Re: [Ocaml-lib-devel] Enum documentation and bug fix

[Brian H. <bri...@ql...>]

On Fri, 20 Jun 2003, Nicolas Cannasse wrote:

> I added the complete documention to Enum. (comments are welcome )
> While reading the documentation specification, I found a bug.
> Actually the iter2 , fold2 and others were not correct because of the
> following
> 
> f (t.next()) (u.next())
> 
> if t.next() was called and then u.next() was raising No_more_elements , we
> were loosing an element of t.
> I modified the implementation of theses so now the element is saved and
> pushed back (using the new "push" function) if needed.
> But as for map2 (and map2i) this would involve setting up a try .. catch
> block for every call to next , which has already been tagged as
> not-so-efficient , I have then temporay removed theses two.

This is one place where has_next would be usefull.  It would allow us to 
implement iter2 like:

let iter2 f t u =
    let rec loop () =
        if (t.has_next()) && (u.has_next()) then
            begin
                f (t.next()) (u.next());
                loop ()
            end
        else
            ()
    in
    loop ()

Brian