[R] Fwd: Evaluating a function within a pre-defined environment?

[David Reiss]

Ideally I would like to be able to use the function f (in my example)
as-is, without having to designate the environment as an argument, or
to otherwise have to use "e$x" in the function body.

thanks for any further advice...

On Wed, Dec 9, 2009 at 2:36 PM, Gabor Grothendieck
<ggrothendieck at gmail.com> wrote:
> e <- new.env()
> e$x <- 2
> f <- function(a, e) { e$x <- e$x + a; e$x }
> f(3, e)
> e$x # 5
>
> Another way to accomplish this is to use the proto package which puts
> the whole thing into an object oriented framework.  See
> http://r-proto.googlecode.com
>
> library(proto)
> p <- proto(x = 2, f = function(this, a) { this$x <- this$x + a; this$x })
> p$f(3) # 5
>
>
> On Wed, Dec 9, 2009 at 4:54 PM, David Reiss <dreiss at systemsbiology.org> wrote:
>> Hi all,
>>
>> I have a somewhat confusing question that I was wondering if someone
>> could help with. I have a pre-defined environment with some variables,
>> and I would like to define a function, such that when it is called, it
>> actually manipulates the variables in that environment, leaving them
>> to be examined later. I see from the R language definition that
>>
>> "When a function is called, a new environment (called the evaluation
>> environment) is created, whose enclosure (see Environment objects) is
>> the environment from the function closure. This new environment is
>> initially populated with the unevaluated arguments to the function; as
>> evaluation proceeds, local variables are created within it."
>>
>> So basically, I think I am asking if it is possible to pre-create my
>> own "evaluation environment" and have it retain the state that it was
>> in at the end of the function call?
>>
>> Example:
>>
>> e <- new.env()
>> e$x <- 3
>> f <- function(xx) x <- x + xx
>>
>> can I then call f(2) and have it leave e$x at 5 after the function
>> returns? I know that
>>
>> environment(f) <- e
>>
>> goes part of the way, but I would like to let the function also write
>> to the environment.
>>
>> Thanks for any advice.
>>
>> --David
>>
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>>
>