Type signature inside an instance declaration

[Kwanghoon Choi]

Many thanks for your helps.

Kwanghoon

On Tue, Dec 16, 2008 at 11:22 PM, Thomas Schilling
<nominolo at googlemail.com>wrote:

> {-# LANGUAGE ScopedTypeVariables #-}
>
> 2008/12/16 Neil Mitchell <ndmitchell at gmail.com>:
>  > 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
> > _______________________________________________
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> > Glasgow-haskell-users at haskell.org
> > http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
> >
>
>
>
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