Review Request: KColorSpace::KHCY::KHCY(const & QColor) constructor floating point precision error

Oswald Buddenhagen ossi at
Tue Jun 23 06:52:18 BST 2009

On Mon, Jun 22, 2009 at 07:15:39PM -0400, Michael Pyne wrote:
> On Monday 22 June 2009 17:53:54 Michael Kreitzer wrote:
> > I considered that as well. The only thing that worries me is IEEE 754 on
> > x86 seems woefully unreliable for direct comparisons if you're not trying
> > to do something very simple (e.g. prevent a divide by zero).
> In all fairness, floating point on pretty much any platform is not suitable 
> for comparing to equality with anything but 0.0.  For floating point if you 
> must compare something being equal to another value you should allow some 
> tolerance (i.e. is it within 1e-5, not is it exactly equal to something).

> I think the best answer in this case is to ensure as much as possible, 
> comparisons are done against 0.0 (i.e. don't do if (a == b), but do c = a - b; 
> if(c == 0.0) )
i really have to wonder what the technical foundation of that idea is,
because to me it doesn't make any sense.

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