public void Print(AdditionExpression ae, StringBuilder sb)
{
sb.Append("(");
Print((dynamic)ae.Left, sb);
sb.Append("+");
Print((dynamic)ae.Right, sb);
sb.Append(")");
}
public static void Main()
{
var e = new AdditionExpression(
left: new DoubleExpression(1),
right: new AdditionExpression(
left: new DoubleExpression(2),
right: new DoubleExpression(3)));
var ep = new ExpressionPrinter();
var sb = new StringBuilder();
ep.Print((dynamic)e, sb);
Console.WriteLine(sb);
// disadvantages:
// 1) Performance penalty
// 2) Runtime error on missing visitor
// 3) Problematic w.r.t. inheritance
}