Hi David, | >Recently, however, there has been some interest in using named instance | >declarations in other ways, so perhaps we will see features like this | >creeping into future versions of the language. | | In what kinds of ways? Sounds interesting. I was thinking of a couple of papers from the most recent Haskell workshop. See http://www.cs.uu.nl/people/ralf/hw2001.html for some pointers (the second session). | > module M(C(..), instance C Int, instance C a => C [a]) where ... | | This is the sort of thing I was thinking too. But I would probably want | to extend that to classes and types. For instance | | module M (class Eq a=>C a (...), type A, instance C A, instance C a => C | [a]) | where ... Yes, that's also what I had in mind at the more verbose end of the spectrum (which is not to say that I think it would be a bad thing). A richer, more explicit syntax for export lists might provide some useful documentation and be easier to read than a syntax that leaves you guessing whether C(..) refers to a type or a class. On the other hand, if things start to get too wordy, you might instead want to add a separate notation for describing interfaces. The following is an throwaway syntax, intended only to hint at the basic idea: interface I where class C a where f :: a -> a instance C Int instance C a => C [a] module M implements I where ... ... Start allowing parameterization and other interesting features and this begins to look somewhat like ML style modules (and related systems). All the best, Mark