On Feb 25, 11:20 am, "John Machin" <[EMAIL PROTECTED]> wrote: [...] > I'm a little puzzled: > > You don't seem to want a function that will tell you the actual number > of significant decimal digits in a particular number e.g. > > nsig(12300.0) -> 3 > nsig(0.00123400) -> 4 > etc > > You appear to be trying to determine what is the maximum number of > significant decimal digits afforded by the platform's implementation > of Python's float type.
Yes you are correct. > Is Python implemented on a platform that > *doesn't* use IEEE 754 64-bit FP as the in-memory format for floats? I had no knowledge of IEEE 754 64-bit FP. The python doc says that floats are implemented using the C 'double' data type but I didn't realise there was a standard for this accross platforms . Thanks for clarifying this. As my question shows I am not versed in floating point arithmetic! Looking at the definition of IEEE 754, the mantissa is made of 53 significant binary digits, which means 53*log10(2) = 15.954589770191003 significant decimal digits (I got 16 with my previous dodgy calculation). Does it mean it is safe to assume that this would hold on any platform? -- Arnaud -- http://mail.python.org/mailman/listinfo/python-list
