[R] Canonical method for S engine selection?

[Thomas Lumley]

On Wed, 6 Dec 2006, Paul Roebuck wrote:

> Assuming script 'common.q' contains code that needed
> different processing depending on interpreter
> (either S-PLUS or R), what should the condition be?
>

I believe
   exists("is.R") && is.R()
is a reliable condition.

 	-thomas