[Rd] unexpected behaviour when defining a function

Deepayan Sarkar deepayan.sarkar at gmail.com
Tue Sep 12 01:26:24 CEST 2006


I know S manuals used to warn against using the same names for a
variable and a function, but I have never seen that cause problems in
R, so I usually don't pay much attention to it. Which is why the
following behaviour came as a surprise:

> bar <- function() 1
> foo <- function(bar = bar()) {
+     bar
+ }
> foo(9)
[1] 9
> foo()
Error in foo() : recursive default argument reference

Exactly what rule am I violating here?

The following gives a slightly different error, but I assume it has a
similar origin:

bar <- function() 1
foo <- function(bar) {
    if (missing(bar)) bar <- bar()

This version works fine though (so the rule probably involves function
arguments somehow):

foo <- function(baz) {
    if (missing(baz)) {
        baz <- function() 2
        baz <- baz()


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