Working on inference for statements

diff --git a/sem.icl b/sem.icl
index fa4b3ae..8ed05eb 100644 (file)
--- a/sem.icl
+++ b/sem.icl
@@ -128,13 +128,16 @@ instance Typeable Gamma where
     ftv gamma       = concatMap id $ map ftv ('Map'.elems gamma)
     subst s gamma   = Mapmap (subst s) gamma
 
+extend :: String Scheme Gamma -> Gamma
+extend k t g = 'Map'.put k t g
+
 //// ------------------------
 //// algorithm U, Unification 
 //// ------------------------
 instance zero Substitution where zero = 'Map'.newMap
 
 compose :: Substitution Substitution -> Substitution
-compose s1 s2 = 'Map'.union (Mapmap (subst s2) s1) s2
+compose s1 s2 = 'Map'.union (Mapmap (subst s1) s2) s1
 //Note: just like function compositon compose does snd first
 
 occurs :: TVar a -> Bool | Typeable a
@@ -164,8 +167,8 @@ gamma :: Typing Gamma
 gamma = gets fst
 putGamma :: Gamma -> Typing ()
 putGamma g = modify (appFst $ const g) >>| pure ()
-changeGamma :: (Gamma -> Gamma) -> Typing ()
-changeGamma f = modify (appFst f) >>| pure ()
+changeGamma :: (Gamma -> Gamma) -> Typing Gamma
+changeGamma f = modify (appFst f) >>| gamma
 withGamma :: (Gamma -> a) -> Typing a
 withGamma f = f <$> gamma
 fresh :: Typing Type
@@ -190,19 +193,21 @@ instantiate (Forall bound t) =
 generalize :: Type -> Typing Scheme
 generalize t = gamma >>= \g-> pure $ Forall (difference (ftv t) (ftv g)) t
 
-lookup :: String -> Typing Scheme 
+lookup :: String -> Typing Type 
 lookup k = gamma >>= \g-> case 'Map'.member k g of
     False = liftT (Left $ UndeclaredVariableError zero k)
-    True = pure ('Map'.find k g)
+    True = instantiate $ 'Map'.find k g
 
 //The inference class
 //When tying it all together we will treat the program is a big 
 //let x=e1 in let y=e2 in .... 
 class infer a :: a -> Typing (Substitution, Type)
 
+////---- Inference for Expressions ----
+
 instance infer Expr where 
  infer e = case e of
-    VarExpr _ (VarDef k fs) = (\t->(zero,t)) <$> (lookup k >>= instantiate)
+    VarExpr _ (VarDef k fs) = (\t->(zero,t)) <$> lookup k
     //instantiate is key for the let polymorphism!
     //TODO: field selectors
 
@@ -213,7 +218,7 @@ instance infer Expr where
         let given = t1 ->> t2 ->> tv in 
         op2Type op >>= \expected ->
         lift (unify expected given) >>= \s3 ->
-        pure ((compose s1 $ compose s2 s3), subst s3 tv)
+        pure ((compose s3 $ compose s2 s1), subst s3 tv)
 
     Op1Expr _ op e1 =
         infer e1 >>= \(s1, t1) -> 
@@ -221,23 +226,23 @@ instance infer Expr where
         let given = t1 ->> tv in 
         op1Type op >>= \expected ->
         lift (unify expected given) >>= \s2 ->
-        pure (compose s1 s2, subst s2 tv)
+        pure (compose s2 s1, subst s2 tv)
 
     EmptyListExpr _ = (\tv->(zero,tv)) <$> fresh
 
     TupleExpr _ (e1, e2) = 
         infer e1 >>= \(s1, t1) -> 
         infer e2 >>= \(s2, t2) ->
-        pure (compose s1 s2, TupleType (t1,t2))
+        pure (compose s2 s1, TupleType (t1,t2))
 
     FunExpr _ f args fs = //todo: fieldselectors
-        lookup f >>= instantiate >>= \expected ->
-        let accTypSub = (\(s,ts) e->infer e >>= \(s_,et)->pure (compose s_ s,ts++[et])) in
-        foldM accTypSub (zero,[]) args >>= \(s1, argTs)->
+        lookup f >>= \expected ->
+        let accST = (\(s,ts) e->infer e >>= \(s_,et)->pure (compose s_ s,ts++[et])) in
+        foldM accST (zero,[]) args >>= \(s1, argTs)->
         fresh >>= \tv->
         let given = foldr (->>) tv argTs in
         lift (unify expected given) >>= \s2->
-        pure (compose s1 s2, subst s2 tv)
+        pure (compose s2 s1, subst s2 tv)
 
     IntExpr _ _ = pure $ (zero, IntType)
     BoolExpr _ _ = pure $ (zero, BoolType)
@@ -261,6 +266,39 @@ op1Type :: Op1 -> Typing Type
 op1Type UnNegation = pure $ (BoolType ->> BoolType)
 op1Type UnMinus = pure $ (IntType ->> IntType)
 
+////----- Inference for Statements -----
+applySubst :: Substitution -> Typing Gamma
+applySubst s = changeGamma (subst s)
+
+instance infer Stmt where
+ infer s = case s of
+    IfStmt e th el = 
+        infer e >>= \(s1, et)->
+        lift (unify et BoolType) >>= \s2 ->
+        applySubst (compose s2 s1) >>|        
+        infer th >>= \(s3, tht)->
+        applySubst s3 >>|
+        infer el >>= \(s4, elt)->
+        applySubst s4 >>|
+        lift (unify tht elt) >>= \s5-> 
+        pure (compose s5 $ compose s4 $ compose s3 $ compose s1 s2, subst s5 tht)
+
+    WhileStmt e wh = 
+        infer e >>= \(s1, et)->
+        lift (unify et BoolType) >>= \s2 ->
+        applySubst (compose s2 s1) >>|
+        infer wh >>= \(s3, wht)->
+        pure (compose s3 $ compose s1 s2, subst s3 wht)
+
+    AssStmt (VarDef k fs) e =
+        infer e >>= \(s1, et)->
+        applySubst s1 >>|
+        changeGamma (extend k (Forall [] et)) >>| //todo: fieldselectors
+        pure (s1, VoidType)
+
+
+instance infer [a] | infer a where
+    infer _ = undef
 
 Mapmap :: (a->b) ('Map'.Map k a) -> ('Map'.Map k b)
 Mapmap _ 'Map'.Tip = 'Map'.Tip