以字符序列的形式从键盘输入语法正确的，不含变量的整型表达式。利用算符优先关系，实现对算术四则混合运算表达式的求值，并在求值中运算符栈、运算数栈、输入字符和主要操作的变化过程-In the form of a sequence of characters from the keyboard input syntax is correct, excluding the variable of integer expressions. Change operator precedence relations, four hybrid operation of the arithmetic expression is evaluated, and evaluation in the operator stack, operand stack, the input character and the main operation