamma
131 //// ------------------------
132 //// algorithm U, Unification
133 //// ------------------------
134 instance zero Substitution where zero = 'Map'.newMap
136 compose :: Substitution Substitution -> Substitution
137 compose s1 s2 = 'Map'.union (Mapmap (subst s2) s1) s2
138 //Note: just like function compositon compose does snd first
140 occurs :: TVar a -> Bool | Typeable a
141 occurs tvar a = elem tvar (ftv a)
143 unify :: Type Type -> Either SemError Substitution
144 unify t1=:(IdType tv) t2 = unify t2 t1
145 unify t1 t2=:(IdType tv) | t1 == (IdType tv) = Right zero
146 | occurs tv t1 = Left $ InfiniteTypeError zero t1
147 | otherwise = Right $ 'Map'.singleton tv t1
148 unify (ta1->>ta2) (tb1->>tb2) = unify ta1 tb1 >>= \s1->
149 unify tb1 tb2 >>= \s2->
150 Right $ compose s1 s2
151 unify (TupleType (ta1,ta2)) (TupleType (tb1,tb2)) = unify ta1 tb1 >>= \s1->
152 unify ta2 tb2 >>= \s2->
153 Right $ compose s1 s2
154 unify (ListType t1) (ListType t2) = unify t1 t2
155 unify t1 t2 | t1 == t2 = Right zero
156 | otherwise = Left $ UnifyError zero t1 t2
158 //// ------------------------
159 //// Algorithm M, Inference and Solving
160 //// ------------------------
162 :: Typing a :== StateT (Gamma, [TVar]) (Either SemError) a
163 gamma :: Typing Gamma
165 putGamma :: Gamma -> Typing ()
166 putGamma g = modify (appFst $ const g) >>| pure ()
167 changeGamma :: (Gamma -> Gamma) -> Typing ()
168 changeGamma f = modify (appFst f) >>| pure ()
169 withGamma :: (Gamma -> a) -> Typing a
170 withGamma f = f <$> gamma
172 fresh = gets snd >>= \vars->
173 modify (appSnd $ const $ tail vars) >>|
174 pure (IdType (head vars))
176 lift :: (Either SemError a) -> Typing a
177 lift (Left e) = liftT $ Left e
178 lift (Right v) = pure v
180 //instantiate maps a schemes type variables to variables with fresh names
181 //and drops the quantification: i.e. forall a,b.a->[b] becomes c->[d]
182 instantiate :: Scheme -> Typing Type
183 instantiate (Forall bound t) =
184 mapM (const fresh) bound >>= \newVars->
185 let s = 'Map'.fromList (zip (bound,newVars)) in
188 //generalize quentifies all free type variables in a type which are not
190 generalize :: Type -> Typing Scheme
191 generalize t = gamma >>= \g-> pure $ Forall (difference (ftv t) (ftv g)) t
193 lookup :: String -> Typing Scheme
194 lookup k = gamma >>= \g-> case 'Map'.member k g of
195 False = liftT (Left $ UndeclaredVariableError zero k)
196 True = pure ('Map'.find k g)
198 //The inference class
199 //When tying it all together we will treat the program is a big
200 //let x=e1 in let y=e2 in ....
201 class infer a :: a -> Typing (Substitution, Type)
203 instance infer Expr where
205 VarExpr _ (VarDef k fs) = (\t->(zero,t)) <$> (lookup k >>= instantiate)
206 //instantiate is key for the let polymorphism!
207 //TODO: field selectors
210 infer e1 >>= \(s1, t1) ->
211 infer e2 >>= \(s2, t2) ->
213 let given = t1 ->> t2 ->> tv in
214 op2Type op >>= \expected ->
215 lift (unify expected given) >>= \s3 ->
216 pure ((compose s1 $ compose s2 s3), subst s3 tv)
219 infer e1 >>= \(s1, t1) ->
221 let given = t1 ->> tv in
222 op1Type op >>= \expected ->
223 lift (unify expected given) >>= \s2 ->
224 pure (compose s1 s2, subst s2 tv)
226 EmptyListExpr _ = (\tv->(zero,tv)) <$> fresh
228 TupleExpr _ (e1, e2) =
229 infer e1 >>= \(s1, t1) ->
230 infer e2 >>= \(s2, t2) ->
231 pure (compose s1 s2, TupleType (t1,t2))
233 FunExpr _ f args fs = //todo: fieldselectors
234 lookup f >>= \expected ->
235 mapM infer args >>= \argTypes
237 IntExpr _ _ = pure $ (zero, IntType)
238 BoolExpr _ _ = pure $ (zero, BoolType)
239 CharExpr _ _ = pure $ (zero, CharType)
242 op2Type :: Op2 -> Typing Type
244 | elem op [BiPlus, BiMinus, BiTimes, BiDivide, BiMod]
245 = pure (IntType ->> IntType ->> IntType)
246 | elem op [BiEquals, BiUnEqual]
247 = fresh >>= \t1-> fresh >>= \t2-> pure (t1 ->> t2 ->> BoolType)
248 | elem op [BiLesser, BiGreater, BiLesserEq, BiGreaterEq]
249 = pure (IntType ->> IntType ->> BoolType)
250 | elem op [BiAnd, BiOr]
251 = pure (BoolType ->> BoolType ->> BoolType)
