C: How to wrap a float to the interval [-pi, pi)

Question

I\'m looking for some nice C code that will accomplish effectively:

while (deltaPhase >= M_PI) deltaPhase -= M_TWOPI;
while (deltaPhase < -M_PI) deltaP         


        

Answer 1

Here is a version for other people finding this question that can use C++ with Boost:

#include 
#include 

template
inline T normalizeRadiansPiToMinusPi(T rad)
{
  // copy the sign of the value in radians to the value of pi
  T signedPI = boost::math::copysign(boost::math::constants::pi(),rad);
  // set the value of rad to the appropriate signed value between pi and -pi
  rad = fmod(rad+signedPI,(2*boost::math::constants::pi())) - signedPI;

  return rad;
} 

C++11 version, no Boost dependency:

#include 

// Bring the 'difference' between two angles into [-pi; pi].
template 
T normalizeRadiansPiToMinusPi(T rad) {
  // Copy the sign of the value in radians to the value of pi.
  T signed_pi = std::copysign(M_PI,rad);
  // Set the value of difference to the appropriate signed value between pi and -pi.
  rad = std::fmod(rad + signed_pi,(2 * M_PI)) - signed_pi;
  return rad;
}