Making data accessible in functions

Suppose you wanted to create a function that can access certain data, but you do not wish to pass the data as an argument. Rather, you would like to `equip' the function with the data. The function provide will do just that.

provide <- function(f, provision) {
  environment(f) <-
    list2env(provision, parent = environment(f))

It will take a function f and a list provision, and make the data in provision accessible in f. Here is an example function.

fun <- function(x)
    x + a

Let us try fun.

a <- 2

Suppose we wanted to fix the value of a.

fun2 <- provide(fun, list(a = 41))

Let us try fun2.

a <- 2