[Rd] is.numeric (NA + NA) is TRUE, should be FALSE (PR#8745)

[cfillekes at gmail.com]

Full_Name: c fillekes
Version: Version 2.2.1  (2005-12-20 r36812)
OS: Gentoo Linux kernel 2.6.12
Submission from: (NULL) (129.116.71.233)




"Not Available" is of course not a numeric: 
R

> is.numeric (NA)
[1] FALSE

But for some reason, all arithmetic operations on NA's are
in fact numeric, even if it's with other NA's.  


> is.numeric (NA+NA)
[1] TRUE
> is.numeric (NA^2)
[1] TRUE
> is.numeric (NA-NA)
[1] TRUE
> is.numeric (NA*NA)
[1] TRUE
> is.numeric (NA/NA)
[1] TRUE
>

This is not the expected thing.