On 25/05/2011 1:10 PM, Peter Danenberg wrote:
Is it possible to define an external special function (SPECIALSXP)?
I'm trying to do some language-level work, and don't want my arguments
evaluated before they hit C.
It looks like the only way to define a SPECIALSXP is by using XX0 in
the `eval' field of R_FunTab; is there any way to make this applicable
to externally defined functions?
I don't think so. However, if you don't want to evaluate the arguments,
just pass substitute(arg) to your function instead of arg. For example,
f <- function(a, b) {
print(substitute(b))
print(substitute(a))
}
f( x <- 1, y <- 2 )
will print but never evaluate the assignments.
Duncan Murdoch
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