22 Jun
2011
22 Jun
'11
1:05 p.m.
Yay! This is very exciting :-) Edward Excerpts from Simon Peyton-Jones's message of Wed Jun 22 12:57:28 -0400 2011:
Friends
I have long advertised a plan to allow so-called superclass equalities. I've just pushed patches to implement them. So now you can write
class (F a ~ b) => C a b where { ... }
This email is just to encourage you to try them out.
Currently this is just in the HEAD git repository. It'll appear in GHC 7.2, a release we are now actively preparing. But the feature isn't heavily tested (since it didn't exist until today), so I'd appreciate people trying it out.
Thanks
Simon