> > Actually I think you would be better off with a class like
> > this:
> >
> > class (Eq key, Ord key) => Dictionary dict key where
> > delete :: key -> dict dat -> dict dat
> > search :: key -> dict dat -> (key, SearchResult dat, dict dat)
> > searchList :: [key] -> dict dat -> ([(key,SearchResult dat)],dict dat)
>
> Ok, I did not reconize this solution, it seems to me the (nearly) proper one.
> But why not write:
>
> class => Dictionary dict where
> delete :: (Eq key, Ord key) => key -> dict key dat -> dict key dat
> ...
>
> So one could avoid multiparamter classes at all. The two types key and dat
> should be inferred by the type of dict (which is expressed by 'dict key dat'). I
> can't think about a dictionary where key or dat are not associated with dict.
Yes, that's ok too. You might find my paper "Bulk types with class"
somewhat relevant.
http://www.dcs.gla.ac.uk/~simonpj/papers.html
Simon
