Re: traverse_

I have no objection to having the discussion about widening the set of symbols to shave off warts like this in 7.12. -Edward On Tue, Mar 31, 2015 at 10:11 AM, Fumiaki Kinoshita wrote:

I understand the ground. It seems reasonable not to add symbols facilely.

But in this case, the "too specialized" version is exported while more fundamental one is not. Although folks (including me) use mapM_ mostly today, someday we will like to have traverse_, I guess.

2015-03-31 19:41 GMT+09:00 Edward Kmett :

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We deliberately took no more symbols than we needed in 7.10 from Prelude as part of the Foldable/Traversable Proposal. There are multiple combinators in Data.Foldable and Data.Traversable that we do not export. traverse_ is one of them as, strictly speaking, traverse_ was a symbol we didn't have to take.

If we had would anybody have complained any more loudly? Not sure... but it was a deliberate choice to not bring in any symbols into Prelude that weren't already there that weren't part of the definition of a class or needed to define instances that already existed.

-Edward

On Mon, Mar 30, 2015 at 11:33 PM, Fumiaki Kinoshita wrote:

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Well, I see. It'd be nice.

That aside, the absence of traverse_ doesn't seem to be intended (even the documentation for mapM_ says "mapM_ is just traverse_"!)

2015-03-30 16:54 GMT+09:00 Herbert Valerio Riedel :

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On 2015-03-30 at 07:05:56 +0200, Fumiaki Kinoshita wrote:

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I found out that (<>) (in Data.Monoid) is missing, also. It would be nice to reexamine Prelude to export things we want to export.

Fwiw, (<>) was actually left-out as it wasn't required (it's just a an alias for `mappend`), *and* to keep our options open (or at least not make it more difficult) in terms of possible migration-plans available for the case we'd be moving 'Semigroup' to base/Prelude at some point in the future.

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