On Tuesday, October 23, 2018 at 10:57:59 AM UTC+11, Botond Ballo wrote:
> On Mon, Oct 22, 2018 at 7:47 PM, <gsqu...@mozilla.com> wrote:
> > Here's one I'd like:
> > for (int i = ...; test(i); i = next(i)) {
> > if (good_stuff(i)) { break; /* goto past `else` block */ }
> > } else {
> > /* test(i) failed, i.e., we didn't `break` */
> > do_something(i); // decls inside `for(...)` still in scope.
> > }
> > and/or:
> > for (auto& x: xs) {
> > if (good_stuff(x)) { break; /* goto past `else` block */ }
> > } else {
> > /* went off-range, i.e., we didn't `break` */
> > }
>
> This has actually been proposed before! Here's the latest iteration of
> the proposal (dated February 2017):
>
> http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2017/p0082r2.pdf
>
> and here's my summary of its discussion, from my blog post about the
> meeting where it was discussed [1]:
>
> "An updated version of for loop exit strategies, which proposes to
> allow adding blocks of code at the end of a for loop that run when the
> loop exits by breaking (introduced by the keyword on_break), and when
> the loop runs to completion (introduced by on_complete). The only
> thing that has changed since the last revision of this proposal is the
> keywords – they were catch break and catch default in the previous
> version. EWG didn’t love the new keywords, either, and was generally
> lukewarm towards the proposal in terms of motivation, so it’s not
> clear if this is going anywhere."
>
> Given that this has already been proposed and effectively shot down, I
> think it makes to try and re-propose it only if we have new
> information to bring to the table, e.g. compelling new motivation or a
> design alternative that hasn't been considered.
>
> Cheers,
> Botond
>
>
> [1]
> https://botondballo.wordpress.com/2017/03/27/trip-report-c-standards-meeting-in-kona-february-2017/
Thanks for the info.
I guess it's quite a common need, it must have been on many minds since 1972.
:-)
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