[R] attribute and main value

[Gerrit Draisma]

Just a curiosity question:

In the documentation for the nlm procedure
a find this example of defining a function
with a gradient attribute:
-----------
      f <- function(x, a)
      {
          res <- sum((x-a)^2)
          attr(res, "gradient") <- 2*(x-a)
          res
      }
-----------
I get the gradient with
      attr(f(3,2),"gradient")
but how do I get the function value it self?

Gerrit