[Hugs-users] Network.CGI missing in Hugs

Ross Paterson ross at soi.city.ac.uk
Wed Jan 10 18:21:07 EST 2007

On Wed, Jan 10, 2007 at 09:47:04PM -0000, Claus Reinke wrote:
> Bjorn Bringert wrote:
> >The bottom line is that the instance:
> >
> >instance (MonadTrans t, MonadCGI m, Monad (t m)) => MonadCGI (t m) where
> >
> >needs both overlapping and undecidable instances, doesn't work in  
> >Hugs, and probably won't be Haskell'-compatible. 
> but overlapping instances were also pioneered in Hugs!-)
> there are differences, eg,  in how FDs combine with overlaps, or how scoped 
> type variables in instances are interpreted, but Hugs has both unlimited 
> and overlapping instances.

Yes, Hugs accepts this one with +o.  Hugs does have additional
restrictions on overlapping instances that GHC defers to their point
of use, but this particular case is OK, because one of the overlapping
instances is a substitution instance of the other.

More information about the Hugs-Users mailing list