public override void Visit(AdditionExpression ae)
 {
     sb.Append("(");
     ae.LHS.Accept(this);
     sb.Append("+");
     ae.RHS.Accept(this);
     sb.Append(")");
 }
        static void Main(string[] args)
        {
            var simple = new AdditionExpression(new Value(2), new MultiplicationExpression(new Value(4), new Value(8)));
            var ep     = new ExpressionPrinter();

            ep.Visit(simple);
            Console.WriteLine(ep);
        }
 public abstract void Visit(AdditionExpression ae);