— 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].

Note that the mathematical value of \pi is slightly greater than M_PI, so the machine numbers M_PI and -M_PI are included in the range.

— 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).

Note that the mathematical value of 2\pi is slightly greater than 2*M_PI, so the machine number 2*M_PI is included in the range.