Question

Given the function:

void Arc::SetAngles(double startAngle, double endAngle) {
    while(endAngle > (startAngle + 359.0)) endAngle -= 1.0;
    while(startAngle > 360.0) startAngle -= 360.0;
    while(startAngle < -360.0) startAngle += 360.0;
    while(endAngle > 360.0) endAngle -= 360.0;
    while(endAngle < -360.0) endAngle += 360.0;
    _startAngle = DegreeToRadian(startAngle);
    _endAngle = DegreeToRadian(endAngle);
}

Is there an algebraic solution to those while loops? It just looks…ugly. (Not to mention…slow.)

Answer 1

In C or C++ you’d use fmod to get rid of some of your loops. Instead of this:

while(startAngle > 360.0) startAngle -= 360.0;
while(startAngle < -360.0) startAngle += 360.0;

Do this:

startAngle = fmod(startAngle, 360.0);
if(startAngle < 0)
    startAngle += 360.0;

Don’t use the normal modulus operator (%) as that’s for integers and won’t do the right thing with floating point values.

Your first loop:

while(endAngle > (startAngle + 359.0)) endAngle -= 1.0;

Can be replaced with just this:

if(endAngle > startAngle + 359.0)
    endAngle = startAngle + 359.0;

But I think you should rethink that part of your algorithm: there’s no point in comparing the angles before you normalize them to the [0,360) interval.