Basically, I see two options here:

1) Using environments

# Temp environment
env <- new.env(parent=emptyenv())
env$state1 <- list(n=100, won=0)
env$state2 <- list(n=100, won=0)

fight2 <- function(stateA, stateB, envir){
#  get(stateA, envir=envir)$n <- 50
     # The above is what you would want to do, but
     # 'get<-' is not defined, so:
     temp <- get(stateA, envir=envir)
     temp$n <- 50
     assign(stateA, value=temp, envir=envir)

     # Same for stateB
     temp <- get(stateB, envir=envir)
     temp$n <- 50
     assign(stateA, value=temp, envir=envir)

     return(TRUE)
}

fight2(stateA="state1", stateB="state2", envir=env)

# Extract from environment
state1 <- env$state1
state1
state2 <- env$state2
state2

2) Using Reference Classes

# Class Def
setRefClass("State",
     fields=list(n="numeric", won="numeric"),
     methods=list(
         fight2=function(...){
             fight2Ref(.self=.self, ...)
         }
     )
)
# Set Generic
setGeneric(name="fight2Ref", signature=".self", def=function(.self, ...)
     standardGeneric("fight2Ref"))
# Set Method
setMethod(f="fight2Ref", signature="State",
     definition=function(
         .self,
         value,
         ...
     ){
         .self$n <- value
     }
)
# Note:
# You could also put the code inside 'fight2Ref' directly inside the 
class def,
# but I don't want them to be too crowded, so I go by 'divide and conquer'

# Instantiate objects
state1 <- new("State", n=100, won=0)
state1
state2 <- new("State", n=100, won=0)
state2

# Apply method
state1$fight2(value=50)
state1
state2$fight2(value=50)
state2

# Back to list
stateToList <- function(obj, ...){
     fields <- names(getRefClass("State")$fields())
     out <- lapply(fields, function(x.field){
         obj$field(x.field)
     })
     names(out) <- fields
     return(out)
}
state1 <- stateToList(state1)
state1
state2 <- stateToList(state2)
state2

HTH,
Janko

On 06.12.2011 22:06, R. Michael Weylandt wrote:
> No pointer functionality in R (that I know of), but if you want to
> return two objects as one the standard way is to put them in a list
> and to return that list.
>
> Michael
>
> On Tue, Dec 6, 2011 at 2:35 PM, Yev<kirpich@gmail.com>  wrote:
>> I'm trying to write a function that takes several objects with many
>> different attributes and then changes their attributes. So what I wanted to
>> happen in the simplified example below is for the function to change the
>> attributes of the objects state1 and state2 that are passed to it. But
>> because stateA and stateB are local, this isn't working. Are there any easy
>> solutions?
>>
>> e.g., if I could combine the two objects stateA and stateB into a single
>> object, I could return it and then assign it back to objects state1 and
>> state2. Or if I could pass a pointer to the original object.. But I cannot
>> find an easy way of doing either.  Thanks in advance..
>>
>> state1<- list(n=100, won=0)
>> state2<- list(n=100, won=0)
>>
>> fight2<- function(stateA, stateB){
>>    stateA$n<- 50
>>    stateB$n<-50
>> }
>>
>> fight2(state1,state2)
>>
>> state1$n
>> state2$n
>>
>>         [[alternative HTML version deleted]]
>>
>> ______________________________________________
>> R-help@r-project.org  mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guidehttp://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
> ______________________________________________
> R-help@r-project.org  mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guidehttp://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>


-- 
------------------------------------------------------------------------

*Janko Thyson*
janko.thyson@ku-eichstaett.de <mailto:janko.thyson@ku-eichstaett.de>

Catholic University of Eichstätt-Ingolstadt
Ingolstadt School of Management
Statistics and Quantitative Methods
Auf der Schanz 49
D-85049 Ingolstadt

www.wfi.edu/lsqm <http://www.wfi.edu/lsqm>

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