On Fri, Oct 23, 2015 at 6:07 PM, Charles Durham
I can think of a few properties that folds can honor:
1. Promises to call f on all data (does not have any guarantees on order) 2. Promises to call f on all data in order (like a left fold) 3. Promises to call f "associatively" (perhaps can be formalized as an in order break down of the data into tree structures)
For what concerns traversable functors, traversals enjoy properties of "unitarity" and "linearity" which *might* entail what you are interested in: M. Jaskelioff, O. Rypacek - An Investigation of the Laws of Traversals http://arxiv.org/abs/1202.2919 I have never gone through the details of that very interesting paper: the analysis in section 4 gives some intuition, though. I hope this is related to your questions. Cheers, Matteo