How to overload the assignment operator?

Thanks Simon,

You cannot use S3 here, because you want to dispatch on the *second*  
argument.

"<-" <- function(x, value)UseMethod("<-", value)
DOES dispatch on the second argument (see the dispatchsecond example below)

Why don't you take the external pointer approach that many others take  
to provide proxy objects to external data? (DB access, mem-mapped  
files, cross-language objects, etc.) That allows you to define your  
storage semantics very efficiently in C. You can still choose to  
define any syntactic sugar you want in either S3 or S4.

I AM using the external pointer approach and this works verly well - if one tolerates that the external data is not duplicated when the proxy object is copied. I was wondering however, if it is possible to perfectly mimic R's copying semantics: duplicate external object (and the external pointer) on assignment (or even better only on modify after assignment).

Best regards

Jens Oehlschl?gel

dispatchsecond <- function(first, second)

+ UseMethod("dispatchsecond", second)

dispatchsecond.default <- function(first, second){

+ cat("here default\n")
+ }

dispatchsecond.ff <- function(first, second){

+ cat("here ff\n")
+ }

default <- 1
ff <- 1
class(ff) <- "ff"

dispatchsecond(1,default)

here default

dispatchsecond(1,ff)

here ff

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