<div dir="ltr">Simon, Richard,<div><br></div><div>thank you for your answer! I don't have time to look into the GHC sources right now, but I will set aside some time after the holidays and take a close look at what the exact restrictions on proc-notation are and document them.</div><div><br></div><div>Since you suggested a rewrite of GHC's handling of proc-syntax, are there any opinions on integrating generalized arrows (Joseph 2014) in the process? I think they would greatly improve arrows! I don't know if I have the time to attempt this, but if I find the time I would give it a try. Why wasn't this integrated while it was still actively developed?</div><div><br></div><div>Best,</div><div>Jan</div><div><br></div><div>[Joseph 2014] <a href="https://www2.eecs.berkeley.edu/Pubs/TechRpts/2014/EECS-2014-130.pdf" target="_blank">https://www2.eecs.<wbr>berkeley.edu/Pubs/TechRpts/<wbr>2014/EECS-2014-130.pdf</a><br><div><br></div><div><br></div></div></div><div class="gmail_extra"><br><div class="gmail_quote">2016-11-29 12:41 GMT+00:00 Simon Peyton Jones <span dir="ltr"><<a href="mailto:simonpj@microsoft.com" target="_blank">simonpj@microsoft.com</a>></span>:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
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<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif">Jan,<u></u><u></u></span></p>
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<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif">Type checking and desugaring for arrow syntax has received Absolutely No Love for several years. I do not understand how it works very well, and I would not be at all surprised if it is broken
in corner cases.<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif">It really needs someone to look at it carefully, document it better, and perhaps refactor it – esp by using a different data type rather than piggy-backing on HsExpr.<u></u><u></u></span></p>
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<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif">In the light of that understanding, I think rebindable syntax will be easier.<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif">I don’t know if you are up for that, but it’s a rather un-tended part of GHC.<u></u><u></u></span></p>
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<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif">Thanks<u></u><u></u></span></p>
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<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif">Simon<u></u><u></u></span></p>
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<p class="MsoNormal"><b><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif">From:</span></b><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif"> ghc-devs [mailto:<a href="mailto:ghc-devs-bounces@haskell.org" target="_blank">ghc-devs-bounces@<wbr>haskell.org</a>]
<b>On Behalf Of </b>Richard Eisenberg<br>
<b>Sent:</b> 28 November 2016 22:30<br>
<b>To:</b> Jan Bracker <<a href="mailto:jan.bracker@googlemail.com" target="_blank">jan.bracker@googlemail.com</a>><br>
<b>Cc:</b> <a href="mailto:ghc-devs@haskell.org" target="_blank">ghc-devs@haskell.org</a><br>
<b>Subject:</b> Help needed: Restrictions of proc-notation with RebindableSyntax<u></u><u></u></span></p>
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<p class="MsoNormal">Jan’s question is a good one, but I don’t know enough about procs to be able to answer. I do know that the answer can be found by looking for uses of `tcSyntaxOp` in the TcArrows module.... but I just can’t translate it all to source Haskell,
having roughly 0 understanding of this end of the language.<u></u><u></u></p>
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<p class="MsoNormal">Can anyone else help Jan here?<u></u><u></u></p>
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<p class="MsoNormal">Richard<u></u><u></u></p>
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<p class="MsoNormal">On Nov 23, 2016, at 4:34 AM, Jan Bracker via ghc-devs <<a href="mailto:ghc-devs@haskell.org" target="_blank">ghc-devs@haskell.org</a>> wrote:<u></u><u></u></p>
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<p class="MsoNormal">Hello,<u></u><u></u></p>
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<p class="MsoNormal">I want to use the proc-notation together with RebindableSyntax. So far what I am trying to do is working fine, but I would like to know what the exact restrictions on the supplied functions are. I am introducing additional indices and constraints
on the operations. The documentation [1] says the details are in flux and that I should ask directly.<u></u><u></u></p>
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<p class="MsoNormal">Best,<u></u><u></u></p>
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<p class="MsoNormal">Jan<u></u><u></u></p>
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<p class="MsoNormal">[1] <a href="https://na01.safelinks.protection.outlook.com/?url=https:%2F%2Fdownloads.haskell.org%2F~ghc%2Flatest%2Fdocs%2Fhtml%2Fusers_guide%2Fglasgow_exts.html%23rebindable-syntax-and-the-implicit-prelude-import&data=02%7C01%7Csimonpj%40microsoft.com%7C80e472cedf78463bd18408d417de1af5%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636159690104764444&sdata=ygqePSmgcPKnPmKDBfZplkyjG9BIDBO1L1MWHNpqw88%3D&reserved=0" target="_blank">https://downloads.haskell.<wbr>org/~ghc/latest/docs/html/<wbr>users_guide/glasgow_exts.html#<wbr>rebindable-syntax-and-the-<wbr>implicit-prelude-import</a><u></u><u></u></p>
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