foldable flexible bridges (putting foldable+traversable in prelude) Re: Burning bridges

[Conrad Parker]

On 24 May 2013 08:27, John Lato <jwlato at gmail.com> wrote:
> I agree with Mark and wren; it would be better to fix several of these
> issues at once.  I think it would be helpful to know how frequently
> community members would tolerate breaking changes like this.  For myself, I
> think 2-4 years seems right, with 2 on the fast side.  My impression is
> there's a lot of support for rolling breakages, but maybe that's not the
> case?

I'd much prefer to have all these little things (type hierarchy
cleanup, prelude generalisation) lumped together:
  * available in a ghc release but off-by-default; that way library
authors and commercial users can test the changes without hacking ghc
  * default in the following ghc release, but disableable by a flag
  * with a document explaining how to transition code

I expect most of the transitioning advice would be pointing out which
lines to remove from imports and custom instances, and I'd prefer to
do all that once asap rather than once every 6 months for the next few
years.

Conrad.