On Mon, 2023-09-25 at 11:08 +0200, David Brown via Std-Proposals wrote:
> On 23/09/2023 20:35, Arthur O'Dwyer via Std-Proposals wrote:
> > On Sat, Sep 23, 2023 at 2:13 PM Chris Gary via Std-Proposals
> > <
> > std-proposals_at_[hidden] <mailto:std-proposals_at_[hidden]
> > g>>
> > wrote:
> >
> >
> > *move and forward can be defined without compiler hooks. This
> > is
> > where the language does not make architectural assumptions.*
> > *typeid() cannot.*
> >
> >
> > Right.
> >
> > In general: Architecture is disrupted when an unwanted or
> > incompatible role is introduced or required by a dependency.
> > All C++
> > applications are now dependent on the standard library [...] It
> > must
> > be possible to effectively use the language without the
> > library.
> >
> >
> > I agree with you, as a general rule. But, as everyone's saying,
> > you're
> > re-litigating a decision that was already made in
> > - C++20, with the type of `auto x = (1 <=> 2)` being
> > std::strong_ordering and the type of `auto x = (1. <=> 2)` being
> > std::partial_ordering;
> > and that decision was merely in line with the decisions C++ made in
> > - C++20, with basically everything in coroutines;
> > - C++17, with structured bindings' being dependent on
> > std::tuple_size
> > and std::tuple_element <https://eel.is/c++draft/dcl.struct.bind#4>;
> > - C++11, with ranged-for-loops' being dependent on
> > <https://eel.is/c++draft/stmt.ranged#1.3> the magic identifiers
> > "begin"
> > and "end", and the type of `auto x = {1,2}` being
> > std::initializer_list<int>;
> > - C++98, with the type of `auto x = typeid(int)` being
> > std::type_info.
> >
> > You can't invoke a general principle to undo a specific
> > three-years-out-the-door decision, especially when that decision is
> > in
> > line with two-decade-old decisions.
> >
>
> It is /way/ older than that - preceding C++ itself, and preceding
> standardised C. K&R C had the "sizeof" operator return the type
> "size_t", defined in <stdlib.h> and <stddef.h>. So having language
> features rely on definitions from standard library headers is a 50
> year
> old tradition, not merely two decades old!
>
>

One major difference compared to `<=>` is that `sizeof` can be used
without including `<stddef.h>`.

I see some merit in not requiring includes for language constructs like
`1 <=> 2` or `{1, 2}`, similarly how it's not needed for `sizeof`.

Cheers,
Lénárd