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OCaml 4.14.2 on FreeBSD 15.0-RELEASE

Table of Contents

1. Environment

uname -a

FreeBSD nexus 15.0-RELEASE FreeBSD 15.0-RELEASE releng/15.0-n280995-7aedc8de6446 GENERIC amd64
Tool Version Source
OCaml 4.14.2 pkg install ocaml
opam 2.4.1 pkg install ocaml-opam
dune not installed opam install dune
zarith 1.13 pkg install ocaml-zarith
findlib 1.9.6 pkg install ocaml-findlib

2. Installation

pkg install ocaml ocaml-opam
opam init --bare
opam switch create 4.14.2
opam install dune base64 alcotest

dune is not in FreeBSD ports — it must come from opam.

3. Lessons from the Transform Pipeline

The OCaml implementation at aygp-dr/transform-tool-ocaml exposed three spec gaps:

  1. Chain parser: parsed :d at chain level, not per-step. Pattern matching on character ranges was clean, but the string splitting required manual buffer iteration (no Str in stdlib).
  2. XOR codec: treated as involution (f(f(x)) = x at byte level). The spec requires hex output, making it a bijection.
  3. reverse_pipeline: flipped direction on involutions. Harmless in OCaml (same function in both record fields) but wrong per spec.

All three were fed back into the spec.

3.1. What OCaml does well

Pattern matching for character-level codecs: 

let rot13_char (c : char) : char =
  match c with
  | 'A' .. 'M' -> Char.chr (Char.code c + 13)
  | 'N' .. 'Z' -> Char.chr (Char.code c - 13)
  | 'a' .. 'm' -> Char.chr (Char.code c + 13)
  | 'n' .. 'z' -> Char.chr (Char.code c - 13)
  | _ -> c

string option for decode failure forces every call site to handle it.

4. Related Work