[vox-tech] location of DBL_EPSILON definition

Micah Cowan micah at cowan.name
Fri Jan 26 08:39:08 PST 2007


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. :)

-- 
Micah J. Cowan
Programmer, musician, typesetting enthusiast, gamer...
http://micah.cowan.name/



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