Question

I would like to ask how can we get a value of a function which is embedded in another function, as in the following example:

message <- function() {
    inside.message <- function() {
        return("inside.message")
    }   
}

run.f <- function() {
    return.inside.mesage <- message()
    print(return.inside.mesage)
}           

run.f() # We do not get "inside.message"

Thank you in advance, all of you

Answer 1

As you wrote it, the function message returns a function, which if evaluated will return “inside.message”. So there are a couple ways to get R to print “inside.message”.

First way:

In the message function, add the line return(inside.message()) so that the function inside.message is evaluated and the result is returned, instead of returning the function itself:

message <- function() {
  inside.message <- function() {
    return("inside.message")
  }
  return(inside.message())
}

message()
# "inside.message"

Then evaluating run.f() will also print “inside.message”.

The second way:

Leave message as you have it and change run.f() to the following

run.f <- function() {
  return.inside.mesage <- message()
  print(return.inside.mesage())
}

Above, you assign the function returned by message() to the object return.inside.message and then evaluate that function.