Functor MakeHash: hash table generator

Hash tables are hashed association tables, with in-place modification.
signature HashedType =
    type t
    val equal: t -> t -> bool
    val hash: t -> int
The input signature of the functor MakeHash. t is the type of keys. equal is the equality predicate used to compare keys. hash is a hashing function on keys, returning a non-negative integer. It must be such that if two keys are equal according to equal, then they must have identical hash values as computed by hash. Examples: suitable (equal, hash) pairs for arbitrary key types include ((=), Hashtbl.hash) for comparing objects by structure, and ((==), Hashtbl.hash) for comparing objects by addresses (e.g. for reference values or cyclic keys).
signature HASH =
    type key
    type 'a t
    val create: int -> 'a t
    val clear: 'a t -> unit
    val add: 'a t -> key:key -> data:'a -> unit
    val remove: 'a t -> key -> unit
    val find: 'a t -> key -> 'a
    val find_all: 'a t -> key -> 'a list
    val replace : 'a t -> key:key -> data:'a -> unit
    val mem: 'a t -> key -> bool
    val iter: f:(key:key -> data:'a -> unit) -> 'a t -> unit

functor MakeHash(H: HashedType): (HASH with type key = H.t)
The functor MakeHash returns a structure containing a type key of keys and a type 'a t of hash tables associating data of type 'a to keys of type key. The operations perform similarly to those of the generic interface, but use the hashing and equality functions specified in the functor argument H instead of generic equality and hashing.