Mark Dickinson wrote: > On Thu, Mar 25, 2010 at 2:08 PM, Nick Coghlan <ncoghlan at gmail.com> wrote: >> Jesus Cea wrote: >>> But IEEE 754 was created by pretty clever guys and sure they had a >>> reason for define things in the way they are. Probably we are missing >>> something. >> Yes, this is where their "implementable in a hardware circuit" focus >> comes in. They were primarily thinking of a floating point >> representation where the 32/64 bits are *it* - you can't have "multiple >> NaNs" because you don't have the bits available to describe them. > > I'm not so sure about this: standard 64-bit binary IEEE 754 doubles > allow for 2**53-2 different nans (2**52-2 signaling nans, 2**52 quiet > nans): anything with bit pattern (msb to lsb) > > x1111111 1111xxxx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx > > is an infinity or a nan, and there are only 2 infinities. I stand corrected :) It still seems to me that the problems mostly arise when we're trying to get floats and Decimals to behave like Python *objects* (i.e. with reflexive equality) rather than like IEEE defined numbers. It's an extra element that isn't part of the problem the numeric standards are trying to solve. Cheers, Nick. -- Nick Coghlan | ncoghlan at gmail.com | Brisbane, Australia ---------------------------------------------------------------
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