#### 7.31.5 Restriction Functions

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.