Module type Binary_searchable_intf.Binary_searchable.Indexable

module type Indexable = Binary_searchable_intf.Indexable

type elt 
type t 
val get : t ->
int -> elt
val length : t -> int
module For_test: sig .. end
To implement the test provided by Binary_searchable, we need to be able to construct t with two different values small < big.