253 = fresh >>= \t1-> pure (t1 ->> ListType t1 ->> ListType t1)
255 op1Type :: Op1 -> Typing Type
256 op1Type UnNegation = pure $ (BoolType ->> BoolType)
257 op1Type UnMinus = pure $ (IntType ->> IntType)
260 Mapmap :: (a->b) ('Map'.Map k a) -> ('Map'.Map k b)
261 Mapmap _ 'Map'.Tip = 'Map'.Tip
262 Mapmap f ('Map'.Bin sz k v ml mr) = 'Map'.Bin sz k (f v)
266 instance toString Scheme where
267 toString (Forall x t) =
268 concat ["Forall ": map ((+++) "\n") x] +++ toString t
270 instance toString Gamma where
272 concat [concat [k, ": ", toString v, "\n"]\\(k, v)<-'Map'.toList mp]
274 instance toString SemError where
275 toString (SanityError p e) = concat [toString p,
276 "SemError: SanityError: ", e]
277 toString se = "SemError: "
279 instance MonadTrans (StateT (Gamma, [TVar])) where
280 liftT m = StateT \s-> m >>= \a-> return (a, s)
282 //// ------------------------
283 //// First step: Inference
284 //// ------------------------//
286 //unify :: Type Type -> Infer ()
287 //unify t1 t2 = tell [(t1, t2)]//
289 //fresh :: Infer Type
290 //fresh = (gets id) >>= \vars-> (put $ tail vars) >>| (pure $ IdType $ head vars)//
292 //op2Type :: Op2 -> Infer Type
294 //| elem op [BiPlus, BiMinus, BiTimes, BiDivide, BiMod]
295 // = pure (IntType ->> IntType ->> IntType)
296 //| elem op [BiEquals, BiUnEqual]
297 // = fresh >>= \t1-> fresh >>= \t2-> pure (t1 ->> t2 ->> BoolType)
298 //| elem op [BiLesser, BiGreater, BiLesserEq, BiGreaterEq]
299 // = pure (IntType ->> IntType ->> BoolType)
300 //| elem op [BiAnd, BiOr]
301 // = pure (BoolType ->> BoolType ->> BoolType)
303 // = fresh >>= \t1-> pure (t1 ->> ListType t1 ->> ListType t1)//
305 //op1Type :: Op1 -> Infer Type
306 //op1Type UnNegation = pure $ (BoolType ->> BoolType)
307 //op1Type UnMinus = pure $ (IntType ->> IntType)//
309 ////instantiate :: Scheme -> Infer Type
310 ////instantiate (Forall as t) = mapM (const fresh) as//
312 //lookupEnv :: String -> Infer Type
313 //lookupEnv ident = asks ('Map'.get ident)
315 // Nothing = liftT $ Left $ UndeclaredVariableError zero ident
316 // Just (Forall as t) = pure t //instantiate ???//
318 //class infer a :: a -> Infer Type
319 //instance infer Expr where
320 // infer (VarExpr _ (VarDef ident fs)) = lookupEnv ident
321 // infer (Op2Expr _ e1 op e2) =
322 // infer e1 >>= \t1 ->
323 // infer e2 >>= \t2 ->
324 // fresh >>= \frsh ->
325 // let given = t1 ->> (t2 ->> frsh) in
326 // op2Type op >>= \expected ->
327 // unify expected given >>|
329 // infer (Op1Expr _ op e) =
330 // infer e >>= \t1 ->
331 // fresh >>= \frsh ->
332 // let given = t1 ->> frsh in
333 // op1Type op >>= \expected ->
334 // unify expected given >>|
336 // infer (IntExpr _ _) = pure IntType
337 // infer (CharExpr _ _) = pure CharType
338 // infer (BoolExpr _ _) = pure BoolType
339 // infer (FunExpr _ f args sels) = //todo, iets met field selectors
340 // lookupEnv f >>= \expected ->
341 // fresh >>= \frsh ->
342 // mapM infer args >>= \argTypes ->
343 // let given = foldr (->>) frsh argTypes in
344 // unify expected given >>|
346 // infer (EmptyListExpr _) = ListType <$> fresh
347 // infer (TupleExpr _ (e1, e2)) =
348 // infer e1 >>= \et1->infer e2 >>= \et2->pure $ TupleType (et1, et2)//
350 ////:: VarDef = VarDef String [FieldSelector]
351 ////:: FieldSelector = FieldHd | FieldTl | FieldFst | FieldSnd
352 ////:: Op1 = UnNegation | UnMinus
353 ////:: Op2 = BiPlus | BiMinus | BiTimes | BiDivide | BiMod | BiEquals | BiLesser |
354 //// BiGreater | BiLesserEq | BiGreaterEq | BiUnEqual | BiAnd | BiOr | BiCons
355 ////:: FunDecl = FunDecl Pos String [String] (Maybe Type) [VarDecl] [Stmt]
356 ////:: FunCall = FunCall String [Expr]
358 //// = IfStmt Expr [Stmt] [Stmt]
359 //// | WhileStmt Expr [Stmt]
360 //// | AssStmt VarDef Expr
361 //// | FunStmt FunCall
362 //// | ReturnStmt (Maybe Expr)
363 ////:: Pos = {line :: Int, col :: Int}
364 ////:: AST = AST [VarDecl] [FunDecl]
365 ////:: VarDecl = VarDecl Pos Type String Expr
367 //// = TupleType (Type, Type)
375 //// | (->>) infixl 7 Type Type