Re: Type signature inside an instance declaration

{-# LANGUAGE ScopedTypeVariables #-} 2008/12/16 Neil Mitchell :

Hi

...

You want to use `asTypeOf`, with a lazy pattern to name a value of type 'a'.

pr xs = "[" ++ pr (undefined `asTypeOf` x) ++ "]" where (x:_) = xs

I prefer:

pr xs = "[" ++ pr (undefined `asTypeOf` head x) ++ "]"

Or even more simply:

pr xs = "[" ++ pr (head x) ++ "]"

I do believe there is some GHC extension that can be turned on to refer to variables like you did, but its not standard Haskell.

Thanks

Neil _______________________________________________ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users

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