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 reading each character, if the operator is entering OPND stack, the operator is set to enter OPTR stack stack operation Fu made the remarks more priority to the corresponding operation until OPTR stack element and the current read characters