protected override void Visit(MultiplyExpression expr)
{
Console.Write("(");
Visit(expr.Left);
Console.Write(" * ");
Visit(expr.Right);
Console.Write(")");
}
protected override void Visit(MultiplyExpression expr)
{
Visit(expr.Left);
Visit(expr.Right);
var right = Stack.Pop();
var left = Stack.Pop();
Stack.Push(left * right);
}
protected abstract void Visit(MultiplyExpression expr);
