On Thu Jun 1 12:44:32 UTC 2017, Anthony Clayden wrote:

...

For example, consider the simple chain:

class C t u where f :: t -> u instance C Int Int where f = M else C t u where f = N

Ah, silly me. There's a neater way to achieve that.

I think Instance Guards both have less lexical clutter, and help the compiler see what's coherent:

instance C Int Int where f = M instance C t u | (t, u) /~ (Int, Int) where f = N

AntC