Re: [Ocaml-lib-devel] some proposals

[Nicolas C. <war...@fr...>]

> Which means we're probably stuck with something like:
>
> let Int.compare x y = if (x < y) then -1 else if (x > y) then 1 else 0

Uh !
This time Brian you're using up to TWO times polymorphic comparison !
I think the most easy solution is really to use the substraction, but that
will cause the problems you showed with max_int / min_int , and doing some
previous boundary tests before return x - y will increase the cost of it. So
my conclusion is this is an user-specific problem (some might need max_int
while some might not ) which should be addressed by not adding the module
Int to the ExtLib, although it was a good idea.

About the partial_map, this can be done using a fold_left, which is more
appropriate since you don't allocate None/Some blocks . But I think perhaps
fold_left/right are not so easy to use in the first place, so maybe having a
partial_map would be nice , but I would rename it to filter_map since this
can be done using one map + one filter.

BTW, I would prefer a more simple version of the Brian one, which does not
need two loops :

let filter_map f l =
    let rec loop dst = function
        | [] -> ()
        | h :: t ->
            match f t with
            | None -> loop dst t
            | Some x ->
                    let r = [ x ] in
                    Obj.set_field (Obj.repr dst) 1 (Obj.repr r);
                    loop r t
    in
    let dummy = [ Obj.magic () ] in
    loop dummy l;
    List.tl dummy

Nicolas Cannasse