<html><body><div dir=""><div dir="ltr">
Dear all,</div><div dir="ltr"><br></div><div dir="ltr">To be honest, I’m still trying to make up my mind about this. If we were to accept the proposal, I think option (1) is the best one, since it otherwise `\case` would have a different behaviour depending on whether you have -XLambdaCase or -XExtendedLambdaCase on.</div><div dir="ltr"><br></div><div dir="ltr">Having said so, the words of Simon M. and Richard resonate with me: do we really want \case, \cases, if|, all in the language?</div><div dir="ltr">- I would prefer one single way to do stuff, let’s say having a `cases … of` which also works as case, if|… and then a \cases for lambdas;</div><div dir="ltr">- but this is not the world we live in! We already have those things, and this would be yet another small syntactic addition, so we need to think about whether the language is becoming too big.</div><div dir="ltr"><br></div><div dir="ltr">So right now I’m in favor of option (X), reject the proposal.</div><div dir="ltr"><br></div><div dir="ltr">Regards,</div><div dir="ltr">Alejandro</div><div dir="ltr"><br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">El 24 jun 2021 12:52:10, Simon Peyton Jones via ghc-steering-committee <<a href="mailto:ghc-steering-committee@haskell.org">ghc-steering-committee@haskell.org</a>> escribió:<br></div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div>
<div>
<meta http-equiv="Content-Type" content="text/html; charset=us-ascii">
<meta name="Generator" content="Microsoft Word 15 (filtered medium)">
</div>
<div lang="EN-GB" link="#0563C1" vlink="#954F72" style="word-wrap:break-word">
<div class="WordSection1">
<p class="MsoNormal">Dear Steering committee</p>
<p class="MsoNormal">Simon and Joachim have responded, but only those two . Please reply!</p>
<p class="MsoNormal">Thanks</p>
<p class="MsoNormal">Simon</p>
<p class="MsoNormal"> </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" style="margin:0cm"><b><span lang="EN-US" style="mso-fareast-language:EN-GB">From:</span></b><span lang="EN-US" style="mso-fareast-language:EN-GB"> ghc-steering-committee <<a href="mailto:ghc-steering-committee-bounces@haskell.org">ghc-steering-committee-bounces@haskell.org</a>>
<b>On Behalf Of </b>Simon Peyton Jones via ghc-steering-committee<br>
<b>Sent:</b> 15 June 2021 13:52<br>
<b>To:</b> Joachim Breitner <<a href="mailto:mail@joachim-breitner.de">mail@joachim-breitner.de</a>>; <a href="mailto:ghc-steering-committee@haskell.org">ghc-steering-committee@haskell.org</a><br>
<b>Subject:</b> Re: [ghc-steering-committee] Proposal #302: `\of` (New Shepherd: Simon PJ)</span></p>
</div>
</div>
<p class="MsoNormal"> </p>
<p class="MsoPlainText">| I’d like to reassing shepherding of this one.</p>
<p class="MsoPlainText">| </p>
<p class="MsoPlainText">| It seems to be clear that we want “something like this”, there are many ways</p>
<p class="MsoPlainText">| to skin the cat, so it comes down to opinion and what we need is a decision</p>
<p class="MsoPlainText">| (or a call to votes). As with anything that’s possibly quite opinionated,</p>
<p class="MsoPlainText">| it’s good to have an authorative voice, so in this case, Simon PJ.</p>
<p class="MsoPlainText">| </p>
<p class="MsoPlainText">| Simon, can you either come up with a “all things considered, I think this</p>
<p class="MsoPlainText">| variant is the (narrowly) the best” recommendation or, alternative, a</p>
<p class="MsoPlainText">| “please vote on the following options” verdict?</p>
<p class="MsoPlainText"> </p>
<p class="MsoPlainText"><span style="font-family:"Calibri",sans-serif">OK, to remind everyone</span></p>
<ul style="margin-top:0cm" type="disc">
<li class="MsoPlainText" style="mso-list:l3 level1 lfo3"><span style="font-family:"Calibri",sans-serif">Here is the proposal:
<a href="https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2FJakobBruenker%2Fghc-proposals%2Fblob%2Fpatch-1%2Fproposals%2F0000-lambda-layout.md&data=04%7C01%7Csimonpj%40microsoft.com%7C0903e8fd7cbe4aadc88b08d92ffc71d2%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637593584027236069%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C2000&sdata=DNZOpilyGrWdTDQyaqEgf1orDNQNX9ZwbMwmGYAk64g%3D&reserved=0">
