[Rd] External special functions (SPECIALSXP)

Peter Danenberg pcd at roxygen.org
Wed May 25 20:05:47 CEST 2011

> However, if you don't want to evaluate the arguments, just pass
> substitute(arg) to your function instead of arg.

Thanks, Duncan; the problem is, I'm trying to substitute on `...' and
I don't think I can access `...' without inadvertently evaluating it.

I'm trying to write a debugging function which, given any number of
expressions, prints the expression next to its evaluation.

This is trivial to do in the single arity case:

  debug <- function(expression) {
    cat(substitute(expression), expression, "\n")

  a <- 2

  a 2

but I'm not sure how to make it work with variable arity without
resorting to SPECIALSXP.

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