算术表达式求值：置操作数栈为空栈，表达式起始以#为栈底元素，依次读入每个字符，若是操作符则进入OPND栈，运算符则进入OPTR栈的栈定运算符比较优先权后作相应操作，直到OPTR栈顶元素和当前读入字符为-Arithmetic expression evaluation: set stack operand stack is empty, the expression starting with# as the bottom of the stack element, followed by re