(j3.2006) [ukfortran] (SC22WG5.4170) Urgent: letter ballot on interps

Bill Long longb
Wed Feb 10 13:51:06 EST 2010

N.M. Maclaren wrote:
> On Feb 10 2010, Bill Long wrote:
>> Comment for F03/0039 - HYPOT()
>> Nick's comments about the IEEE nonconformance of the proposed change
>> might be considered for 13.7.69 "HYPOT (X, Y)" in F08
>> 09-007r3[353:18-27].  The HYPOT defined in Note 14.7 is not really
>> claimed to be the official IEEE HYPOT, but rather is a contrivance to
>> illustrate the setting and getting of IEEE flags.
> Ah!  That confused me.
>> would result in a NaN result.  It might also make Fred Tydeman happier
>> if the Note pointed out that the example is not an implementation of
>> the IEEE HYPOT function (at least it's not a valid one).  I believe
>> that Fred (and maybe Nick) would be happy of the name of the function
>> were something other than HYPOT, to avoid confusion with the IEEE
>> HYPOT function.
> It would assuredly be less confusing.

The potential for confusion is  greater in F08.  In the context of the 
F03 standard (against which the interp is formally filed),  one could 
argue that only "experts" who knew about HYPOT from elsewhere would be 
confused.  In F08 we actually have an intrinsic function with this name 
and the same argument list.  The temptation to assume the Note is 
referring to the same function as the one specified in Clause 13 seems 
quite high to me.


> On the F2008 point, I don't approve of IEEE's inconsistent approach to
> NaNs, but this is one of the less problematic cases, and there needs to
> be very strong reason to be incompatible with its explicit wording.
> Regards,
> Nick.

Bill Long                                           longb at cray.com
Fortran Technical Support    &                 voice: 651-605-9024
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