On Monday, 19 December 2016 at 17:44:29 UTC, Andrei Alexandrescu
Take a look e.g. at
https://dlang.org/phobos-prerelease/std_algorithm_iteration.html. Examples now have "Edit" and "Run" buttons that allow you to play with them online and see what they output. Changes for the ddox version forthcoming.
Many thanks to Sebastian Wilzbach who took this to completion,
and to Damian Ziemba for working on the online compiler code!
I would like to add that this is in an experimental/testing stage
and hopefully will get stable with the next release ;-)