<br>2011/2/9 Simon Peyton-Jones:<br><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">Friends<br>
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Just a heads-up. Pedro is working on implementing "Generic Defaults", as described in his Haskell Symposium 2010 paper <a href="http://www.dreixel.net/research/pdf/gdmh_nocolor.pdf" target="_blank">www.dreixel.net/research/pdf/gdmh_nocolor.pdf</a><br>
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It will replace (and improve on) the "Derivable type classes" stuff in GHC at the moment, which was originally presented in a paper of that title that Ralf and I wrote in the 2000 Haskell workshop <a href="http://research.microsoft.com/en-us/um/people/simonpj/papers/derive.htm" target="_blank">http://research.microsoft.com/en-us/um/people/simonpj/papers/derive.htm</a>.<br>
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The "Derivable type class" extension is barely used, I believe, and isn't even documented in the manual. So I propose to switch from one to the other, rather than to try to support both. This change will happen in GHC 7.2 or 7.4, depending on when Pedro is done.<br>
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Please yell if you are a secret user of derivable type classes, so this change would discombobulate you.<br></blockquote><div><br>The only time I came across a use of it was in James Cheney's FreshLib [1]. I don't know if the latest version still uses it, though. There was also this bug [2] that prevented FreshLib from being compiled, but that is apparently fixed now.<br>
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[1] <a href="http://homepages.inf.ed.ac.uk/jcheney/programs/freshlib/">http://homepages.inf.ed.ac.uk/jcheney/programs/freshlib/</a><br></div></div>[2] <a href="http://hackage.haskell.org/trac/ghc/ticket/2824">http://hackage.haskell.org/trac/ghc/ticket/2824</a><br>
<br>Regards,<br>Sean<br>