Proposal: Add concatMapM function (#2042)

[Neil Mitchell]

Hi

> Maybe the
> proposal should rather be to remove concatMap, for it is merely a
> 3-character shorter version of concat . map...

Wrong, its a 5-character shorter version of (concat . map). It's those
brackets that I appreciate the removal of.

> Is concatMapM vs concat <$> mapM really such an improvement?

Yes. It's 7 characters shorter than that. With 7 characters I could
wipe my entire hard drive, those characters matter!! :-)

Thanks

Neil