https://github.com/JakobBruenker/ghc-proposals/blob/patch-1/proposals/0000-lambda-layout.md</a></span></li><li class="MsoPlainText" style="mso-list:l3 level1 lfo3"><span style="font-family:"Calibri",sans-serif">Here is the discussion:
<a href="https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fghc-proposals%2Fghc-proposals%2Fpull%2F302&data=04%7C01%7Csimonpj%40microsoft.com%7C0903e8fd7cbe4aadc88b08d92ffc71d2%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637593584027246062%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C2000&sdata=LXuEVBuMxQlbF0elOS2792K5avMW3SeIYEuEDyyFmmo%3D&reserved=0">
https://github.com/ghc-proposals/ghc-proposals/pull/302</a></span></li></ul>
<p class="MsoPlainText"><span style="font-family:"Calibri",sans-serif"> </span></p>
<p class="MsoPlainText"><span style="font-family:"Calibri",sans-serif">The basic idea is to extend to lambda all the facilities that you get with function definitions, especially multiple patterns and guards. This seems clearly a good idea, whose only obstacle
is syntactic. There are no conceptual or specification challenges. The only point at issue is that of concrete syntax.</span></p>
<p class="MsoPlainText"><span style="font-family:"Calibri",sans-serif"> </span></p>
<p class="MsoPlainText"><span style="font-family:"Calibri",sans-serif">The proposal offers four possible syntactic options. After reviewing, I propose to discard (2) and (3) leaving these alternatives</span></p>
<p class="MsoPlainText"><span style="font-family:"Calibri",sans-serif"> </span></p>
<ul style="margin-top:0cm" type="disc">
<li class="MsoListParagraph" style="margin-left:0cm"><b>Option (1)
</b>\cases { p1 p2 -> rhs1; q1 q2 -> rhs2 }</li></ul>
<ul style="margin-top:0cm" type="disc">
<ul style="margin-top:0cm" type="circle">
<li class="MsoListParagraph" style="margin-left:0cm">Lives alongside \case, but allows multiple patterns</li><li class="MsoListParagraph" style="margin-left:0cm">Other keywords are possible, but I think it must be a variant on \case</li></ul>
</ul>
<ul style="margin-top:0cm" type="disc">
<li class="MsoListParagraph" style="margin-left:0cm"><b>Option (4)</b> Same, but use \case as the keyword</li></ul>
<ul style="margin-top:0cm" type="disc">
<ul style="margin-top:0cm" type="circle">
<li class="MsoListParagraph" style="margin-left:0cm">Incompatible with existing \case => extended transition period, unhappy users</li><li class="MsoListParagraph" style="margin-left:0cm">\case { (Just x) -> rhs1; Nothing -> rhs2 } will require parens forever, which in the common case of a one argument lambda see clunky.</li></ul>
</ul>
<ul style="margin-top:0cm" type="disc">
<li class="MsoListParagraph" style="margin-left:0cm"><b>Option (X).</b> Reject the proposal.</li></ul>
<p class="MsoNormal"> </p>
<p class="MsoNormal">Personally I favour (1). I’m relaxed about having multiple ways of saying the thing (think of let vs where), and I see no harm provided the two constructs look and behave the same. I’ve decided I like \cases precisely because it’s the
plural of \case, which is exactly what is going on.</p>
<p class="MsoNormal">I think we’ll end up having to vote on this, which is fine when it’s a judgement call about syntax. But first:</p>
<ul style="margin-top:0cm" type="circle">
<li class="MsoListParagraph" style="margin-left:0cm"><b>Are there any other alternatives you
<i>strongly</i> want on the ballot?</b></li></ul>
<p class="MsoNormal">I say “strongly” because I don’t want to open up a big new debate… we at the stage of trying to narrow options.</p>
<p class="MsoNormal">Thanks</p>
<p class="MsoNormal">Simon</p>
</div>
</div>
</div>
</div>
<div>
<div>
_______________________________________________<br>ghc-steering-committee mailing list<br><a href="mailto:ghc-steering-committee@haskell.org">ghc-steering-committee@haskell.org</a><br><a href="https://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-steering-committee">https://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-steering-committee</a><br>
</div>
</div>
</blockquote>
</div>
</div></div></body></html>