Defaults for superclass methods

Ashley Yakeley ashley at
Thu Apr 13 16:23:39 EDT 2006

Simon Marlow wrote:

> If it's not clear which is the right way to go, then yes I guess that
> does rule it out.  Could you summarise the proposals?  If there was a
> clear winner, and it was easy enough to implement, perhaps we can knock
> up a prototype in time.
> The reason being I just hit a case where this would be useful, while
> trying to find a nice way to express extensible exceptions.

If we're going to do this, we should make Functor a superclass of Monad. 
This is a well-known and annoying wart in the standard libraries that 
has not been fixed only because there's no superclass default mechanism.

Ashley Yakeley, Seattle WA

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