test.ml

module RRef : RREF = struct
  type snap = SNil : snap | SCons : 'a * 'a ref * snap -> snap

  type reflist = RNil : reflist | RCons : 'a ref * reflist -> reflist

  let cell_list = ref RNil

  let rref x =
    let r = ref x in
    cell_list := RCons (r, !cell_list);
    r

  let snapshot () =
    let rec loop = function
      | RNil -> SNil
      | RCons (r, rest) -> SCons (!r, r, loop rest) in
    loop !cell_list

  let rec reload = function
    | SNil -> ()
    | SCons (x, r, rest) -> r := x; reload rest
end