>
> Not sure I got this. Any container may be empty or not empty.
>
I just pointed out that similarity between usage of pointer and an object
directly only holds for pointer-to-array-like objects, not for other
containers.


> Usually you use more than the first element.
>
Right but in that case you don't check just for empty-ness, you check `if
(size() > N)`.

Maybe it's just me but I was never tempted to use conversion to bool for
containers to check their empty-ness and I don't see why more implicit
check in `if (v)` is any better than explicit `if (!v.empty())`.

On Thu, Oct 19, 2023 at 1:57 PM Alex Rozenman <rozenman_at_[hidden]> wrote:

> Not sure I got this. Any container may be empty or not empty.
>
> On Thu, Oct 19, 2023 at 1:47 PM Oleksandr Koval via Std-Proposals <
> std-proposals_at_[hidden]> wrote:
>
>> The code like
>> ```
>> if (vect) foo(vect[0]);
>> ```
>> doesn't make sense for all containers, e.g. for unordered_map so this
>> `operator bool` proposal is not generic.
>>
>> My personal mental model about `operator bool` is a check when an object
>> doesn't exist or it's not usable (in a normal way) or, if it's a wrapper,
>> it wraps nothing.
>>
>> On Thu, Oct 19, 2023 at 1:40 PM Marcin Jaczewski via Std-Proposals <
>> std-proposals_at_[hidden]> wrote:
>>
>>> czw., 19 paź 2023 o 12:27 Bo Persson via Std-Proposals
>>> <std-proposals_at_[hidden]> napisał(a):
>>> >
>>> > On 2023-10-19 at 12:05, Alex Rozenman via Std-Proposals wrote:
>>> > > In many cases, when it is needed to check if a container not empty,
>>> > > "size()" or "empty()" functions are used:
>>> > >
>>> > > if (vect.size() != 0) {
>>> > >
>>> > > // vector is not empty
>>> > >
>>> > > }
>>> > >
>>> > > if (!vect.empty()) {
>>> > >
>>> > > // vector is not empty
>>> > >
>>> > > }
>>> > >
>>> > >
>>> > > It seems that both variants are not expressive enough, so an explicit
>>> > > function may be required, like:
>>> > >
>>> > > if (vect.not_empty()) {
>>> > >
>>> > > // vector is not empty
>>> > >
>>> > > }
>>> > >
>>> >
>>> > Could you live with if(not vect.empty()) ?
>>> >
>>> > If so, that already works.
>>> >
>>> >
>>> >
>>> > >
>>> > > In this message I would like to suggest to use of a bool casting
>>> > > operator as the most clean form of this function:
>>> > >
>>> > > if (vect) {
>>> > >
>>> > > // vector is not empty
>>> > >
>>> > > }
>>> > >
>>> >
>>> > It might be "clean", but I read this as vect is a pointer that might be
>>> > null. Not obvious how this is an improvement.
>>>
>>> ```
>>> if (vect) foo(vect[0]);
>>> if (ptr) foo(ptr[0]);
>>> ```
>>> Both are equivalent.
>>> At least in my code base I use the `bool` operator like this.
>>>
>>> >
>>> >
>>> >
>>> >
>>> > --
>>> > 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
>>>
>>
>>
>> --
>> Regards,
>> Oleksandr Koval.
>> --
>> Std-Proposals mailing list
>> Std-Proposals_at_[hidden]
>> https://lists.isocpp.org/mailman/listinfo.cgi/std-proposals
>>
>
>
> --
> Best regards,
> Alex Rozenman (rozenman_at_[hidden]).
>

-- 
Regards,
Oleksandr Koval.