double recursive_func(double x, double r, int iterate);

#ifdef _MSC_VER
double __stdcall F(double *x, double *r, int *iterate)
#else
double f_(double *x, double *r, int *iterate)
#endif
{
    return recursive_func(*x, *r, *iterate);
}

double recursive_func(double x, double r, int iterate)
{
    double f_, y;

    if(iterate > 1)
    {
        y = recursive_func(x, r, iterate - 1);
        f_ = 4*r*y*(1 - y);
    }
    else
        f_ = 4*r*x*(1 - x);
    return f_;
}