Given:

struct Point {
    int x;
    int y;
    bool operator==(Point const&) const = default;
};

bool a = Point{1, 2} == Point{1, 2};
bool b = Point{1, 2} == Point{1, 3};
bool c = Point{1, 2} == Point{3, 4};

Do you understand what a, b, and c are?

On Mon, Dec 19, 2022 at 9:06 AM Vladimir Grigoriev <vlad.moscow_at_[hidden]>
wrote:

> I am sorry but I have not yet understood what this statement «Otherwise, V
> is false.» mean.
>
> With best regards
> (Vlad from Moscow)
>
> You can meet me at http://cpp.forum24.ru/ or www.stackoverflow.com or
> http://ru.stackoverflow.com
>
>
>
> Понедельник, 19 декабря 2022, 17:54 +03:00 от Barry Revzin <
> barry.revzin_at_[hidden]>:
>
>
>
> On Mon, Dec 19, 2022 at 8:32 AM Vladimir Grigoriev via Std-Discussion <
> std-discussion_at_[hidden]
> <//e.mail.ru/compose/?mailto=mailto%3astd%2ddiscussion_at_[hidden]>>
> wrote:
>
> There is another unclear phrase in the C++ 20 Standard relative to
> comparison operators.
>
> «3 The return value V of a defaulted == operator function with parameters
> x and y is determined by comparing corresponding elements xi and yi in the
> expanded lists of subobjects for x and y (in increasing index order) until
> the first index i where xi == yi yields a result value which, when
> contextually converted to bool, yields false. If no such index exists, V is
> true. Otherwise, V is false.»
>
>
> It would be helpful if you would point out *where* these phrases exist in
> the C++20 Standard, as it would make it easier for people to answer your
> questions. In this case, this is [class.eq]/3 (
> https://eel.is/c++draft/class.eq#3)
>
>
>
> What does the last statement « Otherwise, V is false.»» mean?
>
>
> Does it mean a case when two expanded lists are unequal or something else?
>
>
> No, the expanded lists have to be equal - we have the same type on both
> sides. There are two separate things going on in this paragraph:
>
>
> 1. What work is done? We compare xi == yi until the first i for which
> xi == yi, contextually convertible to bool, yields false.
> 2. What value is returned? If no such i exists, V (the return value)
> is true. Otherwise, V is false.
>
> Introducing V doesn't seem like it adds anything, if the wording said "If
> no such index exists, the return value is true. Otherwise, the return value
> is false." it'd be more direct.
>
>
>
> In any case a code example of such «otherwise» along with the example of a
> trivial comparison that follows would be useful to make the statement more
> clear.
>
> With best regards
> (Vlad from Moscow)
> You can meet me at http://cpp.forum24.ru/ or www.stackoverflow.com or
> http://ru.stackoverflow.com
>
>
>
> Понедельник, 19 декабря 2022, 14:33 +03:00 от Edward Catmur via
> Std-Discussion <std-discussion_at_[hidden]
> <//e.mail.ru/compose/?mailto=mailto%3astd%2ddiscussion_at_[hidden]>>:
>
>
> On Mon, 19 Dec 2022, 11:31 Vladimir Grigoriev via Std-Discussion, <
> std-discussion_at_[hidden]
> <http://e.mail.ru/compose/?mailto=mailto%3astd%2ddiscussion_at_[hidden]>>
> wrote:
>
> Can anybody translate this phrase from the C++ 20 Standard
>
> «Name lookups in the defaulted definition of a comparison operator
> function are performed from a context equivalent to its function-body.»
>
> to the human language?
>
> How can a context be equivalent to a function body? They are two
> different notions.
>
>
> A context equivalent to the context of the function body.
>
>
>
>
> With best regards
> (Vlad from Moscow)
> You can meet me at http://cpp.forum24.ru/ or www.stackoverflow.com or
> http://ru.stackoverflow.com
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