R Code ignored nargs() if statement

Question

Cannot figure out why R is ignoring nargs() in following

foo <- function(x=NULL) {

  if (nargs() > 1){
    stop("Enter 1 argument only")
  }
  cat("call was ", deparse(match.call()), "\n", sep = "")
}

When I execute foo("a","b"), I get Error in foo("a", "b") : unused argument ("b") instead of Enter 1 argument only.

Please advise

Answer 1

For multiple arguments, we can use three dots (...) and the condition with nargs will evaluate it

foo <- function(...) {

 if (nargs() > 1){
  stop("Enter 1 argument only")
 }
  cat("call was ", deparse(match.call()), "\n", sep = "")
 }

foo("a", "b")

Error in foo("a", "b") : Enter 1 argument only

foo("a")
#call was foo("a")