<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">The paper is up at <a href="https://cs.brynmawr.edu/~rae/papers/2018/pat-tyvars/pat-tyvars.pdf" class="">https://cs.brynmawr.edu/~rae/papers/2018/pat-tyvars/pat-tyvars.pdf</a><div class=""><br class=""></div><div class="">But do see recent conversation on the ticket, as this may be undergoing more revision, allowing, say, existentials to work with this feature.</div><div class=""><br class=""></div><div class="">Richard<br class=""><div><br class=""><blockquote type="cite" class=""><div class="">On Jun 8, 2018, at 6:16 PM, Simon Peyton Jones via ghc-steering-committee <<a href="mailto:ghc-steering-committee@haskell.org" class="">ghc-steering-committee@haskell.org</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div class="WordSection1" style="page: WordSection1; font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;"><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span class="">See my reply on the Github thread.<o:p class=""></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span class="">Richard what do you think? Can you post the paper?<o:p class=""></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span class=""><o:p class=""> </o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span class="">Simon<o:p class=""></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span class=""><o:p class=""> </o:p></span></div><div style="border-style: none none none solid; border-left-width: 1.5pt; border-left-color: blue; padding: 0cm 0cm 0cm 4pt;" class=""><div class=""><div style="border-style: solid none none; border-top-width: 1pt; border-top-color: rgb(225, 225, 225); padding: 3pt 0cm 0cm;" class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><b class=""><span lang="EN-US" class="">From:</span></b><span lang="EN-US" class=""><span class="Apple-converted-space"> </span>ghc-steering-committee <<a href="mailto:ghc-steering-committee-bounces@haskell.org" class="">ghc-steering-committee-bounces@haskell.org</a>><span class="Apple-converted-space"> </span><b class="">On Behalf Of<span class="Apple-converted-space"> </span></b>Simon Marlow<br class=""><b class="">Sent:</b><span class="Apple-converted-space"> </span>08 June 2018 20:54<br class=""><b class="">To:</b><span class="Apple-converted-space"> </span>Manuel M T Chakravarty <<a href="mailto:chak@justtesting.org" class="">chak@justtesting.org</a>><br class=""><b class="">Cc:</b><span class="Apple-converted-space"> </span><a href="mailto:ghc-steering-committee@haskell.org" class="">ghc-steering-committee@haskell.org</a><br class=""><b class="">Subject:</b><span class="Apple-converted-space"> </span>Re: [ghc-steering-committee] Proposal: Or patterns #43 (Round 2)<o:p class=""></o:p></span></div></div></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">+1, but we should hear from Simon about the existential point.<o:p class=""></o:p></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">On 1 June 2018 at 08:30, Manuel M T Chakravarty <<a href="mailto:chak@justtesting.org" target="_blank" style="color: purple; text-decoration: underline;" class="">chak@justtesting.org</a>> wrote:<o:p class=""></o:p></div><blockquote style="border-style: none none none solid; border-left-width: 1pt; border-left-color: rgb(204, 204, 204); padding: 0cm 0cm 0cm 6pt; margin-left: 4.8pt; margin-right: 0cm;" class=""><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">We now have a revised version of the ”Or pattern” proposal #43 to consider:<o:p class=""></o:p></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""> (formatted) <a href="https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fosa1%2Fghc-proposals%2Fblob%2For_patterns%2Fproposals%2F0000-or-&data=02%7C01%7Csimonpj%40microsoft.com%7C97aa991a9856484a940e08d5cd798afa%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636640844264137789&sdata=Bkxgi6BdjD1xNptF28bekSybUBT9%2BdtkfIzMiOtpvQQ%3D&reserved=0" target="_blank" style="color: purple; text-decoration: underline;" class="">https://github.com/osa1/ghc-proposals/blob/or_patterns/proposals/0000-or-</a>patterns.rst<br class=""> (PR thread) <a href="https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fghc-proposals%2Fghc-proposals%2Fpull%2F43&data=02%7C01%7Csimonpj%40microsoft.com%7C97aa991a9856484a940e08d5cd798afa%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636640844264147806&sdata=lmj6p8TZ9hL096TRiYLMjWGGuLi0m8R0Vr9y5fF30Ug%3D&reserved=0" target="_blank" style="color: purple; text-decoration: underline;" class="">https://github.com/ghc-proposals/ghc-proposals/pull/43</a><o:p class=""></o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">You may remember that we discuss this a while back<o:p class=""></o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""> <a href="https://mail.haskell.org/pipermail/ghc-steering-committee/2017-November/000231.html" target="_blank" style="color: purple; text-decoration: underline;" class="">https://mail.haskell.org/pipermail/ghc-steering-committee/2017-November/000231.html</a><o:p class=""></o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">and finally decided to bounce it back to the authors with the following recommendation:<o:p class=""></o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""> <a href="https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fghc-proposals%2Fghc-proposals%2Fpull%2F43%23issuecomment-358189327&data=02%7C01%7Csimonpj%40microsoft.com%7C97aa991a9856484a940e08d5cd798afa%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636640844264157815&sdata=OfK54e4IqvNRarsHVjtd18xErq7IyY1svOCe2k9LdPQ%3D&reserved=0" target="_blank" style="color: purple; text-decoration: underline;" class="">https://github.com/ghc-proposals/ghc-proposals/pull/43#issuecomment-358189327</a><o:p class=""></o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">We previously decided that we are inclined to accept this proposal if the authors change the points that we highlighted. Judging from the conversation of SimonPJ and Richard with the author on the GitHub thread, it appears to me that most of the issues have been addressed. However, Simon’s point <o:p class=""></o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div></div><blockquote style="margin-left: 30pt; margin-right: 0cm;" class=""><div class=""><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">• "Patterns that bind existentials, dictionaries, or equalities are rejected by the type checker". I disagree. Earlier I suggested "no variable bound by an or-pattern can have a type that mentions an existential variable bound by the or-pattern". That is much more friendly because you can still match against an existential constructor; you just can’t bind an existential variable.<o:p class=""></o:p></div></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div></div></blockquote><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">from <<a href="https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fghc-proposals%2Fghc-proposals%2Fpull%2F43%23issuecomment-368933401&data=02%7C01%7Csimonpj%40microsoft.com%7C97aa991a9856484a940e08d5cd798afa%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636640844264157815&sdata=Mk975k%2B0RzaA5CnTu0vUcHbsJqU4QGaiouvHOOv1Z9s%3D&reserved=0" target="_blank" style="color: purple; text-decoration: underline;" class="">https://github.com/ghc-proposals/ghc-proposals/pull/43#issuecomment-368933401</a>> still doesn’t seem to be addressed, or am I misunderstanding?<o:p class=""></o:p></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">Overall, I propose to accept the proposal, possibly requiring that the above point be addressed.<o:p class=""></o:p></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">What do you all think?<o:p class=""></o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">Cheers,<o:p class=""></o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">Manuel<o:p class=""></o:p></div></div><div class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div></div></div></div><p class="MsoNormal" style="margin: 0cm 0cm 12pt; font-size: 11pt; font-family: Calibri, sans-serif;"><br class="">_______________________________________________<br class="">ghc-steering-committee mailing list<br class=""><a href="mailto:ghc-steering-committee@haskell.org" target="_blank" style="color: purple; text-decoration: underline;" class="">ghc-steering-committee@haskell.org</a><br class=""><a href="https://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-steering-committee" target="_blank" style="color: purple; text-decoration: underline;" class="">https://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-steering-committee</a><o:p class=""></o:p></p></blockquote></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div></div></div></div></div><span style="font-family: Helvetica; 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