Boost C++ Libraries: Ticket #6893: Inaccurate Radians/Degrees conversion

anonymous — Mon, 03 Nov 2014 16:04:34 GMT

Any update on this? I see the same constant is used in boost 1.54. It would be good to not introduce unnecessary and avoidable inaccuracies in such a foundational location.

owner, status changed

Jürgen Hunold — Wed, 05 Nov 2014 08:25:38 GMT

owner changed from Matthias Schabel to Jürgen Hunold
status new → assigned

anonymous — Fri, 16 Jan 2015 09:02:26 GMT

There already exist the necessary constants

boost::math::constants::radian (=180/pi)

and

boost::math::constants::degree (=pi/180)

Fri, 22 May 2015 20:32:30 GMT

The constants in boost/match/constants/constants.hpp certainly appear to have the necessary accuracy. I was somewhat surprised to see only 4 d.p. accuracy when using boost::units conversions between rad/grad/deg due to the low precision constants used here while I was writing unit tests to validate the conversions. Updating it to use the math constants would be much appreciated. Do you need a patch providing?

attachment set

rleigh@… — Wed, 10 Jun 2015 15:22:09 GMT

attachment → boost-angle-precision.patch

Use boost::math pi constant to increase precision

Wed, 10 Jun 2015 15:26:58 GMT

I have added a patch which makes the suggested change to use boost::math::constants::pi (actually, two_pi) to improve the precision. I've tested this locally and all my own unit tests continue to pass with the patched headers.

attachment set

Thu, 11 Jun 2015 07:06:43 GMT

attachment → boost-angle-precision2.patch

Updated patch; use degree constant directly (not possible for grad--no constant defined)

Mon, 22 Jun 2015 21:21:34 GMT

PR opened: https://github.com/boostorg/units/pull/18

anonymous — Sun, 08 Jul 2018 16:19:39 GMT

Please at least change the value to a more precise value if there is no agreement on the best way to retrieve the good value or if we don't want to introduce dependencies on other boost header.

Keeping a needlessly inaccurate value for 6 years is clearly the worst possible situation.