using functors in objects

using functors in objects

[Jacques Le Normand]

[-- Attachment #1: Type: text/plain, Size: 333 bytes --]

hello caml-list,
I would like to do something like this:

module A (X: sig type t end) =
struct
  class c =
  object
    val b = (None : X.t option)
  end
end

class d =
module Y = A(struct type t = d end)
object
  inherit Y.c
end

which, of course, gives me a syntax error. is it possible to bind a module
inside a class?
--Jacques

[-- Attachment #2: Type: text/html, Size: 433 bytes --]

Re: [Caml-list] using functors in objects

[Andrej Bauer]

Perhaps something like this with recursive modules. I have a feeling it
can be simplified, though.

Andrej

--------------------
module A (X: sig type t end) =
struct
  class c =
  object
    val b = (None : X.t option)
  end
end

module rec D : sig
  class d : object val b : D.d option end
end =
struct
  class d =
  object
    inherit Y.c
  end
end

and Y :
sig
  class c : object val b : D.d option end
end =
  A(struct type t = D.d end)

class d = D.d

----------------

Re: [Caml-list] using functors in objects

[Julien Signoles]

> Perhaps something like this with recursive modules. I have a feeling it
> can be simplified, though.
>
> Andrej
>
> --------------------
> module A (X: sig type t end) =
> struct
>  class c =
>  object
>    val b = (None : X.t option)
>  end
> end
>
> module rec D : sig
>  class d : object val b : D.d option end
> end =
> struct
>  class d =
>  object
>    inherit Y.c
>  end
> end
>
> and Y :
> sig
>  class c : object val b : D.d option end
> end =
>  A(struct type t = D.d end)
>
> class d = D.d
>
> ----------------

it doesn't work because the recursive modules cannot be safely 
initialized in such a case:

$ ocamlc -v
The Objective Caml compiler, version 3.10.1
Standard library directory: /home/jsignole/local/godi/lib/ocaml/std-lib
$ ocamlc -o modclass modclass.ml
$ ./modclass
Fatal error: exception Undefined_recursive_module("modclass.ml", 23, 2)

Yet I haven't a good solution for such a think :-(.

--
Julien

Re: [Caml-list] using functors in objects

[Andrej Bauer]

Julien Signoles wrote:
> $ ocamlc -v
> The Objective Caml compiler, version 3.10.1
> Standard library directory: /home/jsignole/local/godi/lib/ocaml/std-lib
> $ ocamlc -o modclass modclass.ml
> $ ./modclass
> Fatal error: exception Undefined_recursive_module("modclass.ml", 23, 2)

Oh my god! What ever happened to safety?! You know, the little theorem
that says "If a program is well typed then it does not explode in your
face".

I naively thought it would work because it compiled. Yuck!

Andrej