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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Verdana","sans-serif";color:#1F497D">For the record, I’m good with going ahead with “Solution 2” on
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<p class="MsoNormal" style="text-indent:5.25pt"><span style="font-size:11.0pt;font-family:"Verdana","sans-serif";color:#1F497D"><a href="http://hackage.haskell.org/trac/ghc/wiki/GhcKinds/KindsWithoutData">http://hackage.haskell.org/trac/ghc/wiki/GhcKinds/KindsWithoutData</a><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Verdana","sans-serif";color:#1F497D">if anyone wants to execute on it.<o:p></o:p></span></p>
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Simon<o:p></o:p></span></p>
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<p class="MsoNormal"><b><span lang="EN-US" style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span lang="EN-US" style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> ghc-devs-bounces@haskell.org [mailto:ghc-devs-bounces@haskell.org]
<b>On Behalf Of </b>Iavor Diatchki<br>
<b>Sent:</b> 02 April 2013 17:49<br>
<b>To:</b> Richard Eisenberg<br>
<b>Cc:</b> José Pedro Magalhães; ghc-devs<br>
<b>Subject:</b> Re: What promotes to (* :: BOX) ?<o:p></o:p></span></p>
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<p class="MsoNormal">Hello,<o:p></o:p></p>
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<p class="MsoNormal">I've been using an existential quantifier for this. It<o:p></o:p></p>
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<p class="MsoNormal">looks weird (and I think we should fix this as discussed) but it is the current workaround:<o:p></o:p></p>
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<p class="MsoNormal"><span style="font-family:"Courier New"">data MyKind = forall star. T star</span><o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><span style="font-family:"Courier New"">-- T :: * -> MyKind</span><o:p></o:p></p>
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<p class="MsoNormal">-Iavor<o:p></o:p></p>
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<p class="MsoNormal">On Tue, Apr 2, 2013 at 7:11 AM, Richard Eisenberg <<a href="mailto:eir@cis.upenn.edu" target="_blank">eir@cis.upenn.edu</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal">For more immediate satisfaction (i.e., before we get around to updating GHC in the manner suggested on the wiki page), you have to use a parameterized type and then specialize it to *:<o:p></o:p></p>
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<p class="MsoNormal">> data Prom2 a = Typic a<o:p></o:p></p>
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<p class="MsoNormal">Now, we have (Prom2 * :: BOX) with (Typic Int :: Prom2 *).<o:p></o:p></p>
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<p class="MsoNormal">Unfortunately, we have no kind synonyms, so you have to insert the * parameter every time you want to use the Prom2 kind. As Pedro suggests, this is a known weakness of the current system.<o:p></o:p></p>
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<p class="MsoNormal"><span style="color:#888888">Richard<o:p></o:p></span></p>
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<p class="MsoNormal">On Apr 2, 2013, at 8:55 AM, José Pedro Magalhães <<a href="mailto:jpm@cs.uu.nl" target="_blank">jpm@cs.uu.nl</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt">Hi Gabor,<br>
<br>
See <a href="http://hackage.haskell.org/trac/ghc/wiki/GhcKinds/KindsWithoutData" target="_blank">
http://hackage.haskell.org/trac/ghc/wiki/GhcKinds/KindsWithoutData</a><br>
Comments on that discussion are welcome.<br>
<br>
<br>
Cheers,<br>
Pedro<o:p></o:p></p>
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<p class="MsoNormal">On Tue, Apr 2, 2013 at 2:51 PM, Gabor Greif <<a href="mailto:ggreif@gmail.com" target="_blank">ggreif@gmail.com</a>> wrote:<o:p></o:p></p>
<p class="MsoNormal">Hi devs!<br>
<br>
I guess I found a gap in the promotion mechanism:<br>
<br>
> data Prom1 = Symic Symbol<br>
<br>
gets promoted to to a kind (Prom1 :: BOX) with (Symic "AAA" :: Prom1).<br>
So far so good.<br>
<br>
But how can I define by promotion (Prom2 :: BOX) with (Typic Int :: Prom2) ?<br>
<br>
I'd like to write<br>
<br>
> data Prom2 = Typic Type<br>
<br>
but haven't found such a beast in TypeLits. So my question is<br>
basically, which type-level identifier promotes to (* :: BOX) when<br>
mentioned in a `data` definition?<br>
<br>
I am thankful for any hints!<br>
<br>
Cheers,<br>
<br>
Gabor<br>
<br>
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