7 May
2018
7 May
'18
11:58 p.m.
On Mon, May 7, 2018 at 11:45 PM, Clinton Mead
instance {-# OVERLAPPABLE #-} Num x => C x where ... instance {-# OVERLAPPING #-} C Int where ...
is completely legal, and the instance used depends on context.
This is an issue with overlapping instances, but already GHC allows it. I don't think what I'm proposing is any worse to what's already legal.
Int can be verified as more specific than "matches any type". Two instance heads differing *only* in context cannot. -- brandon s allbery kf8nh sine nomine associates allbery.b@gmail.com ballbery@sinenomine.net unix, openafs, kerberos, infrastructure, xmonad http://sinenomine.net