[R-pkg-devel] testing for NaN in C++ code

Ben Bolker bbo|ker @end|ng |rom gm@||@com
Sat Mar 6 03:07:18 CET 2021

   Thanks!  Now I see this is in Writing R Extensions, should have 
looked more carefully ...

On 3/5/21 9:00 PM, Andrew Simmons wrote:
> Hello,
> You probably want one of the following
> ISNA         TRUE for R's NA only
> ISNAN      TRUE for R's and IEEE's NaN
> R_IsNaN   TRUE for IEEE'S NaN only
> On Fri, Mar 5, 2021, 20:55 Ben Bolker <bbolker using gmail.com 
> <mailto:bbolker using gmail.com>> wrote:
>     I would like to test for NaN inside C++ code that lives inside a CRAN
>     package.
>     Following the StackOverflow question linked below, I was using
>     #define isNAN(a)  (a!=a)
>     which I *think* used to work, but at some point along the way it
>     stopped
>     working due to compiler/flag changes. I'm thinking of switching to
>     #define isNAN(a) std::isnan(a)
>     instead. Does anyone have first-hand knowledge of having tried this and
>     know if it works across the range of platforms/standard compilation
>     flags that CRAN/R users are likely to experience?  Any other
>     suggestions?
>        I know that I should follow the problem upstream and detect it where
>     it happens (see the answer titled "nan prevention" on SO), but in the
>     meantime it would be nice to be able to do this robustly across all the
>     platforms it's likely to see.
>         cheers
>           Ben Bolker
>     https://stackoverflow.com/questions/570669/checking-if-a-double-or-float-is-nan-in-c/42138465#42138465
>     <https://stackoverflow.com/questions/570669/checking-if-a-double-or-float-is-nan-in-c/42138465#42138465>
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