do_hard_work
do_hard_work(double x, double y, double *rx, int *B_is_usable, double *B,
do_hard_work(float x, float y, float *rx, int *B_is_usable, float *B,
do_hard_work(long double x, long double y, long double *rx, int *B_is_usable, long double *B, long double *sqrt_A2my2, long double *new_y)