最近在学习c语言指针部分，用到指针函数，写了如下程序，运行有错误。但我明明觉得不错哇！望高手赐教！！
#include <stdio.h>


void main()
{
    double add(double,double);    //declare add,sub,mul,div functions
    double sub(double,double);
    double mul(double,double);
    double div(double,double);
   
    double (*oper_fun[])(double,double)={add,sub,mul,div};

    while(1)
    {   
        double a,b,c;
        printf("This is a simple calculator,it has 5 functions as follows!\n");
        printf("1.add\t2.sub\t3.mul\t4.div\t");
        printf("Please enter as such format:number number operation\n");
        scanf("%f%f%d",&a,&b,&c);
        printf("Result is:%f\n",oper_fun[ c - 1](a,b));
    }


}

    double add(double x,double y)    //add function
    {return x+y;}
    double sub(double x,double y)    //sub function
    {return x-y;}
    double mul(double x,double y)    //mul function
    {return x*y;}
    double div(double x,double y)    //div function
    {return x/y;}