The Burning Bridges thread got lots done, but seemed to miss a few things, and didn't even touch on the Numeric classes. The Numeric classes should be fixed at some point, and sooner is better than later. However, it would be a large change and would go nicely with a major version bump in base. 5 is coming up soon. Proposals, ordered from relatively controversial to insanely so (at least IMO): 1. Replace (.) and id from versions from Control.Category in Prelude This is a small change, and has close to the same effect as the Foldable/ Traversable change. The key difference is that this is a much smaller change and there is little current use for the versions from Control.Category However, historically they have seen use with the other lens-ish libraries, and AFAICT are the reason the lenses in `lens` are "backwards", or at least called so my some. 1.2 Use Semigroupoid for (.) and Ob for id instead. Personally, I really like this idea, but I think it would be much more controversial. 2. Move Semigroup into Prelude 2.1 Make Monoid depend on Semigroup. 3. Do something with the Numeric classes. This isn't so much of a proposal as a request for discussion from people more experienced than me, but I still think a general idea if people think that doing *anything* is a good idea would be useful. 3.1 Split each numeric operation into it's own class. Say no to 3.2 and yes here for no hierarchy in them/ConstraintKinds/empty classes. Pros: EDSLs, convenience. Cons: Would be major breakage, would need ConstraintKinds/empty classes to have a hierarchy. 3.2 Hierarchy. the classes are TBD, this is here for a straw poll.