Related: https://wg21.link/p2561 error propagation operator

On Thu, 20 Oct 2022 at 08:33, Sebastian Wittmeier via Std-Proposals <
std-proposals_at_[hidden]> wrote:

> Hi Stephane,
>
>
>
> the ternary operator ? has the current disadvantage that it cannot be
> customized.
>
> Customization of ?-> could be useful for smart pointers and iterators,
> when the test should do more than test for false the pointer converted into
> bool.
>
>
>
> Even if a 3-argument operator? or operator?-> would be introduced, with
> current function call semantics, all parameters are evaluated before the
> function call, which would nullify the check for nullptr.
>
>
>
> Similarly && and || cannot be customized fully.
>
>
>
> Perhaps there are ideas for partial evaluations of function parameters in
> general (e.g. "lambda parameters", which can be evaluated in a delayed
> manner by the called function (internally implementable as callback) or
> some fixed ways for certain operators like operator?, operator??,
> operator||, operator?->.
>
>
>
> Sebastian
>
>
> -----Ursprüngliche Nachricht-----
> *Von:* Stéphane Duguay via Std-Proposals <std-proposals_at_[hidden]>
> *Gesendet:* Do 20.10.2022 05:07
> *Betreff:* [std-proposals] The null-aware arrow operator: ?->
> *An:* std-proposals_at_[hidden];
> *CC:* Stéphane Duguay <s_at_[hidden]>;
> The null-aware arrow operator: ?->
>
> Instead of:
> if(ptr)
> ptr->func();
> Write:
> ptr?->func();
>
> The very bad:
> if( ptr && ptr->getSub() )
> ptr->getSub()->func();
> Becomes:
> ptr?->getSub()?->func();
>
> Support for the "default value if ptr is null" use case:
> n = ptr?->get_value() : 42;
> Instead of:
> n = ptr ? ptr->get_value() : 42;
>
> The three-way comparison operator <=> is 3 chars long; ?-> now seems
> reasonable IMHO.
>
> I'm unsure of all the possibilities for null-aware operators in C++,
> but there's probably more to explore. I couldn't find anything in
> relation to "null-aware" on the mailing list archive. "Null safety"
> itself is a wider concept than null-awareness. If this was already
> posted, sorry!
>
> -------
> s|d
> --
> Std-Proposals mailing list
> Std-Proposals_at_[hidden]
> https://lists.isocpp.org/mailman/listinfo.cgi/std-proposals
>
> --
> Std-Proposals mailing list
> Std-Proposals_at_[hidden]
> https://lists.isocpp.org/mailman/listinfo.cgi/std-proposals
>