[rydel]

There are many definitions of FP. IMHO the “no side effects” is the best one. Even Clojure is functional, but partially IMHO, bc it is for JVM which has not been design for FP. And my definition is not an arbitrary one. This is the most broadly one I think. But when you use same word in different contexts, then the word might have different meaning.

[pjmlp]

Which means OCaml, Common Lisp, Scheme, F#, SML are out of the game as FP languages according to you.

[rydel]

Is I wrote: IMO these language are not fully functional. TCO/TCE is crucial for operations on tree like data structures. And also as I wrote: it all depends in which context we are talking to. Scheme specification makes it clear that TCO/TCE is required. If I am not wrong, F# is the same thing as Scala, but in .Net world(?) - Scala cannot be treaded as clear functional, because it is for JVM which was not designed for functional programming. Surely, many languages can have more or less functional functionalities, but having a subset of properties which defines what is functional, cannot be treated as functional in the full sense.