Re: [R] How to share variables

From: Sergio Martino <s.martino_at_tno.it>
Date: Tue 22 Aug 2006 - 19:45:01 EST

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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