NaN again - and IEEE arithmatics

Mark C Favas mark at chem.uwa.edu.au
Sat May 13 14:56:37 CEST 2000


"Tim Peters" <tim_one at email.msn.com> writes:

>THere's nothing you can do that's guaranteed to work.  Here's a way to make
>a NaN that's quite *likely* to work on any IEEE-754 platform, though:

>>>> Inf = 1e300**2
>>>> NaN = Inf - Inf
>>>> NaN
>-1.#IND
>>>> Inf
>1.#INF
>>>>

>Since that was a Windows session, that's how Microsoft happens to spell NaN
>and infinity these days.

Unfortunately, on a real <0.3 wink> operating system (Tru64 Unix on Compaq
Alpha) this code fragment produces a core dump:

Python 1.6a2 (#99, May 12 2000, 08:21:33) [C] on osf1V4
Copyright 1991-1995 Stichting Mathematisch Centrum, Amsterdam
Copyright 1995-2000 Corporation for National Research Initiatives (CNRI)
>>> Inf = 1e300**2
Floating exception (core dumped)

Cheers,
	Mark
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Email  - mark at chem.uwa.edu.au      ,-_|\                           Mark C Favas
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