[Haskell-cafe] ANN: Data.Monoid.First and Data.Monoid.Last are here to stay

[Simon Jakobi]

Hi!

I'm happy to report that the planned deprecation of
Data.Monoid.{First,Last} [0] has finally been scrapped [1].

The original motivation for removing these newtypes of Maybe was to
resolve the name conflict with Data.Semigroup.{First,Last} [2].

Unfortunately, while implementing the deprecation, I ended up
discovering a whole host of problems with the suggested migration to
(Maybe Data.Semigroup.First) and (Maybe Data.Semigroup.Last), which I
have attempted to summarize in my email to the libraries mailing list
[3].

I would like to thank everyone who contributed to the discussion of
the matter, the CLC, and also everyone who pushed me to finally get
the matter resolved. :)

Cheers!
Simon

[0] http://hackage.haskell.org/package/base-4.14.0.0/docs/Data-Monoid.html#t:First
[1] https://gitlab.haskell.org/ghc/ghc/-/commit/f44d7ae08442ae6227db37cacc97fe0def8017c5
[2] https://mail.haskell.org/pipermail/libraries/2018-April/028712.html
[3] https://mail.haskell.org/pipermail/libraries/2020-April/030357.html