The R Project SVN R

##-- This REALLY does  NOT work in R (0.62, April 9, 1998) !!!
##-- just call  abc.default(..)  ...

abc <- function(x, ...) {
  if (is.null(class(x))) class(x) <- data.class(x)
  cat("abc: Before dispatching; x="); str(x)
  ##fails:
  UseMethod("abc")
  ##fails in all cases: NextMethod("abc",x)
}
abc.default <- function(x, ...) sys.call()

"abc.(" <- function(x)
  cat("'(' method of abc:", deparse(sys.call(sys.parent())),"\n")

abc.expression <- function(x)
  cat("'expression' method of abc:", deparse(sys.call(sys.parent())),"\n")

abc(1)
e0 <- expression((x))
e1 <- expression(sin(x))
abc(e0)
abc(e1)
abc(e0[[1]])
abc(e1[[1]])