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

["Török Edwin" <edwin+ml-ocaml@etorok.net>]

On 05/20/2013 05:31 PM, Dario Teixeira wrote:
> 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?

Functions should definitely be non-recursive by default (like in OCaml), to at
least explicitly make you think about the termination/stack usage consequences.

For types I'd prefer non-recursive by default, but only for consistency reasons.

For 'rec' on functions it'd be nice if there was a way to require
tail-recursivity, and have the compiler reject the code if its not actually
tail-recursive or calls non-tail-recursive functions.
But what should be the default? If we apply the same reasoning as for 'rec'
(require explicity action for possibly unsafe structure), then
tail-recursive-required should be default, and you'd need a 'nontail' keyword.
That may be somewhat unpractical though, as most tree-handling code would have
to be full of 'nontail'.

Perhaps a more practical approach would be to have this only at the
documentation level, i.e. Mezzo's equivalent of ocamldoc would show a red 'non
tail recursive' marker in the function's doc to alert users to the
non-tail-recursive functions (and a green tail-recursive marker for others).
In fact this might be a nice improvement to ocamldoc too.

Best regards,
--Edwin