[R] system.time gives error when "=" is used for assignment (R-2.6.0)

[Kyeongmi Cheon]

Hello list,
I found that system.time works correctly when I used "<-" to assign a
value to a variable but when I happened to use "=" instead of "<-", R
gave an error message:
"Error in system.time(your argument here...)". It happened with a few
functions I tried. Is this a bug or is there any circumstances that
"=" cannot be used for assignment? Here is a real simple example.

fn1 <- function(x) x+1

r1 <- system.time(res1=fn1(2))
r2 <- system.time(res2 <- fn1(2))


Thank you.
Kyeongmi
University of Memphis