Заменить цикл рекурсией - C (СИ)

float result(double x1, double e)
{
    double x2;
    float temp;
    x2 = x1;
    Ufunction = function;
    Ufunction1 = function1;
    do
    {
        c = x2;
        x2 = c - (*function)(c) / (*function1)(c);
        temp = (float)abs(x2 - c);
    } while (temp> e);
    res = x2;
    return res;
}