Proposal: Add concatMapM function (#2042)

[Henning Thielemann]

On Tue, 15 Jan 2008, Yitzchak Gale wrote:

> Hi Bulat,
>
> I wrote:
> >> I import only the functions I need from libraries that I don't
> >> own myself to minimize that effect.
>
> Bulat Ziganshin wrote:
> > i think that the better way will be to put all these functions into
> > extralibs bundled with ghc. this will allow me to control which
> > concrete version of lib i import and therefore which set of functions
> > i've used.
>
> Yes. But you still need to put the new functions in the
> right place in the module hierarchy. How do we do that?
>
> For each module included in the bootlibs, would
> you have also Path.To.Module.Extra? That would
> be annoying. And it wouldn't even solve the problem:
> if you use Extra even once, you would go back
> to the same situation.

I collected some points at
  http://www.haskell.org/haskellwiki/Import_modules_properly