利用指针变量调用他所指向的函数求定积分，列举了5个普通的函数，代码如下

本文链接：https://blog.youkuaiyun.com/progess_every_day/article/details/104860316

本文介绍了一个使用C语言实现的函数指针应用案例，通过一个简单的菜单选择不同的数学函数进行运算，包括二次函数积分、三次函数积分等。代码展示了如何定义函数指针并将其作为参数传递给另一个函数，实现灵活的函数调用。

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#include<stdio.h>
#include<math.h>
int main()
{
   float fun(float a, float b, float(*p)(float, float));
   float fun1(float,float);
   float fun2(float, float);
   float fun3(float, float);
   float fun4(float, float);
   float fun5(float, float);
   int n;
   printf("please input a number of function from 1 to 5:\n");
   scanf_s("%d", &n);
   switch (n)
   {
   case 1:printf("this is the first function,");
       fun(1, 4,fun1);
       break;
   case 2:printf("this is the second function,");
       fun(1, 4,fun2);
       break;
   case 3:printf("this is the third function,");
       fun(1, 4,fun3);
       break;
   case 4:printf("this is the 4th function,");
       fun(1, 4,fun4);
       break;
   case 5:printf("this is the 5th function,");
       fun(1, 4,fun5);
       break;
   default:printf("DATA ERROR");
   }
   return 0;
}
float fun(float x, float y, float(*p)(float, float))
{
   float result;
   result = (*p)(x, y);
   printf("the integrate of the function is %8.2f\n", result);
}
float fun1(float a, float b)
{
   float sum;
   sum = b + 0.5*b*b - a - 0.5*a*a;
   return sum;
}
float fun2(float a, float b)
{
   float sum;
   sum = b * b + 3 * b - a * a - 3 * a;
   return sum;
}
float fun3(float a, float b)
   {
       float sum;
       sum = exp(b) + b - exp(a) - a;
       return sum;
   }
float fun4(float a, float b)
{
   float sum;
   sum = (1.0 / 3.0)*(pow((1 + b), 3)) - (1.0 / 3.0)*(pow((1 + a), 3));
   return sum;
}
float fun5(float a, float b)
{
   float sum;
   sum = (1.0 / 4.0)*pow(b, 4) - (1.0 / 4.0)*pow(a, 4);
   return sum;
}