On 19 February 2015 at 16:29, Erik Hesselink
If I'm reading it correctly, the only example where a fold wouldn't work is <*>, right? And probably conduits, I don't know the types there.
Right, I see three use-cases: * Some things are foldable cleanly like monoids, so you can just mconcat [x,y,z] and that'll be inlined (I think). * Other things like x <|> y is not the same as asum [x,y] due to the additional mempty being introduced. You can also use foldl1 kind of functions, but they are partial and therefore not desirable. * Finally, things like <*>, $=, $, ., #/:& (e.g. in HList/vinyl) can't be folded at all, because the types are different. The third use-case doesn't have a solution that I'm aware of. So this solves that. It also solves the second use-case, which has only a partial (he he) solution. The first use-case is just a bonus. Should I add this clarification to the proposal?