Discussion: forM for Data.Set

George Wilson george at wils.online
Sun Jan 12 21:35:19 UTC 2020

Adding `traverse` and `for` to Data.Set seems like a good idea.

I am not convinced about adding mapM and forM if there's no
performance benefit to those versions. I'd rather not see that
redundancy proliferate without good reason. In base, I would like to
see those functions reduced to aliases per this thread [1], but that's
waiting on [2].

[1] https://mail.haskell.org/pipermail/libraries/2015-May/025708.html
[2] https://gitlab.haskell.org/ghc/ghc/issues/10071


On Fri, 10 Jan 2020 at 10:40, hasufell at posteo.de <hasufell at posteo.de> wrote:
> This was posted a year ago already, but without many comments:
> https://mail.haskell.org/pipermail/libraries/2019-January/029335.html
> So after cleaning up the PR a bit, adding tests and benchmarks, let's
> give it another go.
> PR is at: https://github.com/haskell/containers/pull/592
> New functions are: forM, mapM, for, traverse
> This follows the other Data.Set exported functions, overwriting Prelude
> ones like foldr etc, so I think that's exactly what we want.
> Cheers,
> Julian Ospald
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