— Function: double gsl_sf_angle_restrict_symm (double theta)
— Function: int gsl_sf_angle_restrict_symm_e (double * theta)

These routines force the angle theta to lie in the range (-\pi,\pi].

— Function: double gsl_sf_angle_restrict_pos (double theta)
— Function: int gsl_sf_angle_restrict_pos_e (double * theta)

These routines force the angle theta to lie in the range [0, 2\pi).