[xmonad] GroupNavigation build error

[Norbert Zeh]

Ivan Lazar Miljenovic [2010.05.11 2137 +1000]:
> Toby Cubitt <tsc25 at cantab.net> writes:
> 
> > Hi,
> >
> > I'm getting build errors in the new GroupNavigation module when compiling
> > xmonad-contrib. This is with the latest xmonad and xmonad-contrib darcs
> > checkout (via the darcs ebuilds on Gentoo), with GHC 6.10.4. (If I've
> > missed any other relevant information, please let me know.)
> >
> > Is this a problem with my GHC version, or my installation of some haskell
> > library, or is it a bug in GroupNavigation?
> 
> Oh-oh.... looks like filter was only added to Data.Sequence as part of
> containers-0.3, which comes with GHC 6.12.

Oops.  I just submitted a patch adding this module to xmonad-contrib.
I'm running arch linux, which comes with GHC 6.12 and never bothered to
check whether there are any problems with older GHC versions.  Sorry.

One way to "fix" this would be to expect everyone running darcs xmonad
to use the latest version of containers, but I'm not sure that's
reasonable.  Another alternative I see is to use CPP to include
home-brewed versions of filter and breakl directly in GroupNavigation if
the detected GHC version is < 6.12.  Any suggestions from the people
with authority (Don, Spencer, Adam, ...) as to what the preferred
solution is?

- Norbert