[Haskell-cafe] A foray into type-level programming, and getting stuck
Wolfgang Jeltsch
g9ks157k at acme.softbase.org
Mon Mar 2 05:41:17 EST 2009
Am Sonntag, 1. März 2009 22:10 schrieb Brian Bloniarz:
> Hi George,
>
> Since none of the type metaprogramming specialists have answered you
> on-list, I took a crack at this -- I think you can work around the issue by
> avoiding overlapping instances entirely. I learned about this technique
> from the HList paper & this message:
> http://okmij.org/ftp/Haskell/keyword-arguments.lhs
> (see "the rest of the implementation").
Note that HList still needs overlapping instances for implementing type
equality. If we will have closed type families at some future time, this will
change. See:
<http://www.mail-archive.com/glasgow-haskell-users%40haskell.org/msg12792.html>
Best wishes,
Wolfgang
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