Guarding arithmetic

[Laszlo Nagy]

> That can work ONLY if the division of 1/0 doesn't raise an exception.
> This is why the concept of NaN exists; I'm not sure if there's a way
> to tell Python to return NaN instead of bombing, but it's most likely
> only possible with floating point, not integer.
For integers, Python will always raise an exception when you try to 
divide by zero. And integers has nothing to do with NaN. Because NaN is 
meaningful for floating point numbers only. Python can be compiled to 
raise floating point exceptions. (On Python 2, this is a compile time 
option: FPECTL. On Python 3, this can be configured runtime:  
http://docs.python.org/library/fpectl.html )