演示用算符优先法对算术表达式求值的过程。



(1)从键盘输入任意一个语法正确的（中缀）表达式，显示并保存该表达式。

(2)利用栈结构，把上述（中缀）表达式转换成后缀表达式，并显示栈的状态变化过程和所得到的后缀表达式。

(3)利用栈结构，对上述后缀表达式进行求值，并显示栈的状态变化过程和最终结果。

-Demonstration by operator precedence for arithmetic expression evaluation process. (1) from the keyboard input any grammatically correct (infix) expression, display and save the expression. (2) use of the stack structure, the (infix) expression into a postfix expression and display the stack status change process and the postfix expression. (3) the use of stack structure, the postfix expression is evaluated, and display the stack status change process and the final result.