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
29 :: Scheme = Forall [TVar] Type
30 :: Gamma :== 'Map'.Map String Scheme //map from Variables! to types
31 :: Typing a :== StateT (Gamma, [TVar]) (Either SemError) a
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 defaultGamma :: Gamma //includes all default functions
52 defaultGamma = extend "print" (Forall ["a"] ((IdType "a") ->> VoidType))
53 $ extend "isEmpty" (Forall ["a"] ((ListType (IdType "a")) ->> BoolType))
54 $ extend "read" (Forall [] (IntType ->> (ListType CharType)))
57 sem :: AST -> Either [SemError] AST
58 sem (AST fd) = case foldM (const $ hasNoDups fd) () fd
59 >>| foldM (const isNiceMain) () fd
61 >>| evalStateT (type fd) (defaultGamma, variableStream) of
63 Right (_,fds) = Right (AST fds)
65 hasNoDups :: [FunDecl] FunDecl -> Either SemError ()
66 hasNoDups fds (FunDecl p n _ _ _ _)
67 # mbs = map (\(FunDecl p` n` _ _ _ _)->if (n == n`) (Just p`) Nothing) fds
68 = case catMaybes mbs of
69 [] = Left $ SanityError p "HUH THIS SHOULDN'T HAPPEN"
71 [_:x] = Left $ SanityError p (concat
72 [n, " multiply defined at ", toString p])
74 hasMain :: [FunDecl] -> Either SemError ()
75 hasMain [(FunDecl _ "main" _ _ _ _):fd] = pure ()
76 hasMain [_:fd] = hasMain fd
77 hasMain [] = Left $ SanityError zero "no main function defined"
79 isNiceMain :: FunDecl -> Either SemError ()
80 isNiceMain (FunDecl p "main" as mt _ _) = case (as, mt) of
81 ([_:_], _) = Left $ SanityError p "main must have arity 0"
84 Just VoidType = pure ()
85 _ = Left $ SanityError p "main has to return Void")
86 isNiceMain _ = pure ()
88 class Typeable a where
90 subst :: Substitution a -> a
92 instance Typeable Scheme where
93 ftv (Forall bound t) = difference (ftv t) bound
94 subst s (Forall bound t) = Forall bound $ subst s_ t
95 where s_ = 'Map'.filterWithKey (\k _ -> not (elem k bound)) s
97 instance Typeable [a] | Typeable a where
98 ftv types = foldr (\t ts-> ftv t ++ ts) [] types
99 subst s ts = map (\t->subst s t) ts
101 instance Typeable Type where
102 ftv (TupleType (t1, t2)) = ftv t1 ++ ftv t2
103 ftv (ListType t) = ftv t
104 ftv (IdType tvar) = [tvar]
105 ftv (t1 ->> t2) = ftv t1 ++ ftv t2
107 subst s (TupleType (t1, t2))= TupleType (subst s t1, subst s t2)
108 subst s (ListType t1) = ListType (subst s t1)
109 subst s (t1 ->> t2) = (subst s t1) ->> (subst s t2)
110 subst s t1=:(IdType tvar) = 'Map'.findWithDefault t1 tvar s
113 instance Typeable Gamma where
114 ftv gamma = concatMap id $ map ftv ('Map'.elems gamma)
115 subst s gamma = Mapmap (subst s) gamma
117 extend :: String Scheme Gamma -> Gamma
118 extend k t g = 'Map'.put k t g
120 //// ------------------------
121 //// algorithm U, Unification
122 //// ------------------------
123 instance zero Substitution where zero = 'Map'.newMap
125 compose :: Substitution Substitution -> Substitution
126 compose s1 s2 = 'Map'.union (Mapmap (subst s1) s2) s1
127 //Note: just like function compositon compose does snd first
129 occurs :: TVar a -> Bool | Typeable a
130 occurs tvar a = elem tvar (ftv a)
132 unify :: Type Type -> Either SemError Substitution
