match.call with default arguments

Question

As part of a function, I want to output a list of all the arguments and their values, including the default values. For example, a function with these arguments:

<         


        

Answer 1

Here is an attempt to wrap this logic in a reusable function to drop in instead of match.call:

match.call.defaults <- function(...) {
  call <- evalq(match.call(expand.dots = FALSE), parent.frame(1))
  formals <- evalq(formals(), parent.frame(1))

  for(i in setdiff(names(formals), names(call)))
    call[i] <- list( formals[[i]] )


  match.call(sys.function(sys.parent()), call)
}

It looks like it works:

foo <- function(x=NULL,y=NULL,z=2,...) {
  match.call.defaults()
}


> foo(nugan='hand', x=4)
foo(x = 4, y = NULL, z = 2, ... = pairlist(nugan = "hand"))