GHC 7.10 regression when using foldr

Kim-Ee Yeoh ky3 at
Tue Jan 20 14:00:52 UTC 2015

On Tue, Jan 20, 2015 at 6:45 PM, Edward Kmett <ekmett at> wrote:

> I can at least say that the incident rate for cases seems to be very low,
> especially when it is contrasted against the pain users have had with using
> the existing Foldable/Traversable imports where virtually everything in
> them collided with less useful versions of the same combinator (e.g. mapM)
> from the Prelude that a dozen other modules (e.g. Control.Monad and
> virtually every module in mtl) insisted on re-exporting, making it a game
> of whack-a-mole to try to hide them.

There are few reports because the change hasn't affected the dark majority
yet. RC builds are used by a tiny fraction. There's a long tail of users
still on 7.6, 7.4, 7.2, and 6.x.

The whack-a-mole game needs only to be played once and the results shared
among those relying on the abstractions. Was that route ever explored?

The FTP discussion needs to be re-opened. And it will be, eventually.

-- Kim-Ee
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