R scoping: disallow global variables in function

Question

Is there any way to throw a warning (and fail..) if a global variable is used within a R function? I think that is much saver and prevents unintended behaviours

Answer 1

Another way (or style) is to keep all global variables in a special environment:

with( globals <- new.env(), {
  # here define all "global variables"  
  sUm <- 10
  mEan <- 5
})

# or add a variable by using $
globals$another_one <- 42

Then the function won't be able to get them:

sum <- function(x,y){
  sum = x+y
  return(sUm)
}

sum(1,2)
# Error in sum(1, 2) : object 'sUm' not found

But you can always use them with globals$:

globals$sUm
[1] 10

To manage the discipline, you can check if there is any global variable (except functions) outside of globals:

setdiff(ls(), union(lsf.str(), "globals")))