bsrefmt --parse=re --print=ml https://github.com/joelonsql/reason-re-nfa/blob/master/src/Letter2Set.re

Letter2Set.ml

(*

    ocamldep .Re0.eobjs/Letter2Set.ml.d (exit 2)
(cd _build/default && /Users/joel/.opam/ocaml-base-compiler/bin/ocamldep.opt -modules -impl Letter2Set.ml) > _build/default/.Re0.eobjs/Letter2Set.ml.d
File "Letter2Set.ml", line 11, characters 4-8:
Error: Syntax error

*)

module Pair =
  struct
    type t = (Letter.t* Letter.t)
    let compare ((_,w),(_,x)) ((_,y),(_,z)) =
      match Int32.compare w y with | 0 -> Int32.compare x z | i -> i
  end
include Set.Make(Pair)
let (<+>) = union
let (>>=) m k = LetterSet.fold (fun x  -> fun s  -> union (k x) s) m empty
  [@@ocaml.doc " Flat map "]
let <*>: LetterSet.t -> LetterSet.t -> t =
  fun l  -> fun r  -> l >>= (fun x  -> r >>= (fun y  -> singleton (x, y)))
  [@@ocaml.doc
    " Cartensian product, i.e. all elements in l combined with all elements in r "]
let to_string l2s =
  String.concat " "
    (List.rev
       (fold
          (fun (letter1,letter2)  ->
             fun l  ->
               ((Letter.to_string letter1) ^ (Letter.to_string letter2)) :: l)
          l2s []))
let example letter1 letter2 = singleton (letter1, letter2)
let test () =
  let abc = example (Letter.example ['a'] 0) (Letter.example ['b'; 'c'] 1) in
  assert ((to_string abc) = "a<sub>0</sub>[bc]<sub>1</sub>");
  (let a = LetterSet.example ['a'] 0 in
   let bc = LetterSet.example ['b'; 'c'] 1 in
   let abc' = a <*> bc in
   assert (equal abc abc');
   (let abc'' = a >>= (fun x  -> bc >>= (fun y  -> singleton (x, y))) in
    assert (equal abc abc'')))