On Thu, 4 May 2023 at 15:35, Thiago Macieira via Std-Proposals <std-proposals@lists.isocpp.org> wrote:

On Thursday, 4 May 2023 01:52:48 PDT David Brown via Std-Proposals wrote:
> You can also do "!!x ^ !!y", using the "convert to bool operator" !!.
> Alternatively, "!x ^ !y" saves two keypresses :-)

This can also be spelt:

!x != !y

Right, I already pointed that out in https://lists.isocpp.org/std-proposals/2023/05/6533.php which is what David was replying to.