[Haskell-cafe] Scraping boilerplate deriving?

[Miguel Mitrofanov]

  class (A x, B x, C x, D x) => U x

?

14.09.2010 12:24, Kevin Jardine пишет:
> I have a set of wrapper newtypes that are always of the same format:
>
> newtype MyType = MyType Obj deriving (A,B,C,D)
>
> where Obj, A, B, C, and D are always the same. Only MyType varies.
>
> A, B, C, and D are automagically derived by GHC using the
>
> {-# LANGUAGE GeneralizedNewtypeDeriving #-}
>
> feature.
>
> I would like to use some macro system (perhaps Template Haskell?) to
> reduce this to something like
>
> defObj MyType
>
> I've read through some Template Haskell documentation and examples,
> but I find it intimidatingly hard to follow. Does anyone has some code
> suggestions or pointers to something similar?
>
> Alternatively, is there any way in standard Haskell to define some
> kind of union class:
>
> U = (A, B, C, D)
>
> and then using
>
> newtype MyType = MyType Obj deriving U
>
> which would at least be shorter?
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