Adding fromThese and toThese functions

[subttle]

Hi again, I realize you already have a function named toThese unfortunately, so this would be a breaking change, but I do believe what I'm proposing is the proper move all other things considered equal. If you'll notice in similar data types, such as Smash, one has the case-analysis/eliminator smash and then the toSmash and fromSmash functions. Similarly for Wedge, one has the case-analysis/eliminator wedge and then the toWedge and fromWedge. And soon enough there should be the same for Can, they have the case-analysis/eliminator and then once they bring in the These type they could then in theory write the missing toCan and fromCan:

-- Data.Can
toCan ∷ Maybe (These a b) → Can a b
toCan = maybe Non (these One Eno Two)

fromCan ∷ Can a b → Maybe (These a b)
fromCan = can Nothing (Just . This) (Just . That) (curry (Just . uncurry These))

By the way I'm just speculating, I don't speak on behalf of their project, so I hope I'm not giving that impression!
Back on topic, These already has the case-analysis/eliminator of course, and I think it could also use:

-- Data.These
toThese   ∷ Either (Either a b) (a, b) → These a b
toThese   = either (either This That) (uncurry These)

fromThese ∷ These a b                  → Either (Either a b) (a, b)
fromThese = these (Left . Left) (Left . Right) (curry (Right . uncurry (,)))

Now I am aware that the Either makes it so that these functions could be written in multiple ways but my argument is that the case-analysis has always been done in the order in which the data type is defined (c.f. maybe, bool, either, etc.), so it would make sense to use the above definitions because they are in keeping with this tradition because as you know These is defined:

data These a b = This a | That b | These a b

So it makes sense to have a normal form with the sum first and the product after. At any rate, sorry for the rant; it is okay if you don't like my suggestion I won't be offended if you close the ticket and move on, but I decided to share just in case you are interested, in which case let me know if you would like a pull request.

Thank you for your time and consideration. And thanks again for all your hard work on this excellent package!

[phadej]

fromThese follows fromMaybe naming convention.

Converting to/from nested Eithers. I don't know. Does that occur in practice?

I mean. I'm not excited by random abstract non-sense. There have to be a practical purpose, an application of an idea.

Also naming: if it's in Data.These, it should be fromEitherEither and toEitherEither (or something, EitherEither is far from excellent either). c.f. Data.Map.fromList. Data.These.fromThese reads weird (as weird as Data.Smash.fromSmash).

[subttle]

fromThese follows fromMaybe naming convention.

Hm, I would think something along the lines of toTuple (or toPair or paired), or something involving "default" in the name would be more fitting but I can also see the wisdom behind your current naming convention.