On 2005-03-09 12:45:57 +0100, Duncan Sands wrote: > The problem is x^0.0 (real exponent), not x^0 (integer exponent).
Well, mathematically, you can distinguish these two functions: powrr: RxR -> R (not defined on (0,0) in particular) and powrz: RxZ -> R (where powint(0,0) = 1) and even other two functions, where R is replaced by C (the complex numbers). Unfortunately, the C language doesn't distinguish them. > Now in practice I can imagine that a language confuses x^integer and > x^real by mapping them to the same function, or only provides a > function for doing x^real. Perhaps this is the case with C? Yes, and to compute complex^integer, you need to use cpow(), AFAIK. I think this is the reason why cpow((0,0),(0,0)) should return 1, just like pow(0,0). > If so, then having 0^0.0 return 1.0 is a convenient hack to work > around that mistake. On the other hand, ignoring such things as > language standards and the weight of history, if there are separate > functions for x^integer and x^real, then in my opinion the most > sensible thing would be for 0^0 to return 1, and 0^0.0 to return > NaN. This might confuse programmers though. They would be two different mathematical functions, thus returning different results should be OK. Anyway the C language has only one function for that (I don't know about the other languages, though). Moreover, the implicit conversions between signed and unsigned integers in C are much more confusing. -- Vincent Lefèvre <[EMAIL PROTECTED]> - Web: <http://www.vinc17.org/> 100% accessible validated (X)HTML - Blog: <http://www.vinc17.org/blog/> Work: CR INRIA - computer arithmetic / SPACES project at LORIA
