Replying to myself as I thought of an example from my own past which is relevant. After discovering the eye-opening expressivity of functional programming year

Replying to myself as I thought of an example from my own past which is relevant. After discovering the eye-opening expressivity of functional programming years ago with Dylan and Haskell, I had a substantial project in javascript. I found JS supported first class closures and lambdas, which allowed me to make iterators. The novelty was they were iterators not over lists but over trees (DOM trees in this case but of course any tree could be made iterable). I understood there would be a learning cost for anyone who took over from me so I left plenty of docs and pointers. It would not be a small cost either, my successors would have to learn to think differently, at a higher level and possibly rather alien (to them) way. But was it worth the cost, bloody hell yes! Not having that iterable and rather declarative abstraction over DOM trees would have greatly bloated the code and consequently brought in bugs by the bagful. I would do in a couple of lines what would have taken half a page to do, in many locations. So it had a human cost but if you could overcome that, a seriously huge human benefit.