133 unify t1 t2=:(IdType tv) | t1 == (IdType tv) = Right zero
134 | occurs tv t1 = Left $ InfiniteTypeError zero t1
135 | otherwise = Right $ 'Map'.singleton tv t1
136 unify t1=:(IdType tv) t2 = unify t2 t1
137 unify (ta1->>ta2) (tb1->>tb2) = unify ta1 tb1 >>= \s1->
138 unify ta2 tb2 >>= \s2->
139 Right $ compose s1 s2
140 unify (TupleType (ta1,ta2)) (TupleType (tb1,tb2)) = unify ta1 tb1 >>= \s1->
141 unify ta2 tb2 >>= \s2->
142 Right $ compose s1 s2
143 unify (ListType t1) (ListType t2) = unify t1 t2
144 unify t1 t2 | t1 == t2 = Right zero
145 | otherwise = Left $ UnifyError zero t1 t2
147 //// ------------------------
148 //// Algorithm M, Inference and Solving
149 //// ------------------------
150 gamma :: Typing Gamma
152 putGamma :: Gamma -> Typing ()
153 putGamma g = modify (appFst $ const g) >>| pure ()
154 changeGamma :: (Gamma -> Gamma) -> Typing Gamma
155 changeGamma f = modify (appFst f) >>| gamma
156 withGamma :: (Gamma -> a) -> Typing a
157 withGamma f = f <$> gamma
159 fresh = gets snd >>= \vars->
160 modify (appSnd $ const $ tail vars) >>|
161 pure (IdType (head vars))
163 lift :: (Either SemError a) -> Typing a
164 lift (Left e) = liftT $ Left e
165 lift (Right v) = pure v
167 //instantiate maps a schemes type variables to variables with fresh names
168 //and drops the quantification: i.e. forall a,b.a->[b] becomes c->[d]
169 instantiate :: Scheme -> Typing Type
170 instantiate (Forall bound t) =
171 mapM (const fresh) bound >>= \newVars->
172 let s = 'Map'.fromList (zip (bound,newVars)) in
175 //generalize quentifies all free type variables in a type which are not
177 generalize :: Type -> Typing Scheme
178 generalize t = gamma >>= \g-> pure $ Forall (difference (ftv t) (ftv g)) t
180 lookup :: String -> Typing Type
181 lookup k = gamma >>= \g-> case 'Map'.member k g of
182 False = liftT (Left $ UndeclaredVariableError zero k)
183 True = instantiate $ 'Map'.find k g
185 //The inference class
186 //When tying it all together we will treat the program is a big
187 //let x=e1 in let y=e2 in ....
188 class infer a :: a -> Typing (Substitution, Type)
190 ////---- Inference for Expressions ----
192 instance infer Expr where
194 VarExpr _ (VarDef k fs) = lookup k >>= \t ->
195 foldM foldFieldSelectors t fs >>= \finalT ->
199 infer e1 >>= \(s1, t1) ->
200 infer e2 >>= \(s2, t2) ->
202 let given = t1 ->> t2 ->> tv in
203 op2Type op >>= \expected ->
204 lift (unify expected given) >>= \s3 ->
205 pure ((compose s3 $ compose s2 s1), subst s3 tv)
208 infer e1 >>= \(s1, t1) ->
210 let given = t1 ->> tv in
211 op1Type op >>= \expected ->
212 lift (unify expected given) >>= \s2 ->
213 pure (compose s2 s1, subst s2 tv)
215 EmptyListExpr _ = (\tv->(zero,tv)) <$> fresh
217 TupleExpr _ (e1, e2) =
218 infer e1 >>= \(s1, t1) ->
219 infer e2 >>= \(s2, t2) ->
220 pure (compose s2 s1, TupleType (t1,t2))
222 FunExpr _ f args fs = //todo: fieldselectors
223 lookup f >>= \expected ->
224 let accST = (\(s,ts) e->infer e >>= \(s_,et)->pure (compose s_ s,ts++[et])) in
225 foldM accST (zero,[]) args >>= \(s1, argTs)->
