val random_split : ?random_state:Core.Random.State.t ‑> 'a array ‑> p:float ‑> 'a array * 'a arraymakes a random split & subset of an array; p (the fraction that you want to split) is
constrained to be 0, 1. Note that the length of the first array will be the closest
integer to the fraction you desired, meaning that each element is NOT selected with
probability exactly p.
val random_sub : ?random_state:Core.Random.State.t ‑> 'a array ‑> p:float ‑> 'a array