+from parse import :: ParserOutput, :: Error
+
+:: Gamma :== ('Map'.Map String Type, [String])
+:: Env a :== StateT Gamma (Either SemError) a
+//StateT (Gamma -> Either SemError (a, Gamma))
+
+//we need to redefine this even though it is in Control.Monad.State
+instance MonadTrans (StateT Gamma) where
+ liftT m = StateT \s-> m >>= \a-> return (a, s)
+
+get = gets id
+
+sem :: AST -> SemOutput
+sem (AST vd fd) = case runStateT m ('Map'.newMap, getRandomStream 1) of
+ Left e = Left [e]
+ Right ((vds, fds), gamma) = Right ((AST vds fds), gamma)
+where
+ m :: Env ([VarDecl], [FunDecl])
+ m = mapM semVarDecl vd >>= \vds ->
+ mapM semFunDecl fd >>= \fds ->
+ pure (vds, fds)
+
+semFunDecl :: FunDecl -> Env FunDecl
+semFunDecl fd=:(FunDecl p f args mt vds stmts) =
+ saveGamma >>= \gamma ->
+ (case mt of
+ Nothing = let t = IdType f in putIdent f t >>| pure t
+ Just t = putIdent f t >>| pure t) >>= \ft ->
+ mapM_ (\a-> freshIdent >>= \fr-> putIdent a (IdType fr)) args >>|
+ mapM_ semVarDecl vds >>|
+ mapM_ (checkStmt $ resultType ft) stmts >>|
+ restoreGamma gamma >>| pure fd
+
+semVarDecl :: VarDecl -> Env VarDecl
+semVarDecl (VarDecl pos type ident ex) = unify type ex
+ >>= \t-> putIdent ident t >>| (pure $ VarDecl pos t ident ex)
+
+checkStmt ::Type Stmt -> Env Stmt
+checkStmt t (IfStmt c st se) = unify BoolType c >>| mapM (checkStmt t) st
+ >>= \st1-> mapM (checkStmt t) se >>= \se1-> pure (IfStmt c st1 se1)
+checkStmt t w=:(WhileStmt c et) = unify BoolType c >>| mapM (checkStmt t) et
+ >>= \et1-> pure w
+checkStmt t (AssStmt (VarDef ident fs) e) = undef
+checkStmt t r=:(FunStmt (FunCall f es)) = typeFun f es >>| pure r
+checkStmt VoidType r=:(ReturnStmt Nothing) = pure r
+checkStmt t r=:(ReturnStmt (Just e)) = unify t e >>| pure r
+
+typeExpr :: Expr -> Env Type
+typeExpr (IntExpr _ _) = pure IntType
+typeExpr (CharExpr _ _) = pure CharType
+typeExpr (BoolExpr _ _) = pure BoolType
+typeExpr (Op1Expr p UnNegation expr) = unify BoolType expr
+typeExpr (Op1Expr p UnMinus expr) = unify IntType expr
+typeExpr (TupleExpr p (e1, e2)) = typeExpr e1
+ >>= \t1-> typeExpr e2 >>= \t2-> pure $ TupleType (t1, t2)
+typeExpr (Op2Expr p e1 op e2)
+| isMember op [BiPlus, BiMinus, BiTimes, BiDivide, BiMod] =
+ typeOp2 e1 e2 op [IntType] IntType
+| isMember op [BiEquals, BiUnEqual] =
+ typeOp2 e1 e2 op [IntType, BoolType, CharType] BoolType
+| isMember op [BiLesser, BiGreater, BiLesserEq, BiGreaterEq] =
+ typeOp2 e1 e2 op [IntType, CharType] BoolType
+| isMember op [BiAnd, BiOr] =
+ typeOp2 e1 e2 op [BoolType] BoolType
+| op == BiCons = typeExpr e1 >>= \t1-> typeExpr e2
+ >>= \t2-> unify (ListType t1) t2
+typeExpr (EmptyListExpr p) = freshIdent >>= \frsh-> let t = IdType frsh in
+ putIdent frsh t >>| pure t
+typeExpr (FunExpr p (FunCall f es)) = typeFun f es
+typeExpr (VarExpr p (VarDef ident fs)) = gets (\(st, r)->'Map'.get ident st)
+ >>= \mt->case mt of
+ Nothing = liftT $ Left $ UndeclaredVariableError p ident
+ Just t = unify t fs
+
+typeOp2 :: Expr Expr Op2 [Type] Type -> Env Type
+typeOp2 e1 e2 op ts ret = typeExpr e1 >>= \t1-> typeExpr e2 >>= \t2->
+ unify t1 t2 >>= \t3->if (isMember t3 ts) (pure ret)
+ (liftT $ Left $ OperatorError (extrPos e1) op t3)
+
+buildFunctionType :: String [Expr] -> Env Type
+buildFunctionType frsh [] = let t = IdType frsh in putIdent frsh t >>| pure t
