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
Yes, but in your standalone C or C++ code you can just use isnan() from math.h directly.
As I explained in the last message:
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'.
The reason that R doesn't do that is twofold. In the past we tried to support computers that didn't use IEEE 754 arithmetic, which meant that isnan might not exist. Also, IIRC we found that isnan() doesn't use 1 for TRUE on all platforms -- sometimes it uses -1 or something else -- and code had assumed 1. That's why the strange-looking isnan(x)!=0 is there.
There is nothing strange about this. The spec for isnan says it is zero if and only if the object is not a nan. Any other value indicates a nan.
It would be worth noting somewhere that ISNAN breaks when some C++ headers are included on Mac OS X, and I will do that.
The point I am trying to make is that it is not just MacOS X. The g++ cmath header undefs isnan so it will break with gcc on any platform which has a macro for isnan. HP-UX is one.
Also the C++ gurus insist that the ISO C++ standard requires cmath to zap the macros, which implies it will happen with other ISO compliant C++ compilers.
There is a function R_IsNaN. I have not checked, but I presume it just calls isnan. This should work because it will not be zapped by the C++ headers, because it is in a different (C?) compilation unit. However, it is currently not part of the standalone Rmath.h/libRmath. It would be good if it could be included in the standalone build as was its predecessor R_IsNaNorNA.
That way, we would have a workaround by using R_IsNaN.
Bill Northcott
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