Drastic Prelude changes imminent

[Malcolm Wallace]

On 27 Jan 2015, at 20:18, Eric Mertens wrote:

> I've been keeping up with the changes to GHC and specifically this BBP for quite some time now, so none of this is coming as a surprise.
> 
> I don't think it's fair to characterize any of these changes as a surprise. The discussion has been open and the implementations have been visible for a long time now.

If we are comparing experiences, I was aware of the Applicative/Monad changes that were going into the Prelude, and have already fixed my packages that required changes (I long for the day when a release of ghc does _not_ break existing libraries!), but since I am not a regular reader of all the mailing lists, I was totally unaware that the Foldable/Traversable stuff was even proposed for the Prelude, never mind had actually made it to a release.  The first I knew it was in Prelude was in the middle of last week, when someone reported code that would not compile with ghc-7.10rc1 because of it.  Everyone I work with was horrified to hear that something so essential as the Prelude was being changed so thoroughly without their being aware of it either.

I do think that the current social mechanisms for changing the Haskell base library are less than ideal.  It sometimes feels like someone can send a message to a mailing list with a "bright idea", and so long as only a few people see it, and those that do see it do not object, the proposal is automatically accepted.  That would be fine for any library _except_ base, which I think ought to be much more stable.

Regards,
    Malcolm