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

I encountered this question when searching for how to wrap a floating point value (or a double) between two arbitrary numbers. It didn't answer specifically for my case, so I worked out my own solution which can be seen here. This will take a given value and wrap it between lowerBound and upperBound where upperBound perfectly meets lowerBound such that they are equivalent (ie: 360 degrees == 0 degrees so 360 would wrap to 0)

Hopefully this answer is helpful to others stumbling across this question looking for a more generic bounding solution.

double boundBetween(double val, double lowerBound, double upperBound){
   if(lowerBound > upperBound){std::swap(lowerBound, upperBound);}
   val-=lowerBound; //adjust to 0
   double rangeSize = upperBound - lowerBound;
   if(rangeSize == 0){return upperBound;} //avoid dividing by 0
   return val - (rangeSize * std::floor(val/rangeSize)) + lowerBound;
}

A related question for integers is available here: Clean, efficient algorithm for wrapping integers in C++