<html xmlns:v="urn:schemas-microsoft-com:vml" 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=us-ascii">
<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;
margin-bottom:.0001pt;
font-size:11.0pt;
font-family:"Calibri",sans-serif;}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:blue;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{mso-style-priority:99;
color:purple;
text-decoration:underline;}
p.Code, li.Code, div.Code
{mso-style-name:Code;
margin-top:0cm;
margin-right:0cm;
margin-bottom:0cm;
margin-left:36.0pt;
margin-bottom:.0001pt;
font-size:9.0pt;
font-family:"Courier New";}
p.msonormal0, li.msonormal0, div.msonormal0
{mso-style-name:msonormal;
margin:0cm;
margin-bottom:.0001pt;
font-size:11.0pt;
font-family:"Calibri",sans-serif;}
span.EmailStyle20
{mso-style-type:personal-reply;
font-family:"Calibri",sans-serif;
color:windowtext;
font-weight:normal;
font-style:normal;
text-decoration:none none;}
.MsoChpDefault
{mso-style-type:export-only;
font-size:10.0pt;}
@page WordSection1
{size:612.0pt 792.0pt;
margin:72.0pt 72.0pt 72.0pt 72.0pt;}
div.WordSection1
{page:WordSection1;}
--></style><!--[if gte mso 9]><xml>
<o:shapedefaults v:ext="edit" spidmax="1026" />
</xml><![endif]--><!--[if gte mso 9]><xml>
<o:shapelayout v:ext="edit">
<o:idmap v:ext="edit" data="1" />
</o:shapelayout></xml><![endif]-->
</head>
<body lang="EN-GB" link="blue" vlink="purple">
<div class="WordSection1">
<p class="MsoNormal" style="margin-left:36.0pt"><span style="font-size:12.0pt;color:black">Are you as convinced as you were of the semantics of pattern synonyms? I can see they are the right semantics given a run-time implementation but the alternative compile-time
implementation has a lot to recommend it.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt">What exactly is “the alternative compile-time implementation”?<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt">Remember, although pattern synonyms are set up to call a matching function,
<b>that matching function is often inlined</b>, which reduces the overhead to zero.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt">I say “often” inlined. An INLINE pragma for pattern synonyms would be a good feature.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt">Widening to ghc-devs.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt">Simon<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt"><o:p> </o:p></span></p>
<div style="border:none;border-left:solid blue 1.5pt;padding:0cm 0cm 0cm 4.0pt">
<div>
<div style="border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0cm 0cm 0cm">
<p class="MsoNormal"><b><span lang="EN-US">From:</span></b><span lang="EN-US"> Matthew Roberts <matthew.roberts@mq.edu.au>
<br>
<b>Sent:</b> 11 February 2019 00:10<br>
<b>To:</b> matthew.pickering@cs.ox.ac.uk; gergo@erdi.hu; Simon Peyton Jones <simonpj@microsoft.com>; rae@cs.brynmawr.edu<br>
<b>Subject:</b> Performance of pattern synonyms<o:p></o:p></span></p>
</div>
</div>
<p class="MsoNormal"><o:p> </o:p></p>
<div>
<p class="MsoNormal"><span style="font-size:12.0pt;color:black">Hi all,<o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span style="font-size:12.0pt;color:black"><o:p> </o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span style="font-size:12.0pt;color:black">I am working with someone on a compile-time pattern matching extension and the most important prior work is pattern synonyms in Haskell. I hope you might indulge a couple of questions I have not
been able to answer myself from the literature:<o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span style="font-size:12.0pt;color:black"><o:p> </o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span style="font-size:12.0pt;color:black"> * [In my testing](<a href="https://nam06.safelinks.protection.outlook.com/?url=http%3A%2F%2Fpattern-benchmarks.herokuapp.com%2Fposts%2F2019-02-09-peano.html&data=02%7C01%7Csimonpj%40microsoft.com%7Cf4d58b9dd66c476d591a08d68fb549cd%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636854406149018023&sdata=uehvVhVMCpNiYWp7Lr2pRLGqVSqt3gQTACl2kvS9crg%3D&reserved=0">http://pattern-benchmarks.herokuapp.com/posts/2019-02-09-peano.html</a>),
pattern synonyms have remarkable performance, has anyone ever benchmarked them before?<o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span style="font-size:12.0pt;color:black"> * Do you have - on hand - the hackage data you used in investigating uses of pattern synonyms? I am looking for real-world usage of pattern matching extensions.<o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span style="font-size:12.0pt;color:black"> * Are you as convinced as you were of the semantics of pattern synonyms? I can see they are the right semantics given a run-time implementation but the alternative compile-time implementation
has a lot to recommend it.<o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span style="font-size:12.0pt;color:black"><o:p> </o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span style="font-size:12.0pt;color:black">Thanks for your time,<o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span style="font-size:12.0pt;color:black"><o:p> </o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span style="font-size:12.0pt;color:black">Matt Roberts<o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span style="font-size:12.0pt;color:black">Department of Computing, Macquarie University<o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span style="font-size:12.0pt;color:black"><o:p> </o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span style="font-size:12.0pt;color:black"><o:p> </o:p></span></p>
</div>
</div>
</div>
</body>
</html>