227 let given = foldr (->>) tv argTs in
228 lift (unify expected given) >>= \s2->
229 let fReturnType = subst s2 tv in
230 foldM foldFieldSelectors fReturnType fs >>= \returnType ->
231 pure (compose s2 s1, returnType)
233 IntExpr _ _ = pure $ (zero, IntType)
234 BoolExpr _ _ = pure $ (zero, BoolType)
235 CharExpr _ _ = pure $ (zero, CharType)
237 foldFieldSelectors :: Type FieldSelector -> Typing Type
238 foldFieldSelectors (ListType t) (FieldHd) = pure t
239 foldFieldSelectors t=:(ListType _) (FieldTl) = pure t
240 foldFieldSelectors (TupleType (t1, _)) (FieldFst) = pure t1
241 foldFieldSelectors (TupleType (_, t2)) (FieldSnd) = pure t2
242 foldFieldSelectors t fs = liftT $ Left $ FieldSelectorError zero t fs
244 op2Type :: Op2 -> Typing Type
246 | elem op [BiPlus, BiMinus, BiTimes, BiDivide, BiMod]
247 = pure (IntType ->> IntType ->> IntType)
248 | elem op [BiEquals, BiUnEqual]
249 = fresh >>= \t1-> fresh >>= \t2-> pure (t1 ->> t2 ->> BoolType)
250 | elem op [BiLesser, BiGreater, BiLesserEq, BiGreaterEq]
251 = pure (IntType ->> IntType ->> BoolType)
252 | elem op [BiAnd, BiOr]
253 = pure (BoolType ->> BoolType ->> BoolType)
255 = fresh >>= \t1-> pure (t1 ->> ListType t1 ->> ListType t1)
257 op1Type :: Op1 -> Typing Type
258 op1Type UnNegation = pure $ (BoolType ->> BoolType)
259 op1Type UnMinus = pure $ (IntType ->> IntType)
261 ////----- Inference for Statements -----
262 applySubst :: Substitution -> Typing Gamma
263 applySubst s = changeGamma (subst s)
265 instance infer Stmt where
268 infer e >>= \(s1, et)->
269 lift (unify et BoolType) >>= \s2 ->
270 applySubst (compose s2 s1) >>|
271 infer th >>= \(s3, tht)->
273 infer el >>= \(s4, elt)->
275 lift (unify tht elt) >>= \s5->
276 pure (compose s5 $ compose s4 $ compose s3 $ compose s2 s1, subst s5 tht)
279 infer e >>= \(s1, et)->
280 lift (unify et BoolType) >>= \s2 ->
281 applySubst (compose s2 s1) >>|
282 infer wh >>= \(s3, wht)->
283 pure (compose s3 $ compose s2 s1, subst s3 wht)
285 AssStmt (VarDef k fs) e =
286 lookup k >>= \expected ->
287 infer e >>= \(s1, given)->
288 foldM reverseFs given (reverse fs) >>= \varType->
289 lift (unify expected varType) >>= \s2->
290 let s = compose s2 s1 in
292 changeGamma (extend k (Forall [] (subst s varType))) >>|
295 FunStmt f es _ = pure (zero, VoidType)
297 ReturnStmt Nothing = pure (zero, VoidType)
298 ReturnStmt (Just e) = infer e
300 reverseFs :: Type FieldSelector -> Typing Type
301 reverseFs t FieldHd = pure $ ListType t
302 reverseFs t FieldTl = pure $ ListType t
303 reverseFs t FieldFst = fresh >>= \tv -> pure $ TupleType (t, tv)
304 reverseFs t FieldSnd = fresh >>= \tv -> pure $ TupleType (tv, t)
306 //The type of a list of statements is either an encountered
307 //return, or VoidType
308 instance infer [a] | infer a where
309 infer [] = pure (zero, VoidType)
311 infer stmt >>= \(s1, t1) ->
313 infer ss >>= \(s2, t2) ->
316 VoidType = pure (compose s2 s1, t2)
318 VoidType = pure (compose s2 s1, t1)
319 _ = lift (unify t1 t2) >>= \s3 ->
320 pure (compose s3 $ compose s2 s1, t1)
322 //the type class inferes the type of an AST element (VarDecl or FunDecl)
