#include<stdio.h> int main() { double a,b;//最初用float,通过率90% char o; while(scanf("%lf%c%lf",&a,&o,&b)!=EOF) { switch(o) { case '+':printf("%.4f+%.4f=%.4f\n",a,b,a+b);break; case '-':printf("%.4f-%.4f=%.4f\n",a,b,a-b);break; ...