给你个参考代码，具体如下：

#include <stdio.h>
#define RES (1e-6)
double integ(double a,double b,double f(double))
{
    double sum;
    for(sum=0;a<b;a+=RES)
    {
        sum+=f(a)*RES;
    }
    return sum;
}
double f(double x)
{
    return x*x;
}
int main()
{
    printf("%lf\n",integ(0,0.1,f));
    return 0;
}