[R] How to share variables
ggrothendieck at gmail.com
Tue Aug 22 14:32:09 CEST 2006
On 8/22/06, Sergio Martino <s.martino at tno.it> wrote:
> Thanks again. I hope not to waste to much of your time.
> I delete some lines of your answer
> > Each time myfun is run a new environment is created to hold
> > its local variables. The parent of that environment is e in
> > this example by construction. So e and the environment that
> > is temporarily created to hold myfun's variables are distinct.
> This means that the enviroment is duplicated, ie it is present twince in
Each time myfun starts up a new environment comes into being
that contains x and each time it completes that environment is
> I must keep some big variables and it will be a waste of memory; moreover if
> I update a value it will be lost.
If you update a local variable then its lost upon exit (of course you
could return the variable or return the environment inside the
function) but if you update it in e then its not lost.
> > > If I can use inside myfun the variable as e$dat (without changing the
> > > enviroment (no environment(myfun) <- e statement)) than it will be ok.
> > Yes you can. You can either make sure that e is visible to myfun
> > via normal scoping rules or pass it explicitly:
> > e <- new.env()
> > e$dat <- 1:3
> > myfun <- function(x) sum(x + e$dat)
> > myfun(10)
> It solves the problem.
> A small drawback is that I need to modify the name of each occurrence of the
That's why in an earlier example we set the environment of myfun
> > # or passing e explicitly
> > myfun2 <- function(x, e) sum(x + e$dat)
> > myfun2(10, e)
> Any overhead in passing the environment? Is it a pointer?
to experiment with timings.
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