//Console.WriteLine("begin to depthfist travel:");
while(tmpIEnum.MoveNext())
{
Console.WriteLine(tmpIEnum.Current.ToString());
}
}
public static void ShowStack_RPNCalCulator()
{
//read a expression string and push every character into the stack in queue.
Console.WriteLine("this is performance for stack,you can input a string like this '123*+',then this subprogramme can compute it and get the result '7',this is RPN calculator. ");
Console.WriteLine("please input a expression string:");