Re: Diagonalization/ dupe for monads and tuples?

I’m not sure how fromMaybe relates here. Could someone explain? For the anti-categorical folks who dislike codiag or related names like trace (in linear algebra trace is the sum of the diagonal of a matrix as a scalar, an apt analogy I think), another name that I think is descriptive is collapse Names bandied about so far: Dedup Codiag Fromeither Things I mentioned above : trace and collapse Zooming out though, this operation is equiv to “either id id”, so I don’t really see how inventing a new name for this specific tiny snippet really helps anyone. On Thu, Sep 17, 2020 at 8:54 AM chessai wrote:

My instinct about fromEither's type was the same as Carter's, and I had to remind myself of fromMaybe. I like the name fromEither overall. Seems to fit well with precedent and is straightforward enough.

On Thu, Sep 17, 2020, 07:45 Oliver Charles wrote:

...

You may wish to compare with fromMaybe then, which probably also doesn't have the type you'd expect :) The type you have there is more like bifoldMap

On Thu, 17 Sep 2020, at 1:42 PM, Carter Schonwald wrote:

I’d expect fromEither to be Either a b -> (a-> c )-> (b-> c) -> c

Nothing about the name fromEither is suggestive of the Either a a type

On Thu, Sep 17, 2020 at 3:45 AM Oliver Charles wrote:

Regardless of having a more abstract version, I'm +1 on Jon's suggestion, and those names. fromEither is something I have reached for many many times and been surprised it's not within arms reach.

On Thu, 17 Sep 2020, at 7:16 AM, Jon Purdy wrote:

I’m strongly for these:

Data.Tuple.dup :: a → (a, a)

Data.Either.fromEither :: Either a a → a

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