Recommended way for variable scoping [duplicate]

Question

In C and variants, when you have something like this:

{
  tmp1 <- 5
  tmp2 <- 2
  print(tmp1 + tmp2)
}

a 7 will be printed, but the tmp1 and tmp2 variables will be removed from stack once the scope } ends. I sometimes want similar functionality in R so that I do not have to clean up (many) temporary variables after some point in time.

One way to make this work in R is like this:

(function(){
  tmp1 <- 5
  tmp2 <- 2
  print(tmp1 + tmp2)
})()

Now that seems a bit hackish -- or it may be just me.

Are there any better or more concise (i.e. more readable) ways to do this in R?

Answer 1

You might want to use local in base R for that purpose:

local({
  tmp1 <- 5
  tmp2 <- 2
  print(tmp1 + tmp2)
})

So any variable created within the scope of local will vanish as soon as the scope is left.

From ?local:

local evaluates an expression in a local environment.

See ?local for more details.

---

Additionally, with (suggested by @Rich Scriven in the comments) also in base R can be used where 1 is just a dummy data:

with(1, {
    tmp1 <- 5
    tmp2 <- 2
    print(tmp1 + tmp2)
})

From ?with:

with is a generic function that evaluates expr in a local environment constructed from data.