[Rd] Recursion error after upgrade to R_2.11.1 [Sec=Unclassified] [Sec=Unclassified]

[Troy Robertson]

>
> On 10/06/2010 06:12 PM, Troy Robertson wrote:
> > Hi all,
> >
> > After no replies to my previous message I thought I might show some
> > code to demonstrate the change and again seek any
> explanation for the
> > error now thrown by my code after upgrading from 2.10.1 to 2.11.1.
> >
> > Thanks
> > Troy
> > --------------------------------------------------------
> > setClass("PortableObject",
> >         representation(test1    = "character"),
> >
> >         prototype(      test1   = ""),
> >           contains = ".environment"
> > )
> >
> > setMethod("initialize", "PortableObject",
> >     function(.Object, ..., .xData=new.env(parent=emptyenv())) {
> >                 .Object <- callNextMethod(.Object, ...,
> .xData=.xData)
> >
> >                 .Object at test1 <- "Foo"
> >                 # Following line works under 2.10.1 but now throws
> >                 # Error: evaluation nested too deeply:
> infinite recursion / options(expressions=)?
> >                 #####.Object[["test2"]] <- "Bar"
> >                 # The following does what I want though
> >                 .Object$test3 <- "Baa"
> >
> >                 return(.Object)
> >         }
> > )
> >
> > e <- new("PortableObject")
>
> The explicit example does help -- it's clear what bug you are
> encountering. Here's the code in R-2.10
>
> > selectMethod("[[<-", ".environment")
> Method Definition:
>
> function (x, i, j, ..., value)
> {
>     call <- sys.call()
>     call[[2]] <- x at .Data
>     eval.parent(call)
>     x
> }
>
>
> and 2.11.1
>
> > selectMethod("[[<-", ".environment")
> Method Definition:
>
> function (x, i, j, ..., value)
> {
>     .local <- function (x, i, j, ..., exact = TRUE, value)
>     {
>         call <- sys.call()
>         call[[2]] <- x at .Data
>         eval.parent(call)
>         x
>     }
>     .local(x, i, j, ..., value = value)
> }
>
> Apparently the 'exact' argument has been added, and because
> the method signature differs from the generic, a .local
> function is created. That 'sys.call()' originally returned
> the environment in which the generic was called, but now it
> returns the environment in which .local is defined. And so
> eval() keeps evaluating .local(). This I think is a bug.

Yes, afer the email from William Dunlop, I found this difference in the methods between 2.10.1 and 2.11.1
I had a play and by adding my own method to overload "[[<-" for my PortableObject was able to reinstate the original functionality without the recursive error.

setMethod("[[<-", "PortableObject",
        function (x, i, j, ..., value)
        {
                call <- sys.call()
                call[[2]] <- x at .Data
                eval.parent(call)
                x
        }
)

>
> For what it's worth, if I were interested in minimizing
> copying I would set up initialize so that it ended with
> callNextMethod(<...>), on the hopes that the method
> eventually called would take care not to make too many copies
> on slot assignment.
>
> Martin
>

Hmmm, not sure what you mean here?  My code passes objects such as these as parameters to other S4 classes which alter their data.  If the .xData slot is used then I have no need to return the object.  No copy-on-change is performed but data held by the PortableObject is modified.  This speeds up my execution time by a LARGE amount.

I could very well have things all arse-about, having come from a Java OO background, but this is the only way I have been able to create a pass-by-reference paradigm using S4 classes.  Any suggestions for alternative solutions would be greatfully received.

Troy

> >
> > alterEGo <- function(o = "EPOCObject") {
> >         o at test1 <- "Boo"
> >
> >         # Following line works under 2.10.1 but now throws
> >         # Error: evaluation nested too deeply: infinite
> recursion / options(expressions=)?
> >         ####o[["test2"]] <- "Who"
> >         # The following does what I want though
> >         o$test3 <- "Hoo"
> >
> >         # NOTE: No return
> > }
> >
> > alterEGo(e)
> > e at test1
> > e$test2
> > e[["test3"]]
> > e at .xData[["test3"]]
> >
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