<html xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=Windows-1252">
<meta name="Generator" content="Microsoft Word 15 (filtered medium)">
<style><!--
/* Font Definitions */
@font-face
{font-family:"Cambria Math";
panose-1:2 4 5 3 5 4 6 3 2 4;}
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0cm;
font-size:11.0pt;
font-family:"Calibri",sans-serif;}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:blue;
text-decoration:underline;}
.MsoChpDefault
{mso-style-type:export-only;}
@page WordSection1
{size:612.0pt 792.0pt;
margin:72.0pt 72.0pt 72.0pt 72.0pt;}
div.WordSection1
{page:WordSection1;}
--></style>
</head>
<body lang="EN-GB" link="blue" vlink="#954F72" style="word-wrap:break-word">
<div class="WordSection1">
<p class="MsoNormal">Hi all – I now have fixes for all the issues I’m aware of. However, it’s quite possible I’ve made a mistake somewhere (either in the new code or the testing), so if anyone would like to help review either please let me know.</p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><b>Group 1 issues</b> (real numbers in Windows, where the defects are in mingw-w64: I’ve raised issue
<a href="https://gitlab.haskell.org/ghc/ghc/-/issues/20424">#20424</a> for this. The fixes (commits
<a href="https://github.com/mingw-w64/mingw-w64/commit/66ba5f3221c786de24f5fc4b9c0236b704c2d31d">
66ba5f32</a> and <a href="https://github.com/mingw-w64/mingw-w64/commit/021dffb8a482eb9d1b39569cd1ea42b87226fdf7">
021dffb8a</a>) have been made in mingw-w64 and are getting integrated into Haskell soon.</p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><b>Group 2 issues</b> (complex numbers, where the defects are in Complex.hs). I’ve raised issue
<a href="https://gitlab.haskell.org/ghc/ghc/-/issues/20425">#20425</a> for this and have the code fixes
<a href="https://gitlab.haskell.org/davjam/ghc/-/blob/ComplexBranchCuts/libraries/base/Data/Complex.hs">
here</a>. The new code changes many of the functions (I’ve given examples in the issue) and adds a few. I’ve also put the Haddock output
<a href="https://davjam.github.io/HaskellNumericsTestsFixes/TrigDiags/Data-Complex.html">
here</a>. (It now defines and gives an explanation of the branch cuts). I’ve also put some diagrams
<a href="https://davjam.github.io/HaskellNumericsTestsFixes/TrigDiags/Curr.html">
here</a> illustrating some of the problems.</p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I’ve done about as much testing as I can think of, using the code
<a href="https://github.com/davjam/HaskellNumericsTestsFixes/blob/main/ComplexTests.hs">
here</a>. Ideally I’d bulk-test against a reliable independent source, but can’t find one. AFAICT
<a href="https://www.wolframalpha.com/input/?i=sin%28-0.0%29">WolframAlpha</a>, Excel, gnumeric, CLISP don’t support negative zeros.
<a href="https://www.python.org/">Python</a> seems to, but cmath has incorrect branch cuts (cmath.sqrt(-4-0j) gives 2j).
<a href="https://www.advanpix.com/2016/04/28/branch-cuts-and-signed-zeros-in-matlab/">
Matlab</a> also seems deficient in a number of areas. (Hmmm: maybe no one cares about these working correctly??)<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Sorry about the delay in sending this, David.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
</body>
</html>