On Wed, Oct 04, 2006 at 12:42:04AM -0400, Tim Peters wrote: > > > If C90 doesn't distinguish -0.0 and +0.0, how can Python? > > > Can you give a simple example where the difference between the two > > is apparent to the Python programmer? > > Perhaps surprsingly, many (well, comparatively many, compared to none > ....) people have noticed that the platform atan2 cares a lot:
Once upon a time, floating-point was used as an approximation to mathematical real numbers, and anything which was mathematically undefined in real arithmetic was regarded as an error in floating- point. This allowed a reasonable amount of numeric validation, because the main remaining discrepancy was that floating-point has only limited precision and range. Most of the numerical experts that I know of still favour that approach, and it is the one standardised by the ISO LIA-1, LIA-2 and LIA-3 standards for floating-point arithmetic. atan2(0.0,0.0) should be an error. But C99 differs. While words do not fail me, they are inappropriate for this mailing list :-( Regards, Nick Maclaren, University of Cambridge Computing Service, New Museums Site, Pembroke Street, Cambridge CB2 3QH, England. Email: [EMAIL PROTECTED] Tel.: +44 1223 334761 Fax: +44 1223 334679 _______________________________________________ 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
