Subject: Re: floating point negative zero
To: Terry Moore <tmm@mcci.com>
From: David Laight <david@l8s.co.uk>
List: tech-userlevel
Date: 08/25/2007 08:50:11
On Fri, Aug 24, 2007 at 05:19:50PM -0400, Terry Moore wrote:
> According to ISO C-1999 page 275, section 7.19.6.1, note 233:
> 
> "The results of all floating conversions of a negative zero, and of 
> negative values that round to zero, include a minus sign".

Maybe the word 'round' is intended to be significant ?

so
	for (a = -1.0; a != 0.0; a /= 10.0);
would give -0, but
	a = -1.0; a *= 0.0;
would generate 0 because there is no rounding error.
Probably
	for (a = -1.0; a != 0.0; a /= 10.0);
	b = 1.0; b *= a;
is required to generate -0.

	David

-- 
David Laight: david@l8s.co.uk