OCaml GADTs to ReasonML

reasonml_gadts.re

/* ReasonML equivalent to OCaml's GADTs:
type 'a t =
  | Array : 'a array -> 'a t
  | Bytes : bytes -> char t

let length (type el) (t:el t) = match t with
  | Bytes b -> Bytes.length b
  | Array a -> Array.length a

*/

type t('a) =
  | Array(array('a)): t('a)
  | Bytes(bytes): t(char);

let length (type el, t: t(el)) =
  switch (t) {
    | Array(x) => Array.length(x)
    | Bytes(b) => Bytes.length(b)
  };