Tony Morris

Fair enough - what did I miss in my (nasty) bit of code? Doesn't it expose exactly the fact that global uniqueness is not guaranteed by ghc? Who's got the bigger type class implementation is another debate entirely and not at all the point I was making, sorry if it was unclear

The argument is practical Write Haskell; never use orphan instances. This is achievable with little/no penalty Write Scala; never use orphan instances. With this commitment, it's difficult & there's no sweet spot Scala does not have type-classes in any general practical sense

The separate discussion that you're answering to is interesting though. I'd like to know how you define a type class, and in which way that definition invalidates Scala's encoding of them. This is neither a challenge nor sarcasm. I'm genuinely interested.

It's a rabbit hole! Happy to go there though.

I'm genuinely interested and ready to go down that rabbit hole, but do not mean to presume that you have the time to.

We can start with a shortcut! Have you seen the attempts at a Scala type-class hierarchy, dating back to 2005, using implicits and sub-typing, and still not getting it right? i.e. there is still not a usable type-class hierarchy, 15 years later.

Are we limiting type class to categorial abstractions here? Or do you mean any type class, even ones such as `Eq`, for example?