Cubicle 1.1.2 documentation and source : Variable.extra

let extra_vars vs1 vs2 =
  let rec aux dif vs1 vs2 = match vs1, vs2 with
    | [], [] -> dif
    | _::_, [] -> vs1
    | [], _::_ -> dif
    | a::ra, b::rb -> aux dif ra rb
  in
  aux [] vs1 vs2