On 2005-07-14, Tim Peters <[EMAIL PROTECTED]> wrote: > Python does go out of its way to raise ZeroDivisionError when > dividing by 0. > >> 1/0 is defined by the standard as +Inf and 0/0 is NaN. >> >> That's what my platform does for programs written in C. > > IOW, that's what your platform C does (the behavior of these > cases is left undefined by the C89 standard, so it's not the > case that you can write a _portable_ C89 program relying on > these outcomes).
True, but as a paracial matter, all of the C platforms I care about all do obey IEEE 754. > What does your platform C return for the integer expression > 42/0? Is any other outcome "wrong"? I guess I though it was obvious from my reference to IEEE 754 that I was referring to floating point operations. I don't know (or generally care) what my C platform does for integer divide by zero. >> Python apparently checks for division by zero and throws and >> exception rather than returning the correct value calculated >> by the underlying platform. >> >> Is there any way to get Python to return the correct results >> for those operations rather than raising an exception? > > No, except when using the decimal module. The latter provides > all the facilities in IBM's proposed standard for decimal > floating-point, which intends to be a superset of IEEE 854: > > http://www2.hursley.ibm.com/decimal/ > > It's relatively easy to do this in the decimal module because > it emulates, in software, all the gimmicks that most modern > FPUs provide in hardware. > > Note that support for 754 was rare on Python platforms at the > time Python was designed, and nobody mentioned 754 support as > even a vague desire in those days. I often foget how old Python is. Still, I've been using IEEE floating point in C programs (and depending on the proper production and handling of infinities and NaNs) for more than 20 years now. I had thought that Python might have caught up. > In the absence of user interest, and in the absence of HW > support for NaNs or infinities on most Python platforms, Really? I would have guessed that most Python platforms are '586 or better IA32 machines running either Windows or Linux. They all have HW support for NaNs and Infinities. > the decision to raise an exception was quite sensible at the > time. Python could not have implemented 754 semantics without > doing emulating fp arithmetic in SW on most platforms (as the > decimal module does today), and for much the same reasons you > can't give a non-silly answer to my earlier "what does your > platform C return for the integer expression 42/0?" question > today <wink>. > >> There's no way to "resume" from the exception and return a >> value from an exception handler, right? > > Correct. > > Note that there's a huge, current, informed discussion of > these issues already in the math.nroot thread. -- Grant Edwards grante Yow! It's OKAY --- I'm an at INTELLECTUAL, too. visi.com -- http://mail.python.org/mailman/listinfo/python-list
