Vsevolod Fedorov wrote:
> Hello!
>
> I want to define two records referencing each other. First record (A)
> has direct reference to second (B) and second (B) has weak hash table to
> list records A, which have reference to it. For example (pseudo code):
>
> type a
> {
> id : int ;
> mutable field1 : string;
> mutable b : B;
> }
> type b
> {
> id : int;
> mutable field2 : string;
> a_list : Weak-Hashtbl(a); (* they referenced me *)
> }
>
> Is it possible at all?
> Is it possible with A and B declarations in separate files?
>
> Any hints and references are welcomed.
Assuming your weak hash table module is created by a functor parametrized by
type "a", the problem is solved with recursive modules. They are documented as
a language extension in the reference manual:
http://caml.inria.fr/pub/docs/manual-ocaml/manual021.html#toc75
Here is some code that compiles and runs without raising the
Undefined_recursive_module exception:
module rec W : Weak.S =
Weak.Make (
struct
type t = X.a
let equal = ( = )
let hash = Hashtbl.hash
end
)
and X :
sig
type a = {
id : int ;
mutable field1 : string;
mutable b : b;
}
and b = {
id : int;
mutable field2 : string;
a_list : W.t; (* they referenced me *)
}
end =
struct
type a = {
id : int ;
mutable field1 : string;
mutable b : b;
}
and b = {
id : int;
mutable field2 : string;
a_list : W.t; (* they referenced me *)
}
end
Martin
--
http://mjambon.com/
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