[R] How to share variables
Sergio Martino
s.martino at tno.it
Tue Aug 22 11:45:01 CEST 2006
Hi
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
memory?
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 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$dat)
> myfun(10)
>
Hit!!!
It solves the problem.
A small drawback is that I need to modify the name of each occurrence of the
variable.
> # or passing e explicitly
>
> myfun2 <- function(x, e) sum(x + e$dat)
> myfun2(10, e)
>
Any overhead in passing the environment? Is it a pointer?
Sergio
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