+buildFunctionType frsh [e:es] = (->>) <$> typeExpr e <*> buildFunctionType frsh es
+
+unifyApp :: Type [Expr] -> Env Type
+unifyApp t [] = pure t
+unifyApp (tf1 ->> tf2) [t1:ts] = unify tf1 t1 >>| unifyApp tf2 ts
+unifyApp t1 t2 = liftT $ Left $ UnifyError zero t1 (IdType "[expressions, FIXME]")
+
+typeFun :: String [Expr] -> Env Type
+typeFun f es = gets (\(st, r)->'Map'.get f st) >>= \mt-> case mt of
+ Nothing = freshIdent >>= \frsh-> buildFunctionType frsh es
+ >>= \ft-> putIdent f ft >>| (pure $ IdType frsh)
+ Just t = unifyApp t es
+
+resultType :: Type -> Type
+resultType (_ ->> t) = resultType t
+resultType t = t
+
+class unify a :: Type a -> Env Type
+
+instance unify [FieldSelector] where
+ unify t [] = pure t
+ unify (ListType t) [FieldHd:fs] = unify t fs
+ unify t=:(ListType _) [FieldTl:fs] = unify t fs
+ unify (TupleType (t, _)) [FieldFst:fs] = unify t fs
+ unify (TupleType (_, t)) [FieldSnd:fs] = unify t fs
+ unify t [fs:_] = liftT $ Left $ FieldSelectorError zero t fs
+
+instance unify Expr where
+ unify (_ ->> _) e = liftT $ Left $ ParseError (extrPos e)
+ "Expression cannot be a higher order function. Yet..."
+ unify VoidType e = liftT $ Left $ ParseError (extrPos e)
+ "Expression cannot be a Void type."
+ unify (IdType _) e = liftT $ Left $ ParseError (extrPos e)
+ "Expression cannot be an polymorf type."
+ unify VarType e = typeExpr e
+ //we have to cheat to decorate the error, can be done nicer?
+ unify t e = StateT $ \s0 -> let res = runStateT m s0 in case res of
+ Left err = Left $ decErr e err
+ Right t = Right t //note, t :: (Type, Gamma)
+ where m = typeExpr e >>= \tex-> unify t tex
+
+instance unify Type where
+ unify IntType IntType = pure IntType
+ unify BoolType BoolType = pure BoolType
+ unify CharType CharType = pure CharType
+ unify (IdType i) t=:(IdType j) = replace i t >>| pure t
+ unify t (IdType i) = unify (IdType i) t
+ unify (IdType i) t = replace i t >>| pure t
+ unify (ListType t1) (ListType t2) = unify t1 t2 >>| (pure $ ListType t1)
+ unify (ta1 ->> ta2) (tb1 ->> tb2) = unify ta1 tb1 >>= \ta-> unify ta2 tb2
+ >>= \tb-> pure (ta ->> tb)
+ unify t1 t2 = liftT $ Left $ UnifyError zero t1 t2
+
+instance zero Pos where
+ zero = {line=0,col=0}
+
+decErr :: Expr SemError -> SemError
+decErr e (UnifyError _ t1 t2) = UnifyError (extrPos e) t1 t2
+decErr e (FieldSelectorError _ t fs) = FieldSelectorError (extrPos e) t fs
+decErr e (ParseError _ s) = ParseError (extrPos e) s
+decErr e err = err
+
+dc2 :: Expr (Either SemError a) -> Either SemError a
+dc2 e (Right t) = Right t
+dc2 e (Left err) = Left err
+
+extrPos :: Expr -> Pos
+extrPos (VarExpr p _) = p
+extrPos (Op2Expr p _ _ _) = p
+extrPos (Op1Expr p _ _) = p
+extrPos (IntExpr p _) = p
+extrPos (CharExpr p _) = p
+extrPos (BoolExpr p _) = p
+extrPos (FunExpr p _) = p
+extrPos (EmptyListExpr p) = p
+extrPos (TupleExpr p _) = p
+
+instance toString Gamma where
+ toString (mp, _) = concat
+ [concat [k, ": ", toString v, "\n"]\\(k, v) <- 'Map'.toList mp]
+
+getRandomStream :: Int -> [String]
+getRandomStream i = genIdents $ filter (isAlpha o toChar) (genRandInt i)
+ where
+ genIdents r = let (ic, r2) = splitAt 5 r in [toString ic: genIdents r2]
+
+freshIdent :: Env String
+freshIdent = get >>= \(st, [ident:rest])-> put (st, rest)
+ >>| case 'Map'.get ident st of
+ Nothing = pure ident
+ _ = freshIdent