[xmonad] GroupNavigation build error

[Norbert Zeh]

Adam Vogt [2010.05.11 1308 -0400]:
> * On Tuesday, May 11 2010, Ivan Lazar Miljenovic wrote:
> 
> >Norbert Zeh <nzeh at cs.dal.ca> writes:
> >> 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?
> >
> >The source of filter seems to be straightforward; maybe just copy it
> >directly and not worry about CPPing?
> >
> >-- | /O(n)/.  The 'filter' function takes a predicate @p@ and a sequence
> >-- @xs@ and returns a sequence of those elements which satisfy the
> >-- predicate.
> >filter :: (a -> Bool) -> Seq a -> Seq a
> >filter p = foldl (\ xs x -> if p x then xs |> x else xs) empty
> 
> Right, so we could substitute the definitions when the the containers
> version that cabal specifies is too low (see attached ugly patch).
> 
> containers-0.3.0.0 should build with older GHCs. It would be much easier
> to manage if we could just require a newer containers: maintaining those
> macros is a fair amount of work. Is that allowed, or is it too great a
> concern that this adds one more dependency to fetch for users with older
> GHCs?

Indeed, requiring the newer containers is the cleanest solution, but
your last question is exactly the concern I had about this solution.
Don, Spencer: any opinion on this one?

N.