[vox-tech] location of DBL_EPSILON definition

Peter Jay Salzman p at dirac.org
Fri Jan 26 11:36:34 PST 2007


On Fri 26 Jan 07,  8:39 AM, Micah Cowan <micah at cowan.name> said:
> On Fri, 2007-01-26 at 08:24 -0500, Peter Jay Salzman wrote:
> > Where is DBL_EPSILON defined?  I thought it was in float.h.  But I've looked
> > at float.h in:
> > 
> >    /usr/lib/gcc-lib/i486-linux-gnu/3.3.6/include
> >    /usr/lib/gcc/i486-linux-gnu/3.4.6/include
> > 
> > and neither one actually defined it.
> > 
> > Where is the numerical value held?
> 
> All you really need to worry about is that it gets defined when you
> #include <float.h>.
> 
> My float.h simply defines DBL_EPSILON to __DBL_EPSILON__. There does not
> appear to be an inclusion of some other file, or a definition of
> __DBL_EPSILON__. So the answer to your question would seem: compiler
> magic. :)
 
This is very unfortunate.  I liked having one file to look at for all my
float constant curiosity.


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