[R] provide extra variables to environment in call

[Khamenia, Valery]

Hi all,

Situation: 

 there is a function `f' already defined by someone and 
 provided in package. `f' looks like that:

  f <- function() {
    x+1
  }

 i.e. `f' is not closed i.r.t. term `x'

 now I have my own function `g', where I'd like
 to override variable `x' while calling `f':

  x <- "dummy gloabal value"

  g <- function() {
    x <- 42
    eval(f(), environment()) # how to make loacl `x' visible in `f'?
  }

  g() # => Error in x + 1 : non-numeric argument to binary operator

Here comes the question:

 What is the right way to call `f' in order to override 
 global value of `x' with the local value defined within 
 of function `g' ?

I see that i've missed something in docs for eval/environments and related.

Thank you in advance.
--
Valery.