<div dir="ltr"><div><div>Thanks.<br><br></div>And any thoughts on my proposal to do away with the braces/semi completely? I suspect GHC is the only significant body of code that uses that style still.<br><br></div>Alan<br><br></div><div class="gmail_extra"><br><div class="gmail_quote">On Thu, Nov 10, 2016 at 10:24 AM, Simon Peyton Jones <span dir="ltr"><<a href="mailto:simonpj@microsoft.com" target="_blank">simonpj@microsoft.com</a>></span> wrote:<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-size:11.0pt;font-family:"Calibri",sans-serif">I think it’s because the “;” is treated as part of the let not part of the do. After all, how does the implicit layout of the let know that the
let-bindings are finished?<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif">This should work<u></u><u></u></span></p><span class="">
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">foo<br>
= do { let { x = 1 };<br>
Just 5 }</span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"><u></u><u></u></span></p>
<p class="MsoNormal"><a name="m_-8633635087758701424__MailEndCompose"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"><u></u> <u></u></span></a></p>
</span><p class="MsoNormal"><span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif">Now the let bindings are clearly brought to an end. Or this<u></u><u></u></span></span></p><span class="">
<p class="MsoNormal"><span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"><u></u> <u></u></span></span></p>
<p class="MsoNormal"><span><span style="font-family:"Courier New"">foo<br>
= do { let x = 1<u></u><u></u></span></span></p>
<p class="MsoNormal"><span><span style="font-family:"Courier New""> ; Just 5 }<u></u><u></u></span></span></p>
<p class="MsoNormal"><span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"><u></u> <u></u></span></span></p>
</span><p class="MsoNormal"><span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif">Now the “’;” is to the left of the x=1 and so brings the let’s implicit layout to an end.
<u></u><u></u></span></span></p>
<p class="MsoNormal"><span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"><u></u> <u></u></span></span></p>
<p class="MsoNormal"><span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif">But not this!<u></u><u></u></span></span></p><span class="">
<p class="MsoNormal"><span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"><u></u> <u></u></span></span></p>
<p class="MsoNormal"><span><span style="font-family:"Courier New"">foo<br>
= do { let x = 1; Just 5 }<u></u><u></u></span></span></p>
<p class="MsoNormal"><span><span style="font-family:"Courier New""><u></u> <u></u></span></span></p>
</span><p class="MsoNormal"><span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif">So it’s a bug in the pretty-printer, not the parser<u></u><u></u></span></span></p>
<p class="MsoNormal"><span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"><u></u> <u></u></span></span></p>
<p class="MsoNormal"><span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif">SImon<u></u><u></u></span></span></p>
<p class="MsoNormal"><span><span style="font-family:"Courier New""><u></u> <u></u></span></span></p>
<p class="MsoNormal"><span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"><u></u> <u></u></span></span></p>
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<p class="MsoNormal"><b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif" lang="EN-US">From:</span></b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif" lang="EN-US"> 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>Alan & Kim Zimmerman<br>
<b>Sent:</b> 10 November 2016 07:01<br>
<b>To:</b> <a href="mailto:ghc-devs@haskell.org" target="_blank">ghc-devs@haskell.org</a><br>
<b>Subject:</b> ppr of HsDo<u></u><u></u></span></p>
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<p class="MsoNormal"><u></u> <u></u></p>
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<p class="MsoNormal" style="margin-right:0cm;margin-bottom:12.0pt;margin-left:0cm">
The pretty printer turns<br>
<br>
<span style="font-family:"Courier New"">foo = do<br>
let x = 1<br>
Just 5</span><u></u><u></u></p>
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<p class="MsoNormal" style="margin-right:0cm;margin-bottom:12.0pt;margin-left:0cm">
into<br>
<span style="font-family:"Courier New""><br>
foo<br>
= do { let x = 1;<br>
Just 5 }</span><u></u><u></u></p>
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<p class="MsoNormal" style="margin-right:0cm;margin-bottom:12.0pt;margin-left:0cm">
which does not parse, complaining about "parse error on input ‘Just’"<u></u><u></u></p>
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<p class="MsoNormal" style="margin-right:0cm;margin-bottom:12.0pt;margin-left:0cm">
Is this a parser error or a ppr problem? I am keen to fix the ppr to output <br>
<br>
<span style="font-family:"Courier New""><br>
foo<br>
= do let x = 1<br>
Just 5</span><u></u><u></u></p>
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<p class="MsoNormal" style="margin-right:0cm;margin-bottom:12.0pt;margin-left:0cm">
but I am not sure if there is a parser bug too.<u></u><u></u></p>
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<p class="MsoNormal" style="margin-right:0cm;margin-bottom:6.0pt;margin-left:0cm">
Alan<u></u><u></u></p>
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