8、对中缀表达式(如(2+3.25)*4=)求组，读入表达式的各项滤去空格，直到读入"="，处理过程中若发生错误，则输出相应的错误信息，读入结束后，计算表达式中的各项，打印表达式的结果-8, the infix expression (such as (2+ 3.25)* 4 =) for group, read into the expression of the least squares spaces, until the read