Thank you for the clarification!
> On 10. Jul 2017, at 23:29, Dave Abrahams via swift-users
> <swift-users@swift.org> wrote:
>
>
> on Sun Jul 09 2017, Martin R <swift-users-AT-swift.org> wrote:
>
>> The Comparable protocol requires that < and == impose a strict total
>> order: exactly one of a==b, a<b, a>b must hold for all values a and b
>> of a conforming type.
>>
>> But it is also noted that a conforming type may contain a subset of
>> „exceptional values“ which do not take part in the strict total order
>> (such as FloatingPoint.nan).
>>
>> What does that mean for functions taking comparable arguments, e.g.
>>
>> func mySuperSort<T: Comparable>(a: inout [T]) { }
>>
>> Can the function implementation assume that all values passed to it
>> take part in the strict total order? In other words: „exceptional
>> values“ must not be passed to the function?
>
> Yes
>
>> Or must the function take that case into account and must not assume
>> that exactly one of a==b, a<b,
>> a>b holds for any arguments passed to it?
>
> It need not, but it may do so as a matter of QOI (Quality Of
> Implementation). It is a good idea to make such a function work for NaN
> if you can figure out what the semantics should be and it doesn't overly
> impact the performance of other important use cases.
>
> Hope this helps,
>
> --
> -Dave
>
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