Hi,>From the R user manual, I have a basic understanding of the scope of function evaluation but have a harder time understanding how to mess with environments.My problem can be summarized by the code shown at the bottom: - the foo function performs some steps including the assignment of default values to 3 objects: x, y, z - at some point, I would like to call either the bar1 or bar2 function based upon the value of the c argument of the foo function. These functions assign different values to the x, y, z variables. - then foo should move on and do other cool stuff Based upon default R scoping, the x, y, and z variables inside the bar1 and bar2 functions are not in the same environment as the x, y, and z variables created inside the foo function. Can I modify the scope of evaluation of bar1 and bar2 so that x, y, and z created inside the foo function are modified? PS: - I know about "<<-" but, in my real code (which I cannot share, sorry), foo is already called within other functions and x, y, and z variables do not exist in the top-level environment and are not returned by foo. So "<<-" does not work (per manual: " Only when <<- has been used in a function that was returned as the value of another function will the special behavior described here occur. ") - In my real example, I have a few dozens of variables to transform in bar1 and bar2 so exporting a list bundling all the transform values then dispatching them in foo does not seem practical - currently, my best solution is to save the inner part of bar1 and bar2 in separate scripts and sourcing them in foo (that does not seem elegant...) - also, I know that, theoretically, I could put the content of bar1 and bar2 directly in foo, but as the number of cases handled by foo grows, the code will become way too long and hardly manageable. Thanks for your help ###################################### bar1 <- function(){ x <- 1 y <- 1 z <- 1 cat(sprintf('bar1: x=%d, y=%d, z=%d\n', x, y, z)) } bar2 <- function(){ x <- 2 y <- 2 z <- 2 cat(sprintf('bar2: x=%d, y=%d, z=%d\n', x, y, z)) } foo <- function(a=1, b=2, c=0){ # some setup code dummy <- a + b x <- y <- z <- 0 # here is my scope problem if (c==1) bar1() if (c==2) bar2() # some more code cat(sprintf('foo: x=%d, y=%d, z=%d\n', x, y, z)) } foo(c=0) foo(c=1) foo(c=2)
On 30/10/2018 3:56 PM, Sebastien Bihorel wrote:> Hi, > > From the R user manual, I have a basic understanding of the scope of function evaluation but have a harder time understanding how to mess with environments. > > My problem can be summarized by the code shown at the bottom: > - the foo function performs some steps including the assignment of default values to 3 objects: x, y, z > - at some point, I would like to call either the bar1 or bar2 function based upon the value of the c argument of the foo function. These functions assign different values to the x, y, z variables. > - then foo should move on and do other cool stuff > > Based upon default R scoping, the x, y, and z variables inside the bar1 and bar2 functions are not in the same environment as the x, y, and z variables created inside the foo function. > > Can I modify the scope of evaluation of bar1 and bar2 so that x, y, and z created inside the foo function are modified? > > PS: > - I know about "<<-" but, in my real code (which I cannot share, sorry), foo is already called within other functions and x, y, and z variables do not exist in the top-level environment and are not returned by foo. So "<<-" does not work (per manual: " Only when <<- has been used in a function that was returned as the value of another function will the special behavior described here occur. ")I haven't looked up that quote, but it is likely describing a situation that isn't relevant to you. For you, the important part is that bar1 and bar2 must be created within foo. They don't need to be returned from it. So my edit below of your code should do what you want. foo <- function(a=1, b=2, c=0){ bar1 <- function(){ x <<- 1 y <<- 1 z <<- 1 cat(sprintf('bar1: x=%d, y=%d, z=%d\n', x, y, z)) } bar2 <- function(){ x <<- 2 y <<- 2 z <<- 2 cat(sprintf('bar2: x=%d, y=%d, z=%d\n', x, y, z)) } # some setup code dummy <- a + b x <- y <- z <- 0 # here is my scope problem if (c==1) bar1() if (c==2) bar2() # some more code cat(sprintf('foo: x=%d, y=%d, z=%d\n', x, y, z)) } foo(c=0) foo(c=1) foo(c=2) I get this output: > foo(c=0) foo: x=0, y=0, z=0 > foo(c=1) bar1: x=1, y=1, z=1 foo: x=1, y=1, z=1 > foo(c=2) bar2: x=2, y=2, z=2 foo: x=2, y=2, z=2 Duncan Murdoch
Hi Sebastien,
I like Duncan's response. An alternative approach is to pass around
environments, as in the following:
bar1 <- function(e) {
e$x <- e$y <- e$z <- 1
cat(sprintf('bar1: x=%d, y=%d, z=%d\n', e$x, e$y, e$z))
}
bar2 <- function(e) {
e$x <- e$y <- e$z <- 2
cat(sprintf('bar2: x=%d, y=%d, z=%d\n', e$x, e$y, e$z))
}
foo <- function(a=1, b=2, c=0, e){
# some setup code
dummy <- a + b
e$x <- e$y <- e$z <- 0
# here is my scope problem
if (c==1) bar1(e)
if (c==2) bar2(e)
# some more code
cat(sprintf('foo: x=%d, y=%d, z=%d\n', e$x, e$y, e$z))
}
e <- new.env()
e$x <- NA
e$y <- NA
e$z <- NA
foo(c=0,e=e)
foo(c=1,e=e)
foo(c=2,e=e)
HTH,
Eric
On Tue, Oct 30, 2018 at 10:13 PM Duncan Murdoch <murdoch.duncan at
gmail.com>
wrote:
> On 30/10/2018 3:56 PM, Sebastien Bihorel wrote:
> > Hi,
> >
> > From the R user manual, I have a basic understanding of the scope of
> function evaluation but have a harder time understanding how to mess with
> environments.
