[R] on lexical scoping....

[Bert Gunter]

The following *might* be of use to you. If you can predict what the various
function invocations will do, I think you have a reasonable grasp of how
lexical scoping works in R (contrary or supplementary opinions welcome).
It is the sort of thing you will find in the references also. If this is
all obvious, sorry for wasting your time.
#######################
search()
ls()
dat <- list(x =2)
attach(dat,2)
search()
f <- function(){
   g <- function() x
   x <- 3
   g}
h <- f()
g <- function()x
ls()
h()
g()
detach(dat)
h()
g()

##########################
## Here is what this gives starting with an empty .GlobalEnv.
##################################

> search()
 [1] ".GlobalEnv"        "package:tools"     "package:lattice"
"tools:rstudio"
 [5] "package:stats"     "package:graphics"  "package:grDevices"
"package:utils"
 [9] "package:datasets"  "package:methods"   "Autoloads"
"package:base"
> ls()
character(0)
> dat <- list(x =2)
> attach(dat,2)
> search()
 [1] ".GlobalEnv"        "dat"               "package:tools"
"package:lattice"
 [5] "tools:rstudio"     "package:stats"     "package:graphics"
 "package:grDevices"
 [9] "package:utils"     "package:datasets"  "package:methods"
"Autoloads"
[13] "package:base"
> f <- function(){
+    g <- function() x
+    x <- 3
+    g}
> h <- f()
> g <- function()x
> ls()
[1] "dat" "f"   "g"   "h"
> h()
[1] 3
> g()
[1] 2
> detach(dat)
> h()
[1] 3
> g()
Error in g() : object 'x' not found

-- Bert


On Tue, Apr 4, 2023 at 6:56 AM akshay kulkarni <akshay_e4 using hotmail.com>
wrote:

> Dear Members,
>                              I have the following code typed at the
> console prompt:
>
> y   <-   x*10
>
> X has not been defined and the above code throws an object not found
> error. That is, the global environment does not contain x. Why doesn't it
> look further in the environment stack, like that of packages? There are
> thousands of packages that contain the variable named  x. Of course, that
> happens if the above code is in a function (or does it?).
>
> What concept of R is at work in this dichotomy?
>
> THanking you,
> Yours sincerely,
> AKSHAY M KULKARNI
>
>         [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help using r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

	[[alternative HTML version deleted]]