public void Visit(AssignmentStmt node) { try { string name = node.Children [0].Name; if (!SymbolTable.ContainsKey (name)) { throw new SemanticError ("Variable " + name + " needs to be declared before use", node.Children [0].Row, node.Children [0].Column); } // check if the assigned expression is of the same type as the variable in symbol table VisitChildren (node.Children [1]); string type = TypeStack.Pop (); if (type != SymbolTable [name].Type) { throw new SemanticError ("Variable " + name + " of type " + SymbolTable [name].Type + " can not be assigned a value of type " + type, node.Children [0].Row, node.Children [0].Column); } } catch (SemanticError error) { Errors.Add (error); TypeStack.Clear (); } }
public void Visit(AssignmentStmt node) { string name = node.Children [0].Name; // visit the children, the value should be on top of the stack after that VisitChildren (node.Children [1]); StackValue stackValue = ValueStack.Pop (); // update the value in symbol table SymbolTable [name].Value = stackValue.Value; }
private Statement Stmt() { switch ((Token.Types)currentToken.Type) { case Token.Types.Var: VarDeclStmt varDeclStmt = new VarDeclStmt ("VarDecl", currentToken.Row, currentToken.Column); Match (Token.Types.Var); varDeclStmt.AddChild (IdentifierNameStmt ()); Match (Token.Types.Colon); varDeclStmt.AddChild (Type ()); if ((Token.Types)currentToken.Type == Token.Types.Assign) { Match (Token.Types.Assign); varDeclStmt.AddChild (Expr ()); return varDeclStmt; } else if ((Token.Types)currentToken.Type == Token.Types.Semicolon) { return varDeclStmt; } throw new SyntaxError ("Expected Assign, got: " + currentToken.Type, currentToken.Row, currentToken.Column); case Token.Types.Identifier: AssignmentStmt assignmentStmt = new AssignmentStmt ("AssignmentStmt", currentToken.Row, currentToken.Column); assignmentStmt.AddChild (IdentifierNameStmt ()); Match (Token.Types.Assign); assignmentStmt.AddChild (Expr ()); return assignmentStmt; case Token.Types.For: ForStmt forStmt = new ForStmt ("ForStmt", currentToken.Row, currentToken.Column); Match (Token.Types.For); forStmt.AddChild (IdentifierNameStmt ()); Match (Token.Types.In); forStmt.AddChild (Expr ()); Match (Token.Types.Range); forStmt.AddChild (Expr ()); Match (Token.Types.Do); forStmt.AddChild (Stmts ()); Match (Token.Types.End); Match (Token.Types.For); return forStmt; case Token.Types.Read: ReadStmt readStmt = new ReadStmt ("ReadStmt", currentToken.Row, currentToken.Column); Match (Token.Types.Read); readStmt.AddChild (IdentifierNameStmt ()); return readStmt; case Token.Types.Print: PrintStmt printStmt = new PrintStmt ("PrintStmt", currentToken.Row, currentToken.Column); Match (Token.Types.Print); printStmt.AddChild (Expr ()); return printStmt; case Token.Types.Assert: AssertStmt assertStmt = new AssertStmt ("AssertStmt", currentToken.Row, currentToken.Column); Match (Token.Types.Assert); Match (Token.Types.LeftParenthesis); assertStmt.AddChild (Expr ()); Match (Token.Types.RightParenthesis); return assertStmt; default: throw new SyntaxError ("invalid start symbol for statement " + currentToken.Lexeme, currentToken.Row, currentToken.Column); } }