[Boost-bugs] [Boost C++ Libraries] #12581: cpp_bin_float: Anal fixation. Part 4. Special cases of atan2()

Subject: [Boost-bugs] [Boost C++ Libraries] #12581: cpp_bin_float: Anal fixation. Part 4. Special cases of atan2()
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2016-11-04 01:51:19

#12581: cpp_bin_float: Anal fixation. Part 4. Special cases of atan2()
------------------------------+----------------------------
 Reporter:  Michael Shatz     |      Owner:  johnmaddock
     Type:  Feature Requests  |     Status:  new
Milestone:  To Be Determined  |  Component:  multiprecision
  Version:  Boost 1.62.0      |   Severity:  Cosmetic
 Keywords:  atan2             |
------------------------------+----------------------------
 In following special cases boost::atan2(y, x) return values are different
 from C RTL:

 {{{
   y     x  C RTL  boost
  inf  inf  pi/4   nan
 -inf  inf -pi/4   nan
  inf -inf  3*pi/4 nan
 -inf -inf -3*pi/4 nan
 -0   -val -pi     pi
  0    nan  nan    0
  inf  nan  nan    pi/2
 -inf  nan  nan   -pi/2
 }}}

 The first four boost answer make sense. IMHO, they are better than C RTL
 answers.
 The fifth boost answer is strange, but can be considered acceptable.
 The rest are plain bugs - nan should always propagate.

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/12581>
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