chris jefferson wrote:
> I would like to say yes, I disagree that this should be true. By your
> argument, why isn't sin(pow(2.0,90.0)+1) == sin(6.153104..)? Also, how
> the heck do you intend to actually calculate that value? You can't just
> keep subtracting multiples of 2*pi from pow(2.0, 90.0) else nothing will
> happen, and if you choose to subtract some large multiple of 2*pi, your
> answer wouldn't end up accurate to anywhere near that many decimal
> places. Floating point numbers approximate real numbers, and at the size
> you are considering, the approximation contains values for which sin(x)
> takes all values in the range [-1,1].
Nonsense.
Show me an example where the following function should *not* print the
same values for a and b:
void same_sines(double x)
{
double a = sin(x);
double b = sin(fmod(x, 2.0 * PI));
printf("%20.15f,%20.15f\n",a,b);
}
Granted, -funsafe-math-optimizations *will* produce different values for
certain values, such as x = pow(2.0,90.0), on x87 hardware, but that is
an error in computing a, not a violation of principle.
..Scott
