[R] on lexical scoping....

[Mark Leeds]

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.
>

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