Arguably, first class higher order function (and immutability) is defining characteristics of functional programming. Although, I don't think the functional/ i

Arguably, first class higher order function (and immutability) is defining characteristics of functional programming. Although, I don't think the functional/ imperative is necessary a good axis for categorizing languages. There are potentially more differences between Clojure/Ocaml than Python/Clojure, for example.