Exponentiation in C (was: How not to write a loop)

[msf at prandtl.nas.nasa.gov.UUCP]

In article <3167 at ritcsh.UUCP> gregory at ritcsh.UUCP (Gregory Conway) writes:
>I'm still a little wet behind the ears where C is concerned, so (politely)
>correct me if I'm wrong, but what's wrong with this:
>
>		y = 3.0^2
>		log (y) = log (3.0^2)
>		log (y) = 2 * log(3.0)
>
>		So......
>
>		y = exp ((double)2 * log(3.0));
>
>Mathematically, it should work.  I'm just not so sure that it will compile.
>How about it??

Well, it didn't compile.  After adding semicolons and a few other dew dads,
just to see what would come out, I got this:
main()
{
        union   {
                int     a;
                float   b;
        } y;

        y.b = 3.0;

        printf("%f\n", (float) (y.a ^ 2));
}

and the answer was 1077936130.000000.  I had to throw in the union 'cause
otherwise the compiler barfed on doing exclusive-or on a float.  :-)
		mike


Michael Fischbein                 msf at ames-nas.nas.nasa.gov
                                  ...!seismo!decuac!csmunix!icase!msf
These are my opinions and not necessarily official views of any
organization.