I have re-read the 'Writing R Extensions' manual. It seems to me that it clearly says R API functions can be called from from C++ programs, and the API includes the special values ISNAN() and R_FINITE() and the missing test ISNA().
R_FINITE is no problem. It is defined as R_finite, which is declared in Rmath.h and included in libRmath.
ISNAN() however is broken.
In R 1.9 it was defined as R_IsNaNorNA unless IEEE_754 was defined which was not done in the standalone libRmath/Rmath.h. R_IsNaNorNA was declared in Rmath and included in libRmath. So it would work, although probably not when built against an installed R library because R.h would likely define IEEE_754.
In R2.0 ISNAN() is defined using isnan thus (isnan(x)!=0). isnan() is in math.h and this works perfectly for C code. However, in C++ the header cmath (included by iostream and others) undefs isnan(). So on platforms for which isnan() is a macro, the code breaks at compile time with 'isnan() undeclared'.
If building against a full R library, one might possible use R_IsNaN instead but this function is not included in libRmath v2.0 and the function R_IsNaNorNA which was used in libRmath v1.9 no longer exists
While I am on this topic, there seems to be nothing at all in the standalone libRmath to deal with ISNA() and although R_PosInf and R_NegInf are in the library, they don't seem to me to be declared.
Bill Northcott
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