Interface with multiple implementations in OCaml

Question

What is the usual way to create an interface in OCaml? It is possible to have an interface with one implementation by creating an interface file foo.mliand an implementation file foo.ml, but how can you create multiple implementations for the same interface?

Answer 1

If you have multiple implementations for the same signature, define your signature inside the compilation block, and not as a compilation block, and (if necessary) the same for modules. Here is an example of this in the standard library: a signature OrderedTypethat describes modules with a type and a comparison function for this type:

module type OrderedType = sig
  type t
  val compare : t -> t -> int
end

set.mli, map.mli ( Set.OrderedType Map.OrderedType, : ). , (String, Nativeint ..). , : , t compare t -> t -> int, . : Set.Make , OrderedType, .

(* All four modules passed as arguments to Set.Make have the signature Set.OrderedType *)
module IntSet = Set.Make(module type t = int val compare = Pervasives.compare end)
module StringSet = Set.Make(String)
module StringSetSet = Set.Make(StringSet)
module IntSetSet = Set.Make(IntSet)

Answer 2

. .ml , .mli - . .

. - " OCaml".