I find it hard to warm up to this though. To me the cost seems awfully high in terms of increased complexity. All these crammed complex on-liners must be very hard to understand and maintain, not to mention how difficult it must be to make changes after a while even if you wrote it yourself.
Me too! I'm quite happy to stick with first-class and pure functions. For languages such as c++/java etc I still don't get the requirement for immutable functions - but maybe it's just me and my previous 45+ years of non-functional programming!