[Haskell-cafe] MRP, 3-year-support-window, and the non-requirement of CPP

Edward Kmett ekmett at gmail.com
Sat Oct 10 19:13:26 UTC 2015

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

> 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

Most of the patches to go -Wall clean looked like

+#if __GLASGOW_HASKELL__ < 710
import Control.Applicative
import Data.Monoid

Maybe 10% were more complicated.

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