#3699: Wildcards in type functions
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Reporter: MartijnVanSteenbergen | Owner:
Type: feature request | Status: new
Priority: normal | Milestone: 6.14 branch
Component: Compiler | Version: 6.10.4
Resolution: | Keywords:
Difficulty: | Os: Unknown/Multiple
Testcase: | Architecture: Unknown/Multiple
Failure: None/Unknown |
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Comment (by MartijnVanSteenbergen):
Continuing this line of thought, instances for this family go hand in hand
with instances for this type class:
{{{
class MkErrorAlgebra f where
mkErrorAlgebra :: ErrorAlg f e a -> ErrorAlgPF f e a
}}}
Would it then also make sense to write:
{{{
instance MkErrorAlgebra f => MkErrorAlgebra (f :>: _) where
mkErrorAlgebra alg (Tag f) = mkErrorAlgebra alg f
}}}
?
Just a wild idea which I'm not sure yet I like or dislike. It does fit in
with the idea of not making up names if you don't have to. For that reason
I also prefer writing {{{data D :: <kind> where}}} for GADTs rather than
making up arbitrary names for the type arguments. Going even further, this
idea can be extended to e.g. {{{data Const a _ = Const a}}} for normal
ADTs.
Okay, enough wild ideas for now. :-)
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/3699#comment:2>
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