Question

I need to load a custom function from an extern file but without causing side-effects.

Currently, I’m doing in this way:

src <- "function(x,y) { return(x + y) }"
# parse the source
ptree <- parse(text=src)
# execute the evaluation using a data.frame as environment (like a sandbox)
f <- eval(ptree, envir=data.frame()) 
if(!is.function(f))
  stop('The given source does not contain a valid function')
f(1,1)

In this way, a “malicious” code does not affect the current environment, e.g. :

src <- "a <- 1" 

so, an existing "a" variable will not be changed by the eval function.

Do you see any drawbacks in this ?
Are there better ways ?

Thanks in advance

Answer 1

You can store your function in a custom environment. You can access it by specifying the environment.

llamegid <- new.env(parent = baseenv())
f <- function(x) x*x
src <- "function(x,y) { return(x + y) }"
assign("f", src, envir = llamegid)

f
function(x) x*x

get("f", envir = llamegid)
[1] "function(x,y) { return(x + y) }"

exists("f", envir = llamegid)
[1] TRUE