Tree.Build_increasing
type ('k, 'v, 'w) t
val empty : ('k, 'v, 'w) t
val add_exn : ('k, 'v, 'w) t -> comparator:('k, 'w) Base__.Comparator.t -> key:'k -> data:'v -> ('k, 'v, 'w) t
val to_tree : ('k, 'v, 'w) t -> ('k, 'v, 'w) t