>however I don't think you should be able to compare these directly.
>is like comparing unsigned with float point or bool with int.

Why? Because the allocator is part of the type? Well, is there a good
reason for it to be part of the type? why not type erase it like the
std::shared_ptr Deleter and Allocator

On Sun, Sep 13, 2020 at 5:06 PM Nikolay Mihaylov via Std-Proposals <
std-proposals_at_[hidden]> wrote:

> Here some examples:
>
> https://godbolt.org/z/reeTY5
>
> including:
>
> template<class T1, class A1, class T2, class A2>
> bool operator==(const std::basic_string<char, T1, A1> &a, const
> std::basic_string<char, T2, A2> &b){
> return strcmp(a.c_str(), b.c_str()) == 0;
> }
>
> however I don't think you should be able to compare these directly.
> is like comparing unsigned with float point or bool with int.
>
> Nikolay
>
> On Sun, Sep 13, 2020 at 4:47 PM Arthur O'Dwyer via Std-Proposals <
> std-proposals_at_[hidden]> wrote:
>
>> On Sun, Sep 13, 2020 at 8:17 AM Robert Behar via Std-Proposals <
>> std-proposals_at_[hidden]> wrote:
>>
>>> currently I can't compare two strings with differing allocators.
>>>
>>
>> IIUC, you're complaining that
>> https://godbolt.org/z/db9MWW
>>
>> std::string a;
>> std::pmr::string b;
>> return a == b;
>>
>> does not compile, whereas
>>
>> return a == std::string_view(b);
>>
>> does compile.
>>
>> Marshall Clow's P0805 "Comparing Containers" would have fixed this
>> incidentally for std::vector == std::pmr::vector, as part of its larger
>> motivation of fixing vector<int> == vector<long>.
>> http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p0805r2.html
>>
>> But P0805 specifically says:
>> > I have not suggested changes to basic_string, because it does not use
>> lexicographical_compare, but delegates to a traits class.
>>
>> Also, P0805 seems to be motionless? The last update was in 2018, and it
>> didn't go into C++20.
>> From the private Committee notes, it appears to me that it collided
>> head-on with C++20 Ranges' notion of "constrained algorithms," where you're
>> not supposed to ever be able to compare T and U unless they have a
>> common_reference type, which is not true for e.g. `int` and `long`.
>>
>> So it might be useful to provide a very limited fork of P0805 that
>> - only permits different allocators, not different element types
>> - includes basic_string as well as all the STL containers
>>
>> my $.02,
>> –Arthur
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