c语言 四则运算。给你一个简单的四则运算表达式，包含两个实数和一个运算符，请编程计算出结果。

楼主好~（保留两位小数）
main()
{
double a,b;char x;
printf("input:\n");
scanf("%lf%c%lf",&a,&x,&b);
switch(x)
{
case '+': printf("%.2lf\n",a+b); break;
case '-': printf("%.2lf\n",a-b); break;
case '*': printf("%.2lf\n",a*b); break;
case '/': printf("%.2lf\n",a/b); break;
default: printf("error\n");
}
}

#include "iostream.h"
#include "string.h"
#include "math.h"
int a,b;
char ch;

void input()
{
printf("please input :\n");
scanf("%lf%c%lf",&a,&ch,&b);
}
double MyFunction(double a,double b,char ch)
{
switch(ch)
{
case '+':
return a+b;
break;
case '-':
return a-b;
break;
case '*':
return a*b;
break;
case '/':
return a/b;
break;
default: printf("there are errors! please check the code carefully!\n");
}

void main()
{
input();
double result=MyFunction(a,b,ch);
printf("the result is%lf\n",result);
}