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<p class="MsoNormal"><span style="font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US">(a ~ b) is a
<b>boxed</b>, <b>nominal</b> equality.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US">(a ~R# b) is an
<b>unboxed, representational</b> equality<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US">So it is rightly rejected.
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US"><br>
For the boxed/unboxed thing, the paper “practical aspects…” gives more detail. <a href="http://research.microsoft.com/en-us/um/people/simonpj/papers/ext-f/">
http://research.microsoft.com/en-us/um/people/simonpj/papers/ext-f/</a><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US">I think you already know about the nominal/representational distinction.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="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-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""> Glasgow-haskell-users [mailto:glasgow-haskell-users-bounces@haskell.org]
<b>On Behalf Of </b>Conal Elliott<br>
<b>Sent:</b> 24 April 2014 01:29<br>
<b>To:</b> glasgow-haskell-users@haskell.org; ghc-devs@haskell.org; Richard Eisenberg; Simon Peyton Jones<br>
<b>Subject:</b> Help with cast error<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></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">
I'd appreciate help with a cast-related Core Lint error I'm getting with a GHC plugin I'm working on:<br>
<br>
<span style="font-family:"Courier New""> Argument value doesn't match argument type:<br>
Fun type:<br>
Enc (Vec ('S 'Z) Bool) ~ (Bool, ()) =><br>
EP (Enc (Vec ('S 'Z) Bool)) -> EP (Bool, ())<br>
Arg type:<br>
~R# (Enc (Vec ('S 'Z) Bool)) (Bool, ())<br>
Arg:<br>
CO Sub (TFCo:R:EncVec[0] <'Z>_N <Bool>_N)<br>
; (Sub TFCo:R:EncBool[0], Sub (TFCo:R:EncVec0[0] <Bool>_N))_R</span><br>
<br>
(I omitted the module prefixes for brevity.) Do I have a role wrong here, or maybe something more fundamental?<br>
<br>
I can easily supply more info if it'd help.<br>
<br>
Thanks, -- Conal<o:p></o:p></p>
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