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<p class="MsoNormal" style="mso-margin-top-alt:6.0pt;margin-right:0cm;margin-bottom:6.0pt;margin-left:36.0pt">
It seems to be a fairly popular proposal. =)<o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">Indeed. Ben Price (now at Strathclyde) did a short internship at MSR working on this; see<o:p></o:p></span></p>
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<a href="https://ghc.haskell.org/trac/ghc/wiki/TypeableT">https://ghc.haskell.org/trac/ghc/wiki/TypeableT</a><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">Dimitrios, Stephanie, Richard, and I are working on a paper about it, which should be out in a couple of weeks.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">At that point we’ll be in a position to have a proper core-libraries-committee discussion about the right API etc; I hope we can make
the result part of GHC 8.0. <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">But I want to get the paper out first since it gives a reasonably articulate exposition of the ideas and rationale, so that we all
start on the same page.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">Simon<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US"><o:p> </o:p></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"> Libraries [mailto:libraries-bounces@haskell.org]
<b>On Behalf Of </b>Edward Kmett<br>
<b>Sent:</b> 29 September 2015 16:53<br>
<b>To:</b> Roman Cheplyaka<br>
<b>Cc:</b> Haskell Libraries<br>
<b>Subject:</b> Re: Can we simplify Dynamic?<o:p></o:p></span></p>
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<p class="MsoNormal" style="mso-margin-top-alt:6.0pt;margin-right:0cm;margin-bottom:6.0pt;margin-left:0cm">
It seems to be a fairly popular proposal. =)<o:p></o:p></p>
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<o:p> </o:p></p>
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<a href="https://na01.safelinks.protection.outlook.com/?url=https%3a%2f%2fmail.haskell.org%2fpipermail%2flibraries%2f2014-August%2f023633.html&data=01%7c01%7csimonpj%40064d.mgd.microsoft.com%7c4a20632c14424882676b08d2c8e5fe0e%7c72f988bf86f141af91ab2d7cd011db47%7c1&sdata=Q8v9rdZ4Q%2bnw7oER7kBQb42HIXiujZOEmkO%2fQPOqe0g%3d">https://mail.haskell.org/pipermail/libraries/2014-August/023633.html</a><o:p></o:p></p>
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<o:p> </o:p></p>
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-Edward<o:p></o:p></p>
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<o:p> </o:p></p>
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On Mon, Sep 28, 2015 at 6:03 PM, Roman Cheplyaka <<a href="mailto:roma@ro-che.info" target="_blank">roma@ro-che.info</a>> wrote:<o:p></o:p></p>
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I suggested this last year, see this thread<br>
<a href="https://na01.safelinks.protection.outlook.com/?url=https%3a%2f%2fmail.haskell.org%2fpipermail%2flibraries%2f2014-March%2f022287.html&data=01%7c01%7csimonpj%40064d.mgd.microsoft.com%7c4a20632c14424882676b08d2c8e5fe0e%7c72f988bf86f141af91ab2d7cd011db47%7c1&sdata=NllZIb67%2fxgH1fNXfMJ5nsgWm%2bwRpfXEBWt4kPlS9AM%3d" target="_blank">https://mail.haskell.org/pipermail/libraries/2014-March/022287.html</a><o:p></o:p></p>
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<br>
On 09/29/2015 12:51 AM, David Feuer wrote:<br>
> Currently,<br>
><br>
> data Dynamic = Dynamic TypeRep Obj<br>
> deriving Typeable<br>
> where<br>
> type Obj = Any<br>
><br>
> As a result, all of the operations must be implemented "by hand" using<br>
> unsafeCoerce. The more obvious representation these days would seem to be<br>
><br>
> data Dynamic where<br>
> Dynamic :: Typeable a => a -> Dynamic<br>
><br>
> Most of the operations then become trivial applications of Typeable<br>
> functions. The only exceptions seem to be dynApply and dynApp. That<br>
> there are exceptions strikes me as quite unfortunate. The easiest fix is<br>
> inspired by the fact that Data.Dynamic uses<br>
><br>
> funResultTy :: TypeRep -> TypeRep -> Maybe TypeRep<br>
><br>
> from Data.Typeable to decide whether to coerce. It seems reasonable to<br>
> add a more informative version, something like<br>
><br>
> applyTypeable :: (Typeable f, Typeable a) =><br>
> proxy f -><br>
> proxy a -><br>
> (forall b . (Typeable b, f ~ (a -> b)) => r) -><br>
> Maybe r<br>
><br>
> On the other hand, it would be really cool if there were some more<br>
> general way to get type-level information out of Typeable instances,<br>
> pattern matching on the type constructors.<br>
<br>
<o:p></o:p></p>
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<br>
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