[challenge] Lazy flatten/avoiding type forward reference with map

[Andrej Mitrovic]

On 11/1/13, David Nadlinger <code at klickverbot.at> wrote:
> I just thought I'd be interested to see what the best solution we
> can find in terms of conciseness is.

Note that I've already asked this in D.learn:
http://forum.dlang.org/thread/mailman.43.1383090512.9546.digitalmars-d-learn@puremagic.com