Re: Bifoldable instance for Map

Let me be more specific. Whereas we can get intuition for Foldable from toList :: t a -> [a] we get intuition for Bifoldable from the hypothetical toEitherList :: t a b -> [Either a b] This seems quite reasonable for some types. data Loost a b = Nool | Corns b (Loost a b) | Colns a (Loost a b) But for something like newtype Plist a b = PNil | PCons a b (PList a b) it feels awfully strange. Independent parts of the structure just get lumped together. On Sat, May 30, 2020, 8:33 PM David Feuer wrote:

Let me take that back. I forgot how weird Bifoldable and Bitraversable are for product types and product-like types. Is this instance actually useful for anything, or is it mostly confusing?

On Mon, Apr 13, 2020, 9:46 PM David Feuer wrote:

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I would go as far as to say we don't need to continue the proposal process here. We're doing it.

On Mon, Apr 13, 2020, 9:44 PM David Feuer wrote:

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This seems eminently reasonable to me. We must also be sure to add one to Data.HashMap if that's missing too.

On Mon, Apr 13, 2020, 9:36 PM Joseph C. Sible wrote:

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I'd like to propose a change to the containers package: adding a Bifoldable instance to Map. I briefly mentioned this on Reddit [1] and no obvious problems were brought up. I submitted a PR implementing it [2]. This seems like an obvious and straightforward instance to me. Thoughts?

Joseph C. Sible

[1]: https://old.reddit.com/r/haskell/comments/fsgqd6/monthly_hask_anything_april... [2]: https://github.com/haskell/containers/pull/714 _______________________________________________ Libraries mailing list Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries