Instances in libraries (e.g., Control.Monad)

Simon Marlow
Fri, 15 Nov 2002 15:58:33 -0000

I said, accidentally:
> IMO, given the current design of Haskell 98, instances should be
> considered to be global.  There is only room for one instance for each
> type/class pair in any program (including the libraries). =20
> Otherwise the
> library documentation has to publish for each module, a list=20
> of all the
> instances defined by it and all modules below it in the=20
> dependency tree.
> I think this is just silly.

Of course, the library documentation still has to publish the list of
modules from which an instance can be imported.  I meant to delete the
above paragraph before sending the msg.  Please disregard.