#include <stdio.h> #include<string.h> int main() { double a,b;//float精度不太够,double可以 char ch; scanf("%lf%c%lf",&a,&ch,&b); if(ch=='+') printf("%.4lf+%.4lf=%.4lf",a,b,a+b); else if(ch=='-') printf("%.4lf-%.4lf=%.4lf",a,b,a-b); else if(ch=='*') prin...