On Wed, Mar 24, 2010 at 2:50 PM, Mark Dickinson <dicki...@gmail.com> wrote: > On Wed, Mar 24, 2010 at 6:26 PM, Alexander Belopolsky > <alexander.belopol...@gmail.com> wrote: >> Mark, I wonder if you could describe an algorithm off the top of your >> head that relies on NaN == NaN being false. >> > > No, I certainly couldn't! And I often wonder if the original IEEE 754 > committee, given 20/20 foresight, would have made the same decisions > regarding comparisons of nans. It's certainly not one of my favourite > features of IEEE 754.
I tried to google the rationale for the IEEE 754 decision, but came up with nothing. Here are a few representative results: """ So without fear let me not stop at the arguments that “the committee must have voted on this point and they obviously knew what they were doing” and “it is the standard and implemented on zillions of machines, you cannot change it now”. """ - "Reflexivity, and other pillars of civilization" by Bertrand Meyer http://bertrandmeyer.com/2010/02/06/reflexivity-and-other-pillars-of-civilization/ """ I suppose this simplifies numerical computations in some way, but I couldn't find an explicitly stated reason, not even in the Lecture Notes on the Status of IEEE 754 by Kahan which discusses other design decisions in detail. """ - "What is the rationale for all comparisons returning false for IEEE754 NaN values?" http://stackoverflow.com/questions/1565164/what-is-the-rationale-for-all-comparisons-returning-false-for-ieee754-nan-values _______________________________________________ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
