Re: Bifoldable instance for Map

On 2020-06-03 01:47, Joseph C. Sible wrote:

Isn't the order of elements when you use a Traversable also arbitrary, since trees have depth-first and breadth-first traversals?

Do you mean the order of the effects? Yes, this order isn't specified. The tree structure should stay intact though (including the leaves, which are merely filled with new content). --Andreas

On Tue, Jun 2, 2020 at 9:39 AM Andreas Abel wrote:

...

I think bitraverse makes some sense. If you have a tree with two kinds of leaves, you can effectfully map over it.

bitraverse :: Applicative f => (a -> f c) -> (b -> f d) -> t a b -> f (t c d)

Here, the tree structure stays in place.

However, bifolding is less meaningful because the ordering of elements in the resulting collection (monoid) is somewhat arbitrary. This argument has already been raised in this thread.