Grant Edwards wrote: > You must have gone to a different school than I did. I learned > that for IEEE floating point operations a/0. is INF with the > same sign as a (except when a==0, then you get a NaN).
I'm not talking about CS and IEEE floating point ops. I was referring to plain good old math. Python targets both newbies and professionals. That's the reason for two math modules (math and cmath). > That's certainly what I expected after being told that Python > doesn't do anything special with floating point operations and > leaves it all up to the underlying hardware. Quoting from the > page to linked to, it's also what the IEEE standard specifies: > > The IEEE floating-point standard, supported by almost all > modern processors, specifies that every floating point > arithmetic operation, including division by zero, has a > well-defined result. In IEEE 754 arithmetic, a/0 is positive > infinity when a is positive, negative infinity when a is > negative, and NaN (not a number) when a = 0. > > I was caught completely off guard when I discovered that Python > goes out of its way to violate that standard, and it resulted > in my program not working correctly. Python's a/0 outcome doesn't violate the standards because Python doesn't promise to follow the IEEE 754 standard in the first place. Mark and I are working hard to make math in Python more reliable across platforms. So far we have fixed a lot of problems but we haven't discussed the a/0 matter. The best we could give you is an option that makes Python's floats more IEEE 754 like: >>> from somemodule import ieee754 >>> with ieee754: ... r = a/0 ... print r inf Christian -- http://mail.python.org/mailman/listinfo/python-list
