[Caml-list] using arguments insides functors

[Caml-list] using arguments insides functors

[nakata keiko]

Hello,
why the following code does not get type checked ?

module type I = 
  sig 
    module type T
  end


module F = functor (Elt : I) ->
  struct
    module type T = Elt.T
    module F = functor (Elt : T) -> 
      struct 
	include Elt
      end
  end

Thanks,
Keiko

-------------------
To unsubscribe, mail caml-list-request@inria.fr Archives: http://caml.inria.fr
Bug reports: http://caml.inria.fr/bin/caml-bugs FAQ: http://caml.inria.fr/FAQ/
Beginner's list: http://groups.yahoo.com/group/ocaml_beginners

Re: [Caml-list] using arguments insides functors

[Andreas Rossberg]

nakata keiko wrote:
> why the following code does not get type checked ?
> 
> module type I = 
>   sig 
>     module type T
>   end
> 
> module F = functor (Elt : I) ->
>   struct
>     module type T = Elt.T
>     module F = functor (Elt : T) -> 
>       struct 
> 	include Elt
>       end
>   end

Because "include" only applies to modules that are structures, since it 
is meant to copy its fields to the current scope. In your example 
however, Elt has some abstract module type T, so it does not meet that 
requirement. What should the include mean if you applied the outer F like

   F (struct module type T = functor (X : sig end) -> sig end end)

? And how could you express the result type of F without knowing the 
structure of Elt?

Cheers,

	- Andreas

-- 
Andreas Rossberg, rossberg@ps.uni-sb.de

Let's get rid of those possible thingies!  -- TB

-------------------
To unsubscribe, mail caml-list-request@inria.fr Archives: http://caml.inria.fr
Bug reports: http://caml.inria.fr/bin/caml-bugs FAQ: http://caml.inria.fr/FAQ/
Beginner's list: http://groups.yahoo.com/group/ocaml_beginners

Re: [Caml-list] using arguments insides functors

[nakata keiko]

> Because "include" only applies to modules that are structures, since it 
> is meant to copy its fields to the current scope. In your example 
> however, Elt has some abstract module type T, so it does not meet that 
> requirement. What should the include mean if you applied the outer F like
> 
>    F (struct module type T = functor (X : sig end) -> sig end end)
> 
> ? And how could you express the result type of F without knowing the 
> structure of Elt?
> 
> Cheers,
> 
> 	- Andreas
> 
Mm-hm, I see.
Thank you.

Keiko

-------------------
To unsubscribe, mail caml-list-request@inria.fr Archives: http://caml.inria.fr
Bug reports: http://caml.inria.fr/bin/caml-bugs FAQ: http://caml.inria.fr/FAQ/
Beginner's list: http://groups.yahoo.com/group/ocaml_beginners