Sorry Chris, you just happened to step on a landmine of 10+ years of
discussion without reading the prior art:) spaceship was really difficult
to design, and bringing that up again brings all of the "oh, another person
that thinks the same thing everyone thinks in the first place and its then
educated, here we go again" up for people.

On Mon, Sep 25, 2023, 07:15 Chris Gary via Std-Proposals <
std-proposals_at_[hidden]> wrote:

> So what's the problem with the current implementation?
>>
>
> #include <compare> // <-- has a bigger maintenance footprint than it
> seems. Did I use a library feature? No, I just wanted to use <=>...
>
> That's really it for now.
> The rest is just "let me use my own int-alike" and why that is possible.
>
> I'm getting responses as though I've somehow gone home-to-home and kicked
> their pets.
>
> When you present an idea in a forum and the first thing you get from a a
> few people who, for all intents and purposes, you should expect to behave
> in a professional manner spit out one "go foad" after another its hard to
> gauge the community temperament.
>
> On Sun, Sep 24, 2023 at 4:03 PM Thiago Macieira via Std-Proposals <
> std-proposals_at_[hidden]> wrote:
>
>> On Sunday, 24 September 2023 13:57:38 PDT Chris Gary via Std-Proposals
>> wrote:
>> > enum class Relation : int
>> > {
>> > Undefined = -2,
>> > Less = -1,
>> > Equal = 0,
>> > Greater = 1
>> > };
>> >
>> > inline constexpr Relation ClampToValid( Relation r ) noexcept
>> > {
>> > const auto u = (int)r + 1;
>> > const auto v = 2 - u;
>> > const auto w = u | ((u|v) >> (bitCount<int>-1));
>> > return (Relation)( w - 1 );
>> > }
>> >
>> > // Relational operators that take "Relation" etc...
>> > `
>> > Now, if <=> could just return `int` or anything that can round-trip to
>> an
>> > `int` implicitly, *and* enum classes could expose implicit conversions,
>> > this could all be safely encapsulated without creating incorrect code
>> that
>> > tries to compare a `Relation` value and not getting the magic
>> `undefined`
>> > result - everything would get mapped into to the set {-2,-1,0,1} before
>> > comparison. The "sign of difference" rule still applies everywhere, and
>> > comparisons are allowed to return any other random value to mean
>> > "undefined". In cases where the meaning of the return value means more
>> than
>> > just "undefined", and the code still assumes the semantics of
>> "Relation",
>> > it wasn't written to deal with the failure anyway (generally, just
>> capture
>> > the original int and propagate an error/throw an exception).
>>
>> I'm missing something.
>>
>> How is this any different to std::strong_ordering?
>>
>> The implementations do use values -1, 0, 1 and something else (2, -2,
>> -127,
>> etc.). They just happen to wrap them in a class that can relate to
>> partial_ordering, weak_ordering.
>>
>> So what's the problem with the current implementation?
>>
>> --
>> Thiago Macieira - thiago (AT) macieira.info - thiago (AT) kde.org
>> Software Architect - Intel DCAI Cloud Engineering
>>
>>
>>
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>>
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