Add functional helpers

[rullzer]

In some places more functional programming would make sense. See https://medium.com/ifixit-engineering/functional-programming-with-php-generators-837a6c91b0e3 for example.

The library https://github.com/nikic/iter already does a nice job at wrapping most of it.

Of course we should only use it when it makes sense. But we seem to already use use array_map, array_filter etc in a lot of places. So it might make sense to try to move some things to generators.

CC: @ChristophWurst @MorrisJobke @juliushaertl @icewind1991 for some brainstorming

[nextcloud-bot]

GitMate.io thinks possibly related issues are #363 (Add Snap Information), #10967 (Add fix response), #5788 (add catalan language again), #9320 (Add revision number), and #74 (Add Automatic Tagging).

[ChristophWurst]

👍 from my side. Having some functional helpers would be awesome! As a start we could add such a lib to the 3rdparty repo for 15 or 16, see how well that works and if we like it we can re-export those features via OCP.

[szaimen]

I suppose this is still valid?

[ChristophWurst]

yes, still relevant