... [Tom Anderson] > So, is there a way of generating and testing for infinities and NaNs > that's portable across platforms and versions of python?
Not that I know of, and certainly no simple way. > If not, could we perhaps have some constants in the math module for them? See PEP 754 for this. ... >> Read the manual for the precedence rules. -x**y groups as -(x**y). -1.0 >> is the correct answer. If you intended (-x)**y, then you need to insert >> parentheses to force that order. > So i see. Any idea why that precedence order was chosen? It goes against > conventional mathematical notation, as well as established practice in > other languages. Eh? For example, Fortran and Macsyma also give exponentiation higher precedence than unary minus. From my POV, Python's choice here was thoroughly conventional. > Also, would it be a good idea for (-1.0) ** 0.5 to evaluate to 1.0j? It > seems a shame to have complex numbers in the language and then miss this > opportunity to use them! It's generally true in Python that complex numbers are output only if complex numbers are input or you explicitly use a function from the cmath module. For example, >>> import math, cmath >>> math.sqrt(-1) Traceback (most recent call last): File "<stdin>", line 1, in ? ValueError: math domain error >>> cmath.sqrt(-1) 1j The presumption is that a complex result is more likely the result of program error than intent for most applications. The relative handful of programmers who expect complex results can get them easily, though. -- http://mail.python.org/mailman/listinfo/python-list
