[R] Environment question

[ALBERTO VIEIRA FERREIRA MONTEIRO]

>From the code below:

y <- 1

f1 <- function() { 
  cat("y =", y, "\n") 
}

f2 <- function() { 
  y <- 2
  f1()
}

f3 <- function() {
  y <- 3
  f <- f1
  f()
}

f4 <- function() {
  y <- 4
  f <- function() { cat("y =", y, "\n") }
  f()
}

f1()
f2()
f3()
f4()

Clearly, f1(), f2() and f4() will display "y = 1", "y = 1" and "y = 4",
but, not as much clearly but predictably, f3() also displays "y = 1".

Is there any way to rewrite the code of f3 in such a way that it
displays "y = 3"?

An obvious but cumbersome way would be something like:

f3 <- function() {
  y <- 3
  # write the code of f1 to a temporary file
  dump("f1", "temp.R")
  # read the code of f1
  str <- readLines("temp.R")
  # replace the code that defines function f1 for a code that defines function f
  str <- gsub("f1 <-", "f <-", str)
  # write the new code to the temporary file
  writeLines(str, "temp.R")
  # read the source but use local to get things from f3's environment
  # (with the default local = FALSE, "y" would get the value from globalenv())
  source("temp.R", local = TRUE)
  # ...?
  f()
  # PROFIT!
}
  
Is there a more elegant way to do this?

Alberto Monteiro