[RandomThoughts3]

No, not this. You are doing a map. A traversal of a data collection is not a map but a fold. The exemple in the article is specifically about collection which you would do by consing to a list (mostly free once optimised) in a fold_left (so tail call optimised to a loop). See my other comment.

Also, List.map is not optimised in Ocaml. It uses a naive implementation and not a tail call. You have to use rev_map to get good perf.

[derdi]

> A traversal of a data collection is not a map but a fold. The exemple in the article is specifically about collection which you would do by consing to a list (mostly free once optimised) in a fold_left (so tail call optimised to a loop).

The exact wording in the article is "let's say you're iterating over some structure and collecting your results in a sequence". You are interpreting a lot into this. Also, your description is of a map (reversed, and expressed as a fold). Anyway, where is your benchmark?

> Also, List.map is not optimised in Ocaml. It uses a naive implementation and not a tail call.

You are again contradicting yourself. Previously you were praising OCaml's optimization capabilities and now you are questioning them. Specifically in a case where there is a magic optimization that is explicitly motivated by List.map: https://ocaml.org/manual/5.2/tail_mod_cons.html . A magic optimization implemented using, guess what, mutation.