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Date: -- (:)
From: Andre Nathan <andre@d...>
Subject: Re: [Caml-list] Another question about modules
Hi

I've run this:

ocamlc -c a.mli
ocamlc -c b.mli
ocamlopt -c a.ml

The third command gives the error. I thought that the circular
dependency problem was related only to mutually-dependent types on
separate modules, but I guess I was wrong.

Searching the archives, it seems that the solution is to eliminate the
references to B in A by passing a function argument to A.f, as in

  type t = { id: int }
  let f bfun x = print_int x.id; bfun x

and then in b.ml something like

  let f x = print_endline (string_of_int 42)
  let _ = let a = { A.id = 1 } in A.f f a

That appears to solve the issue, although in my actual code it means
adding an extra parameter to many functions, since the call to what was
B.f here is somewhat deep in the call stack, so maybe there is a better
solution.

Thanks,
Andre

On Tue, 2008-07-15 at 20:18 -0400, Ashish Agarwal wrote:
> Firstly, you have a circular dependency. How are you compiling? That
> should be the first error you get.
> 
> 
> On Tue, Jul 15, 2008 at 6:51 PM, Andre Nathan <andre@digirati.com.br>
> wrote:
>         I think this is similar to this simpler problem:
>         
>         a.ml:
>         
>          type t = { id: int }
>          let f x = print_int x.id; B.f x
>         
>         a.mli:
>         
>          type t
>          val f : t -> unit
>         
>         
>         b.ml:
>         
>          let f x = print_int 42
>         
>         b.mli:
>         
>          val f : A.t -> unit
>         
>         
>         Which results in "This expression has type t but is here used
>         with type
>         A.t" in a.ml, even though t and A.t are the same type. Is
>         there a
>         general solution for this kind of situation?
>         
>         Thanks,
>         
>         Andre
>         
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>