#include <stdio.h> int main(void) { double num1 = 0.0, num2 = 0.0;//float精度不够 char ch = '0'; scanf("%lf %c %lf", &num1, &ch, &num2); if (ch == '+' || ch == '-' || ch == '*' || ch == '/') { if (ch == '+') { printf("%.4lf+%.4lf=%.4lf", num1, num2, num1+num2); } if (ch =...