Actually, the type of "+'a t" is not exported in Map.S, therefore it cannot
be used directly, even when including the module (or I am mistaking the
include semantics).
Le 27 août 2014 16:54, "Yotam Barnoy" <yotambarnoy@gmail.com> a écrit :

> I've recently tried to extend the Map in the standard library with extra
> functionality. This is what I've tried doing:
>
> In a file my_map.ml:
>
> module type S =
>   sig
>     include Map.S
>     val find_lt: key -> 'a t -> 'a
>     val find_gt: key -> 'a t -> 'a
>   end
>
> module Make(Ord: Map.OrderedType) = struct
>   include Map.Make(Ord)
>
>   let find_almost move_f x n =
>     let rec loop lastval n =
>       match n, lastval with
>       | Empty, None   -> raise Not_found
>       | Empty, Some i -> i
>       | Node(l, v, d, r, _) ->
>           let c = Ord.compare x v in
>           let lastval', next = move_f c lastval l d r in
>           loop lastval' next
>   in loop None n
>
>   let move_lt c lastval l d r =
>     if c <= 0 then lastval, l else Some d, r
>
>   let move_gt c lastval l d r =
>     if c < 0  then Some d, l else lastval, r
>
>   let find_gt x n = find_almost move_gt x n
>   let find_lt x n = find_almost move_lt x n
> end
>
> Can anyone tell me why the compiler complained about Empty being an
> unbound constructor when it's declared in Map.Make, which I include?
>
> Thanks
> Yotam
>