On Fri, Mar 7, 2014 at 1:24 PM, Andrew Barnert <abarnert@yahoo.com> wrote:
There is no such thing as copying a binary float exactly into a decimal float. Decimal float values are not a superset of binary float values; in either direction, you have to round. Which is what Python 2.7+ does.
Presuming enough digits of precision, every binary float could be represented precisely in decimal. Decimal is base 10, which factors to 2 and 5, meaning all powers of 1/2 and 1/5 can be precisely represented. Binary floats can only be powers of 1/2.