[Rd] Constants

Fabrizio Cipollini cipollin at ds.unifi.it
Mon Oct 15 15:00:55 CEST 2007

Dear R developers

I wrote a package whose computational 'engine' is programmed in Fortran 77.
However, I used also C code, mainly for exploiting the Mathlib Standalone
set of functions.

I successfully compiled and used my package for months, under R-2.4.1 
(and MINGW - GCC 3.4.2).

Now, I switched to R-2.6.0 (and the 'Rtool.exe' set of Murdoch, 
installed EXACTLY
as in its prescriptions) and I encountered problems during compilation.
In a C function I use the DOUBLE_EPS constant (of course, I loaded 
the <R_ext/Constants.h> header).
but the the 'R CMD check' say that
CFunctions1.c:333: error: `DBL_EPSILON' undeclared (first use in this function)

I suspect that the difference between my two compilation experiences 
lies in the different structure
of the <float.h> header between GCC 3.4.2 and GCC 3.4.5.
I'm not a C expertise and hence the question: There is a clean way 
for using this
kind of constants (DOUBLE_EPS and other similar) as my previous experience?

Thanks a lot in advance

P.S. I have a Pentium Centrino and Windows XP.

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