On Wed, 17 Mar 2004, Liaw, Andy wrote:
> Dear R-devel,
>
> Has anyone seen this problem? We tried building R-1.8.1 (and R-1.9.0 alpha
> 2004-03-17) on an Irix 6.5 box using
>
> ./configure CC="cc -64" F77="f77 -64" --with-tcltk=no --enable-R-shlib
>
> make check failed because NA + 0 gave NaN instead of NA. I've tried both
> 32- and 64-bit build, with and without --enable-R-shlib. The same symptom
> occur in all cases.
>
I haven't seen it before, but it looks to me as though arithmetic.c
assumes that adding a number to a NaN gives the same NaN back, (NA is the
NaN with lower word 1954). That is, we just do
#ifdef IEEE_754
REAL(ans)[i] = REAL(s1)[i1] + REAL(s2)[i2];
#else
This doesn't look as thought it is guaranteed to work, though it does on
most machines. It clearly can't work where both operands are NaN, so
under OS X I get
> NA+NaN
[1] NA
> NaN+NA
[1] NaN
-thomas
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