函数指针

double f(double x)
{
    return 2 * x;
}

double sum(double (*f)(double d), int n, int m)
{
    double result = 0;

    for (int i = n; i <=m; i++)
    {
        result += f(i);
    }

    return result;
}

int main()
{
    sum(f, 1, 10);
}