[R] on lexical scoping....

[Jeff Newmiller]

Leading off with you can only have two things in an environment definitely indicates this should be read with a skeptical eye.

Although the title of "Advanced R" may be more scary than someone writing notes on GitHub like a bro, IMHO Adv R is quite readable for anyone interested in questions like this with fewer wrong assertions to unlearn later.

On April 4, 2023 4:53:38 PM PDT, Mark Leeds <markleeds2 using gmail.com> wrote:
>obviously, everyone has different opinions on what's useful but I always
>found this document quite
>helpful. I think, in the past, someone said that there are some incorrect
>statements in but I'm not sure
>what they are.
>
>https://askming.github.io/study_notes/Stats_Comp/Note-How%20R%20searches%20and%20finds%20stuff.html
>
>
>On Tue, Apr 4, 2023 at 7:06 PM Bert Gunter <bgunter.4567 using gmail.com> wrote:
>
>> 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]]
>>
>> ______________________________________________
>> 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]]
>
>______________________________________________
>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.

-- 
Sent from my phone. Please excuse my brevity.