On Wed, Feb 20, 2013 at 4:37 PM, Dennis E. Hamilton <orc...@apache.org> wrote: > I earlier quoted the applicable (and only) texts from the Standards > themselves, particularly C++ and also the latest C Standard (2011 and C99 > with all Technical Corrigenda through 2007). > > No matter what is said about pow(0,0) in the C99 Rationale v5.10 Appendix F > of April 2003, there are no such requirements in the Standards, including > those versions that have been adopted since 2003. > > - Dennis > > PS: I mentioned cpow(0,0) because of the mathematical relationship and I was > observing that is consistent with the subset that pow(x,y) supports. > > DETAILS > > The definition of domain error is that an implementation-defined value is > returned *and* errno is set to EDOM. There is also the option of triggering > a floating-point exception. I assume that "capable of representation" > *includes* silent NaN and +infinity but for all I know those return with > non-exception domain errors too. Plauger certainly prepared to encounter > those in his implementation (though he also chose pow(0,0) = 1.0). > > The C 99 Rationale is not an ISO/IEC International Standard, regardless of > the INCITS J11 and SC22 WG14 participation. It is not necessary to even know > about it. In particular, > > "This Rationale discusses some language or library features which > were not adopted into the > Standard. These are usually features which are popular in some C > implementations, so that a > user of those implementations might question why they do not appear in the > Standard." [p.5 preceding section 0.1] The Rationale doesn't address that > question users might have. > > "**[T]his rationale is not part of the Standard**" [bottom of page 5, > their emphasis] > > Then there is Appendix F. I have no idea what it means to have "normative" > in the title. This appears to be an IEC 60559 floating-point profile from > NCEC, with certain exceptions to 60559, although not even that is entirely > clear. pow(+inf,0) = pow(0,0) = 1 are stated as required under Appendix F > (bottom of page 180) Adding pow(NaN,0) = 1 (page 182) by taking power(x,0)=1 > as settled for all x is particularly marvelous. >
In other words, C99, in a normative Annex F, section 9.4.4, for implementations that conform to IEEE 754 floating point, says: "pow(x, ±0) returns 1 for any x, even a NaN." Do you see something different? I'd like to make sure we're seeing the same thing here. -Rob > The developers of C 2011 also didn't seem to be under any compulsion with > regard to the C99 Rationale. > > -----Original Message----- > From: Rob Weir [mailto:robw...@apache.org] > Sent: Wednesday, February 20, 2013 10:14 > To: dev@openoffice.apache.org > Subject: Re: Solving this 0⁰ issue correctly (was Re: Calc behavior: result > of 0 ^ 0) > > [ ... ] I'm reading a requirement for pow(x,0) to > return 1 for all values of x. Are you seeing something else? Are you > seeing anything that says a conforming C/C++ runtime may *return* > something other than 1? > > Btw, the rationale for this choice is described on page 182 of this document: > > http://www.open-std.org/jtc1/sc22/wg14/www/C99RationaleV5.10.pdf > > [ ... ] >