> >
> > My problem can be summarized by the code shown at the bottom:
> > - the foo function performs some steps including the assignment of
> default values to 3 objects: x, y, z
> > - at some point, I would like to call either the bar1 or bar2 function
> based upon the value of the c argument of the foo function. These functions
> assign different values to the x, y, z variables.
> > - then foo should move on and do other cool stuff
> >
> > Based upon default R scoping, the x, y, and z variables inside the
bar1
> and bar2 functions are not in the same environment as the x, y, and z
> variables created inside the foo function.
> >
> > Can I modify the scope of evaluation of bar1 and bar2 so that x, y,
and
> z created inside the foo function are modified?
> >
> > PS:
> > - I know about "<<-" but, in my real code (which I
cannot share, sorry),
> foo is already called within other functions and x, y, and z variables do
> not exist in the top-level environment and are not returned by foo. So
> "<<-" does not work (per manual: " Only when <<-
has been used in a
> function that was returned as the value of another function will the
> special behavior described here occur. ")
>
> I haven't looked up that quote, but it is likely describing a situation
> that isn't relevant to you. For you, the important part is that bar1
> and bar2 must be created within foo. They don't need to be returned
> from it.
>
> So my edit below of your code should do what you want.
>
> foo <- function(a=1, b=2, c=0){
>
> bar1 <- function(){
> x <<- 1
> y <<- 1
> z <<- 1
> cat(sprintf('bar1: x=%d, y=%d, z=%d\n', x, y, z))
> }
>
> bar2 <- function(){
> x <<- 2
> y <<- 2
> z <<- 2
> cat(sprintf('bar2: x=%d, y=%d, z=%d\n', x, y, z))
> }
>
> # some setup code
> dummy <- a + b
> x <- y <- z <- 0
>
> # here is my scope problem
> if (c==1) bar1()
> if (c==2) bar2()
>
> # some more code
> cat(sprintf('foo: x=%d, y=%d, z=%d\n', x, y, z))
>
> }
>
> foo(c=0)
> foo(c=1)
> foo(c=2)
>
> I get this output:
>
> > foo(c=0)
> foo: x=0, y=0, z=0
> > foo(c=1)
> bar1: x=1, y=1, z=1
> foo: x=1, y=1, z=1
> > foo(c=2)
> bar2: x=2, y=2, z=2
> foo: x=2, y=2, z=2
>
> Duncan Murdoch
>
> ______________________________________________
> R-help at 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]]
Thanks Duncan for your quick reply. Ideally, I would want bar1 and bar2 to be independent functions, because they are huge in actuality and, as the actual foo function grows, I may end up with 10 different bar# functions. So I would like to separate them from foo as much as possible. ----- Original Message ----- From: "Duncan Murdoch" <murdoch.duncan at gmail.com> To: "Sebastien Bihorel" <sebastien.bihorel at cognigencorp.com>, r-help at r-project.org Sent: Tuesday, October 30, 2018 4:13:05 PM Subject: Re: [R] Question about function scope On 30/10/2018 3:56 PM, Sebastien Bihorel wrote:> Hi, > > From the R user manual, I have a basic understanding of the scope of function evaluation but have a harder time understanding how to mess with environments. > > My problem can be summarized by the code shown at the bottom: > - the foo function performs some steps including the assignment of default values to 3 objects: x, y, z > - at some point, I would like to call either the bar1 or bar2 function based upon the value of the c argument of the foo function. These functions assign