Calculation returning NaN
Joe Porkka
jap at convex.cl.msu.edu
Tue Jan 29 05:49:19 AEST 1991
fineberg at caip.rutgers.edu (Adam B. Fineberg) writes:
>I was wondering if someone could point me to a source of information
>about the math error NaN. I understand that this means not a number
I've got to motorola handbook right here....
(If you want the manual, call 1-800-555-1212 to ask for morola number, call
morola and ask for m68000 programmers reference manual. I thinks its <$10)
Well, if a=Nan, and b= anynumber, then most things like
a<b, a*b, etc... return NaN.
On page 1-37 theres a nifty table for the FADD instruction
source in range | zero | infinity
+ - + - + -
=====================================================================
destination
+
in range add add +inf -inf
-
+ +0.0 +-0.0
zero add +inf -inf
- +-0.0 -0.0
+ +inf +inf +inf NaN
infin.
- -inf -inf NaN -inf
So if a=-inf and b=+inf, result = NaN
+inf +inf result = +inf
Also, things like 4.0/0.0 == NaN
More information about the Comp.lang.c
mailing list