本程序主要的功能是利用链表将用户输入的任意精度中缀表达式转换成后缀表达式，为了以便于区分数据和操作符，数据间用下划线将它们区分开来，并且计算出此表达式的值。 2．需要注意的是：此程序所叙述的四则运算是狭义的，并没有显式的要求用户以中括弧“[]”或者是大括弧“{}”进行输入,因为这样会大大的加大程序的代码量，为了简便起见，同时又为了实现四则混合运算的功能，只要用户将含有中括弧或者是大括弧的地方均以小括弧表示即可。-The main function of this program is to use the list to the user to enter an arbitrary precision infix expression into postfix expression, in order to distinguish between data and operators, the data underscore between them separate, and this expression is calculated values. 2. Note that: This procedure is described in four arithmetic narrow and did not require the user to explicitly in brackets " []"　or braces " {}"　for input, as this will greatly increase the program the amount of code, for simplicity, and in order to achieve four mixed computing capabilities, as long as the user will contain the brackets or braces are in parentheses indicate the place can be.