Date: Fri, 18 Nov 1994 08:15:16 -0700
To: djgpp AT sun DOT soe DOT clarkson DOT edu
From: gordon AT spot DOT colorado DOT edu (Allen Gordon)
Subject: Re: printf or floating point error?????


I believe the following is a problem with printf.  Please advise.
Thanks

Allen Gordon

*******************************************************



#include 	<stdio.h>
#include	<math.h>
void main(void)
{
	float ans,num,inv;
	double ansd, numd,invd;
	long double ansld,invld,numld;
	num = 824633702441.0;
	numd = ( double)824633702441.0;
	numld = (long double) 824633702441.0;

	inv = 1.0 / num;
	invd = (double) 1.0 /  numd;
	invld = (long double) 1.0 / numld;

	ansld = numld * invld;
	ansd = numd*invd;
	ans = num * inv;

	printf("%20.18g\t%20.18g\t%20.18g \n", num, inv, ans);
	printf("%20.18g\t%20.18g\t%20.18g \n", numd,invd, ansd);
	printf ("%20.18Lg\t%20.18Lg\t%20.18Lg \n",numld,invld,ansld);
}


RESULTS:
        824633720832	1.21265963850397673e-12	                      1
        824633702441	1.21265962940866734e-12	   0.999999999999999822
-1.99993148818612099	-1.10101976021228642e-278  3.46811918756373849e-310

Under turbo c(dos) version 3.0, I got:
        824633720832	1.21265963850397673e-12	                   1
         824633702441	1.21265962489115788e-12	0.999999996274709813
        824633702441	1.2126596248911578e-12	0.999999996274709702



Thanks

Allen