Hi Sophie,
In your proposal draft, I am missing the rationale part. Yeah, I'm still writing it - I definitely need to expand that a bit mor.
Do we need *all* of these classes in base in order to desugar proc? Can you demonstrate why they are needed? Or will something simpler suffice?
I think I might remove the binoidal class, and remove the PFunctor/QFunctor classes - I included them because I usually find finer grained class hierarchies to be more tasteful; but it probably would make it more frustrating to implement an arrow, for example. With SMC classes, proc notation can be desugared to remove a LOT of calls to arr, which allows more fine-grained RULES optimisations to take place, and additional work such as the ModalTypes extension in Adam Megacz Joseph's thesis to be much more straightforward.