R devel - Dec 2013 - RHS of assignment is evaluated eagerly?

Is this expected behavior, and if so, why? I would have expected
neither 'arg' nor 'value' to evaluate until forced.

`test<-` <- function(obj, arg, value) {
  1 #force no args
}
x <- 1
test(x, print("evaled arg")) <- print("evaluated value")

## [1] "evaluated value"

Peter

On Dec 26, 2013, at 10:26 PM, Peter Meilstrup <peter.meilstrup at
gmail.com> wrote:
> Is this expected behavior, and if so, why? I would have expected
> neither 'arg' nor 'value' to evaluate until forced.
> 
> `test<-` <- function(obj, arg, value) {
>  1 #force no args
> }
> x <- 1
> test(x, print("evaled arg")) <- print("evaluated
value")
> 
> ## [1] "evaluated value?
> 
?Use the source, Luke?:

    /*  It's important that the rhs get evaluated first because
        assignment is right associative i.e.  a <- b <- c is parsed as
        a <- (b <- c).  */

Compare to
> `test<-`(x, print("evaled arg"), print("evaluated
value"))
[1] 1

Cheers,
Simon