323 //and adds it to the AST element
324 class type a :: a -> Typing (Substitution, a)
326 instance type VarDecl where
327 type (VarDecl p expected k e) =
328 infer e >>= \(s1, given) ->
332 Just expected_ = lift (unify expected_ given)
335 let vtype = subst (compose s2 s1) given in
336 generalize vtype >>= \t ->
337 changeGamma (extend k t) >>|
338 pure (compose s2 s1, VarDecl p (Just vtype) k e)
340 instance type FunDecl where
341 type (FunDecl p f args expected vds stmts) =
342 gamma >>= \outerScope-> //functions are infered in their own scopde
344 mapM introduce args >>= \argTs->
345 type vds >>= \(s1, tVds)->
347 infer stmts >>= \(s2, result)->
349 let argTs_ = map (subst $ compose s2 s1) argTs in
350 //abort (concat $ intersperse "\n" $ map toString argTs_) >>|
351 let given = foldr (->>) result argTs_ in
354 Just expected_ = lift (unify expected_ given))
356 let ftype = subst (compose s3 $ compose s2 s1) given in
357 generalize ftype >>= \t->
358 putGamma outerScope >>|
359 changeGamma (extend f t) >>|
360 pure (compose s3 $ compose s2 s1, FunDecl p f args (Just ftype) tVds stmts)
362 instance type [a] | type a where
363 type [] = pure (zero, [])
365 type v >>= \(s1, v_)->
367 type vs >>= \(s2, vs_)->
368 applySubst (compose s2 s1) >>|
369 pure (compose s2 s1, [v_:vs_])
371 introduce :: String -> Typing Type
374 changeGamma (extend k (Forall [] tv)) >>|
377 instance toString Scheme where
378 toString (Forall x t) =
379 concat ["Forall ": intersperse "," x] +++ concat [". ", toString t];
381 instance toString Gamma where
383 concat [concat [k, ": ", toString v, "\n"]\\(k, v)<-'Map'.toList mp]
385 instance toString Substitution where
387 concat [concat [k, ": ", toString t, "\n"]\\(k, t)<-'Map'.toList subs]
389 instance toString SemError where
390 toString (SanityError p e) = concat [toString p,
391 "SemError: SanityError: ", e]
392 toString (ParseError p s) = concat [toString p,
394 toString (UnifyError p t1 t2) = concat [toString p,
395 "Can not unify types, expected|given:\n", toString t1,
397 toString (InfiniteTypeError p t) = concat [toString p,
398 "Infinite type: ", toString t]
399 toString (FieldSelectorError p t fs) = concat [toString p,
400 "Can not run fieldselector '", toString fs, "' on type: ",
402 toString (OperatorError p op t) = concat [toString p,
403 "Operator error, operator '", toString op, "' can not be",
404 "used on type: ", toString t]
405 toString (UndeclaredVariableError p k) = concat [toString p,
406 "Undeclared identifier: ", k]
407 toString (ArgumentMisMatchError p str) = concat [toString p,
408 "Argument mismatch: ", str]
409 toString (Error e) = concat ["Unknown error during semantical",
412 instance toString (Maybe a) | toString a where
413 toString Nothing = "Nothing"
414 toString (Just e) = concat ["Just ", toString e]
416 instance MonadTrans (StateT (Gamma, [TVar])) where
417 liftT m = StateT \s-> m >>= \a-> return (a, s)
419 Mapmap :: (a->b) ('Map'.Map k a) -> ('Map'.Map k b)
420 Mapmap _ 'Map'.Tip = 'Map'.Tip
421 Mapmap f ('Map'.Bin sz k v ml mr) = 'Map'.Bin sz k (f v)