Use of C99 extra long double math functions after r236148

[Stephen Montgomery-Smith]

On 07/18/2012 05:42 PM, Peter Jeremy wrote:
> On 2012-Jul-18 10:07:41 -0500, Stephen Montgomery-Smith <stephen at missouri.edu> wrote:
>> I went on a long road trip yesterday, so I didn't get any code written,
>> but I did have a lot of thoughts about clog and casinh.
>
> Can I suggest you have a read through "Implementing the Complex
> Arcsine and Arccosine Functions Using Exception Handling" by
> T. E. Hull Thomas F. Fairgrieve and Ping Tak Peter Tang, ACM
> Transactions on Mathematical Software, Vol. 23, No. 3, September 1997.
> Based on a quick skim, it includes fairly detailed pseudocode,
> together with an error analysis.

OK, I will do that.

My pseudo code is different in that I use clog, and they do not.  I'll 
probably go with my approach, but use lots of ideas from this paper as 
seems appropriate.  I might even try both approaches and see which seems 
to be the winner,

>
> On 2012-Jul-18 16:09:06 -0500, Stephen Montgomery-Smith <stephen at missouri.edu> wrote:
>> Am I to understand that the inexact flag should be set anytime a
>> floating point operation produces an answer that is not guaranteed
>> exact?
>
> My understanding is, yes.  For the transcendental functions, that
> means the inexact flag should almost always be raised and the problem
> becomes when not to raise it.  Eg sin(0) == 0 and presumably doesn't
> set the inexact flag.
>
>>   For example, should 1.0/3.0 and sqrt(2.0) raise the inexact flag?
>
> Yes and yes.  I notice our sqrtl() actually tests the inexact flag of
> an intermediate calculation to determine the correct rounding for the
> result.

Thank you for the clarification.  I will definitely set the inexact flag 
under the circumstances pointed out by Steve.  Otherwise, I will rely on 
clog and csqrt to set the inexact flag.  (And clog will depend upon log, 
hypot and atan2 to set the inexact flag.)