print if not assigned

Question

How can I write into a function a way to detect if the output is being assigned (<-) to something? The reasoning is I\'d like to print a message if it is no

Answer 1

I love Josh's idea but for future posters wanted to show what I did which is a slightly modified version of his approach. His approach prints out the class information which is the only thing I didn't like. He used the NextMethod to avoid the infinite recursion printing. This causes the

attr(,"class")
[1] "myClass"

to be printed. So to avoid this I print the message first and then print 1 through the length of the class object (using indexing).

fun <- function(x) {
    class(x) <- 'beep'
    comment(x) <- "hello world"
    return(x)
}

print.beep<- function(beep) {
    cat(paste0(comment(beep), "\n"))
    print(beep[1:length(beep)])
}


> fun(1:10)
hello world
 [1]  1  2  3  4  5  6  7  8  9 10

Thanks again Josh for the idea.

If the reader didn't want the little [1] index to print either they could cat the output int he print statement as:

print.beep<- function(beep) {
    cat(paste0(comment(beep), "\n"))
    cat(beep[1:length(beep)], "\n")
}