[Numpy-discussion] Random int64 and float64 numbers

[David Warde-Farley]

On 5-Nov-09, at 4:54 PM, David Goldsmith wrote:

> Interesting thread, which leaves me wondering two things: is it  
> documented
> somewhere (e.g., at the IEEE site) precisely how many *decimal*  
> mantissae
> are representable using the 64-bit IEEE standard for float  
> representation
> (if that makes sense);

IEEE-754 says nothing about decimal representations aside from how to  
round when converting to and from strings. You have to provide/accept  
*at least* 9 decimal digits in the significand for single-precision  
and 17 for double-precision (section 5.6). AFAIK implementations will  
vary in how they handle cases where a binary significand would yield  
more digits than that.

David