On Tue, Oct 6, 2015 at 3:02 PM, Malcolm Wallace <malcolm.wallace@me.com> wrote:

On 6 Oct 2015, at 17:47, Herbert Valerio Riedel wrote:
> At the risk of stating the obvious: I don't think it matters from which
> group a given argument comes from as its validity doesn't depend on the
> messenger.

In that case, I think you are misunderstanding the relevance of Johan's argument here. Let me try to phrase it differently. Some people who can reasonably claim to have experience with million-line plus codebases are warning that this change is too disruptive, and makes maintenance harder than it ought to be. On the other hand, of the people who say the change is not really disruptive, none of them have (yet?) made claims to have experience of the maintenance of extremely large-scale codebases.

Very well. Let me offer a view from the "other side of the fence."

I personally maintain about 1.3 million lines of Haskell, and over 120 packages on hackage. It took me less than a half a day to get everything running with 7.10, and about two days to build -Wall clean. In that first day I actually had to spend vastly more time fixing things related to changes in Typeable, template-haskell and a tweaked corner case in the typechecker than anything AMP/FTP related. In the end I had to add two type signatures.

Most of the patches to go -Wall clean looked like

+#if __GLASGOW_HASKELL__ < 710

import Control.Applicative

import Data.Monoid

+#endif

Maybe 10% were more complicated.

-Edward