[R] Canonical method for S engine selection?

[Paul Roebuck]

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

if (<condition>) {
    # Do S-PLUS code
} else {
    # Do R code
}

Looking for something akin to the C preprocessor directive
USING_R, but for S.

----------------------------------------------------------
SIGSIG -- signature too long (core dumped)