On 24/10/2024 20.03, Paul Caprioli via Std-Proposals wrote:
> My colleagues and I are looking into the accuracy of complex mathematical operations/functions with different compilers/libraries.
> The first version of our paper is available at: https://inria.hal.science/hal-04714173
>
> In the Numerics [complex.transcendentals] section of the C++ standard, some functions (e.g., acos) have a remark, "Behaves the same as the C function cacos.
> See also: ISO/IEC 9899:2018." Others (e.g., log) have a note, "The semantics of this function are intended to be the same in C++ as they are for clog in C."
> Others (e.g., cos) have neither.
>
> Are these differences intentional and meaningful? I would appreciate any pointers or help in learning more.

These words probably haven't been touched for three decades.

My guess is that we want "the same" behavior as in C for all of those functions
(e.g. regarding branch cuts), and the differences in note phrasing are accidental.

I would guess that all C++ implementations defer to the corresponding C functions
for those trigonometrics.


Quote from the paper, section 3:

"The following table shows the results for the complex bivariate operations in single precision."

What are the "results"? It would be good to repeat what the numbers mean.

Jens