MLton 20210117

# MLtonMonoArray

    signature MLTON_MONO_ARRAY =
       sig
          type t
          type elem
          val fromPoly: elem array -> t
          val toPoly: t -> elem array
       end

- type t

  type of monomorphic array

- type elem

  type of array elements

- fromPoly a

  type cast a polymorphic array to its monomorphic counterpart; the argument and result arrays share the same identity

- toPoly a

  type cast a monomorphic array to its polymorphic counterpart; the argument and result arrays share the same identity