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\name{reg.finalizer}
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\name{reg.finalizer}
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\alias{reg.finalizer}
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\alias{reg.finalizer}
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\title{Finalization of objects}
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\title{Finalization of objects}
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\description{
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\description{
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  Registers an \R{} function to be called upon garbage collection of object.
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  Registers an \R function to be called upon garbage collection of
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  object.
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}
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}
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\usage{
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\usage{
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  reg.finalizer(e, f)
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  reg.finalizer(e, f)
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}
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}
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\arguments{
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\arguments{
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  \item{e}{Object to finalize. Must be environment or external pointer.}
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  \item{e}{Object to finalize. Must be environment or external pointer.}
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  \item{f}{Function to call on finalization. Must accept a single argument,
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  \item{f}{Function to call on finalization. Must accept a single argument,
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     which will be the object to finalize.}
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    which will be the object to finalize.}
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}
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}
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\value{
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\value{
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  \code{NULL}.
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  \code{NULL}.
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}
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}
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\note{
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\note{The purpose of this function is mainly to allow objects that
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  The purpose of this function is mainly to allow objects that refer to
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   refer to external items (a temporary file, say)
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  external items (a temporary file, say) to perform cleanup actions when
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   to perform cleanup actions when they are no
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   longer referenced from within \R{}. This only makes sense for objects
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  they are no longer referenced from within \R.  This only makes sense
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   that are never copied on assignment, hence the restriction to environments
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  for objects that are never copied on assignment, hence the restriction
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   and external pointers.}
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  to environments and external pointers.
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}
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\examples{
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\examples{
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f <- function(e) print("cleaning....")
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f <- function(e) print("cleaning....")
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g <- function(x){e<-environment(); reg.finalizer(e,f)}
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g <- function(x){e<-environment(); reg.finalizer(e,f)}
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g()
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g()
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invisible(gc()) # trigger cleanup
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invisible(gc()) # trigger cleanup