[Caml-list] Re: The rec/nonrec debate

[Hongbo Zhang <bobzhang1988@gmail.com>]

On 5/20/13 10:31 AM, Dario Teixeira wrote:
> Hi,
>
Hi,
    I would like to have a self keyword (for the convenience of 
copy-paste and metaprogramming :-))

--------------
    type 'a t = A of 'a self | B of 'a self | C of string

    type 'a t1 = A of 'a self | B of 'a self | C of string | D of int
----
    If we don't like to introduce a new keyword, just replace self with 
an existing keyword , e.g, rec.
>
> As you know, there is in OCaml some asymmetry regarding the rec/nonrec
> defaults for type and value declarations.  Types are recursive by default
> and there's no way to "unrecurse" them, whereas values are by default not
> recursive and can be made recursive via the "rec" keyword.
>
> The unrecursiveness of type declarations is cause for some chagrin, as a
> recent ticket on Mantis demonstrates [1].
>
> Here's something I wonder: if one were to wipe the slate clean, is there
> consensus among the community about the best defaults?  I'm leaning towards
> having nonrec as the default behaviour for *both* types and values, and
> using "rec" as the keyword for recursive types and values.  This scheme
> would obviate the need for an actual "nonrec" keyword.
>
> Obviously, such a change would be too intrusive to make to OCaml.  However,
> since people are working on "Next Generation ML" languages like Mezzo [2],
> I think it would be good to get the community's pulse on this subject.
> (Btw, from the examples posted on Mezzo's homepage, it seems to use the
> same defaults as OCaml).
>
> Your thoughts?
>
> Best regards,
> Dario Teixeira
>
> [1] http://caml.inria.fr/mantis/view.php?id=6016
> [2] http://gallium.inria.fr/~protzenk/mezzo-lang/
>
>