On Mon, Sep 20, 2010 at 3:= 02 PM, Dumitru Potop-Butucaru <dumitru.potop_butucaru@inria.fr> = wrote:

Yes, but this involves duplicating code, and I really hate to duplicate cod= e, even in interfaces.

To also answer Ashish: I want to define an interface to modules where I use= a very specific kind of map. Of course, I could leave Map.Make polymorphic= , but that is a different module type than the one I want to use to represe= nt my theory.

Yours,
Jacky

On 20/09/2010 19:58, Martin Jambon wrote:

Dumitru Potop-Butucaru wrote:

Actually, I was looking for a way to specialize a whole module,
not just the associated type (**this** I knew how to do).
I would like to write something like:

=A0 =A0 include module type of Set.Make(String) with 'a=3D int

Is this possible?

I don't know about such a shortcut, but the following works and the int= erface
is easier to use for a human:

(* foo.mli *)
type key =3D string
type value =3D string
type map
val empty : map
val is_empty : map -> =A0bool
val add : key -> =A0value -> =A0map -> =A0map
val find : key -> =A0map -> =A0value
val remove : key -> =A0map -> =A0map
val mem : key -> =A0map -> =A0bool
val iter : (key -> =A0value -> =A0unit) -> =A0map -> =A0unit val map : (value -> =A0value) -> =A0map -> =A0map
val mapi : (key -> =A0value -> =A0value) -> =A0map -> =A0map val fold : (key -> =A0value -> =A0'a -> =A0'a) -> =A0ma= p -> =A0'a -> =A0'a
val compare : (value -> =A0value -> =A0int) -> =A0map -> =A0map= -> =A0int
val equal : (value -> =A0value -> =A0bool) -> =A0map -> =A0map = -> =A0bool

(* foo.ml *)
module M =3D Map.Make (String)
include M
type value =3D string
type map =3D string M.t

Martin

Yours,
Jacky Potop

On 20/09/2010 16:57, Ashish Agarwal wrote:

module M =3D Map.Make(String)

type t =3D int M.t

Type t is the type of maps from string's to int's. Or alternatively=
write a
function that assumes 'a is some specific type:

# let f m =3D M.fold (fun _ x y -> =A0 x + y) m 0;;
val f : int M.t -> =A0 int =3D<fun>

On Mon, Sep 20, 2010 at 10:35 AM, Dumitru Potop-Butucaru<
dumitr= u.potop_butucaru@inria.fr> =A0 wrote:

Hello,

I'm certain most users here will consider the question trivially simple= ,
but I browsed the documentation without finding a solution.

The question is quite general: Given a polymorphic definition like
Map.Make(X), where
X is some module, how can I specialize its 'a type parameter, e.g. by setting it to Y, so that
I have maps from X to Y ?

Yours,
Jacky Potop

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