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On Jun 7, 2018, at 9:14 PM, David Feuer wrote:

I'd be much more interested in Traversable1. Why only propose Foldable1?

Merging Apply/Semiapplicative into base is a much bigger move as it is a step towards making it a superclass of Applicative, and that will AMP levels of code. You need it for Traversable1/Semitraversable to make sense. On the other hand Semifoldable is a concept you can ignore until you start using semigroups more. The community has already paid the price for refactoring their monoids. This gives them some benefit they can reap from pain already borne. -Edward

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On Thu, Jun 7, 2018 at 3:12 PM, Daniel Cartwright wrote: For those of you unfamiliar with 'Foldable1', it is a typeclass for nonempty foldable structures, that centres around Semigroup instead of Monoid. I have made a differential on Phabricator for the change here: https://phabricator.haskell.org/D4812

Some discussion at the following links also:

https://ghc.haskell.org/trac/ghc/ticket/13573

https://www.reddit.com/r/haskell/comments/8p531d/ann_safefoldable_safe_wrapp...

https://github.com/ekmett/semigroupoids/issues/49

Note: foldl1 and foldr1 are currently typeclass methods of 'Foldable' and not 'Foldable1', and even though I think they should be, they probably (and shouldn't) be removed in this change, though I hope that eventually they can be moved to Foldable1.

Foldable1 is also unfortunately named due to the suffix '1' being connotated with the conventions surrounded Data.Functor.Classes (Show1, Eq1, etc.). If this naming is seen as sufficiently unfortunate/confusing because of that, then perhaps the name should be changed to something like 'SemiFoldable'. The name change would most likely have to be made in 'semigroupoids' first if that is the case.

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* Foldable1 -> Semifoldable * Bind -> Semimonad * Apply -> Semiapplicative What other changes are required? On Fri, Jun 8, 2018 at 5:20 AM, Edward Kmett wrote:

I’m generally on board with doing this proposal, but on a pretty slow time table. Why? There is an active change I want to make to the API of semigroupoids that will require a major version bump and would affect the API for Foldable1 among other classes in the library.

The change is more or less the move to calling it Semifoldable, and refactoring Bind and Apply into Semimonad and Semiapplicative to enable users to find prior literature on the ideas behind them.

This will require a major version bump on the semigroupoids package and I’d like to see the dust settle on that before we proceed with anything that as it involves over 100 downstream dependencies having to move. Fortunately I wrote about half of them. Unfortunately, I’m doing a lot of travel for the next couple of months so it may be a bit of a community effort to get everything patched over once we decide to pull the trigger.

I prefer to make big API changes far outside of base. They are much more expensive to make after things merge in.

-Edward

On Jun 7, 2018, at 9:12 PM, Daniel Cartwright wrote:

For those of you unfamiliar with 'Foldable1', it is a typeclass for nonempty foldable structures, that centres around Semigroup instead of Monoid. I have made a differential on Phabricator for the change here: https://phabricator.haskell.org/D4812

Some discussion at the following links also:

https://ghc.haskell.org/trac/ghc/ticket/13573

https://www.reddit.com/r/haskell/comments/8p531d/ann_ safefoldable_safe_wrappers_for_nullpartial/

https://github.com/ekmett/semigroupoids/issues/49

Note: foldl1 and foldr1 are currently typeclass methods of 'Foldable' and not 'Foldable1', and even though I think they should be, they probably (and shouldn't) be removed in this change, though I hope that eventually they can be moved to Foldable1.

Foldable1 is also unfortunately named due to the suffix '1' being connotated with the conventions surrounded Data.Functor.Classes (Show1, Eq1, etc.). If this naming is seen as sufficiently unfortunate/confusing because of that, then perhaps the name should be changed to something like 'SemiFoldable'. The name change would most likely have to be made in 'semigroupoids' first if that is the case.

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