DData modules

Ross Paterson ross at soi.city.ac.uk
Thu Jan 13 09:56:31 EST 2005

On Thu, Jan 13, 2005 at 02:13:08PM +0000, Malcolm Wallace wrote:
> Ross Paterson <ross at soi.city.ac.uk> writes:
> > Also, these modules import Data.Monoid, which contains the non-H98 instance
> > Monoid (a -> a), making it (and these) non-portable.
> In what sense is
>     instance Monoid (a -> a)
> not Haskell'98?  It looks perfectly OK to me.  Is it because the two
> type variable arguments to (->) are the same?

Yes -- the Report even makes an example of instance C (a,a).
But it seems that nhc98 implements this extension.

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