> From: Thomas Lumley [mailto:[EMAIL PROTECTED]
>
> 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
>
On our Opteron I get:
> NA+NaN
[1] NaN
> NaN+NA
[1] NA
OK, now I'm really confused...
Andy
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