different values to the x, y, z variables. > - then foo should move on and do other cool stuff > > Based upon default R scoping, the x, y, and z variables inside the bar1 and bar2 functions are not in the same environment as the x, y, and z variables created inside the foo function. > > Can I modify the scope of evaluation of bar1 and bar2 so that x, y, and z created inside the foo function are modified? > > PS: > - I know about "<<-" but, in my real code (which I cannot share, sorry), foo is already called within other functions and x, y, and z variables do not exist in the top-level environment and are not returned by foo. So "<<-" does not work (per manual: " Only when <<- has been used in a function that was returned as the value of another function will the special behavior described here occur. ")I haven't looked up that quote, but it is likely describing a situation that isn't relevant to you. For you, the important part is that bar1 and bar2 must be created within foo. They don't need to be returned from it. So my edit below of your code should do what you want. foo <- function(a=1, b=2, c=0){ bar1 <- function(){ x <<- 1 y <<- 1 z <<- 1 cat(sprintf('bar1: x=%d, y=%d, z=%d\n', x, y, z)) } bar2 <- function(){ x <<- 2 y <<- 2 z <<- 2 cat(sprintf('bar2: x=%d, y=%d, z=%d\n', x, y, z)) } # some setup code dummy <- a + b x <- y <- z <- 0 # here is my scope problem if (c==1) bar1() if (c==2) bar2() # some more code cat(sprintf('foo: x=%d, y=%d, z=%d\n', x, y, z)) } foo(c=0) foo(c=1) foo(c=2) I get this output: > foo(c=0) foo: x=0, y=0, z=0 > foo(c=1) bar1: x=1, y=1, z=1 foo: x=1, y=1, z=1 > foo(c=2) bar2: x=2, y=2, z=2 foo: x=2, y=2, z=2 Duncan Murdoch
Here's another modification to your code that also works. It's a lot
uglier, but will allow bar1 and bar2 to be used in multiple functions,
not just foo.
bar1 <- function(env){
env$x <- 1
env$y <- 1
env$z <- 1
with(env, cat(sprintf('bar1: x=%d, y=%d, z=%d\n', x, y, z)))
}
bar2 <- function(env){
env$x <- 2
env$y <- 2
env$z <- 2
with(env, cat(sprintf('bar2: x=%d, y=%d, z=%d\n', x, y, z)))
}
foo <- function(a=1, b=2, c=0){
# some setup code
dummy <- a + b
x <- y <- z <- 0
# here is my scope problem
if (c==1) bar1(environment())
if (c==2) bar2(environment())
# some more code
cat(sprintf('foo: x=%d, y=%d, z=%d\n', x, y, z))
}
foo(c=0)
foo(c=1)
foo(c=2)
Duncan Murdoch
That's cool! I think this solution would fit better with what my intended
setup.
Thanks a lot
----- Original Message -----
From: "Duncan Murdoch" <murdoch.duncan at gmail.com>
To: "Sebastien Bihorel" <sebastien.bihorel at cognigencorp.com>,
r-help at r-project.org
Sent: Tuesday, October 30, 2018 4:18:51 PM
Subject: Re: [R] Question about function scope
Here's another modification to your code that also works. It's a lot
uglier, but will allow bar1 and bar2 to be used in multiple functions,
not just foo.
bar1 <- function(env){
env$x <- 1
env$y <- 1
env$z <- 1
with(env, cat(sprintf('bar1: x=%d, y=%d, z=%d\n', x, y, z)))
}
bar2 <- function(env){
env$x <- 2
env$y <- 2
env$z <- 2
with(env, cat(sprintf('bar2: x=%d, y=%d, z=%d\n', x, y, z)))
}
foo <- function(a=1, b=2, c=0){
# some setup code
dummy <- a + b
x <- y <- z <- 0
# here is my scope problem
if (c==1) bar1(environment())
if (c==2) bar2(environment())
# some more code
cat(sprintf('foo: x=%d, y=%d, z=%d\n', x, y, z))
}
foo(c=0)
foo(c=1)
foo(c=2)
Duncan Murdoch