[Cfp-interest 3090] Re: csinh(x + i y) - G.6.3.5 - 5th bullet point of special cases

[Damian McGuckin]

On Sun, 7 Apr 2024, Jim Thomas wrote:

> Conjugate, odd, and even were used where it seemed the extra bullets 
> required to do otherwise would expand the specification unduly. Using 
> them was not an absolute principle. For example, a better grouping of 
> the bullets might have seemed more important. There might be 
> inconsistencies here that would be important to remove, but we need to 
> ask whether a considered change would lead to an overall significantly 
> clearer specification?

As an example

 	csinh(x + i INF) returns NaN + i NaN for positive finite x

And because it is odd

 	csinh(-x + i INF) returns NaN + i NaN

But this could be written as

 	csinh(x + i INF) returns NaN + i NaN for finite non-zero x

Interesting, this is exactly what happens in ctanh

 	ctanh(x + i INF) returns NaN + i NaN for finite non-zero x

It could be written the same was as csinh (but it is not).

I chose to write 'csinh' the same way as ctanh() for consistency.

That also is the same as ccosh() (but then ccosh() is even).

Rather than looking at the various functions, I have instead taken a view 
to look at each special case argument across all the functions and made 
them as consistent as I can.

- Damian