Op di 12 jun. 2018 12:41 schreef Nathaniel Smith <n...@pobox.com>: > On Tue, Jun 12, 2018, 00:03 Stephan Houben <stephan...@gmail.com> wrote: > >> Hi all, >> >> I wrote a possible implementation of sindg: >> >> https://gist.github.com/stephanh42/336d54a53b31104b97e46156c7deacdd >> >> This code first reduces the angle to the [0,90] interval. >> After doing so, it can be observed that the simple implementation >> math.sin(math.radians(angle)) >> produces exact results for 0 and 90, and a result already rounded to >> nearest for >> 60. >> > > You observed this on your system, but math.sin uses the platform libm, > which might do different things on other people's systems. >
Ok, I updated the code to treat all the values 0, 30, 45, 60 and 90 specially. Stephan > >> For 30 and 45, this simple implementation is one ulp too low. >> So I special-case those to return the correct/correctly-rounded value >> instead. >> Note that this does not affect monotonicity around those values. >> > > Again, monotonicity is preserved on your system, but it might not be on > others. It's not clear that this matters, but then it's not clear that any > of this matters... > > -n >
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