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

[Troy Robertson]

> -----Original Message-----
> From: Martin Maechler [mailto:maechler at stat.math.ethz.ch]
> Sent: Thursday, 7 October 2010 9:50 PM
> To: Troy Robertson
> Cc: 'Martin Morgan'; 'r-devel at R-project.org'; 'John Chambers'
> Subject: Re: [Rd] Recursion error after upgrade to R_2.11.1
> [Sec=Unclassified] [Sec=Unclassified]
>
>
> >>>>> "TR" == Troy Robertson <Troy.Robertson at aad.gov.au>
> >>>>>     on Thu, 7 Oct 2010 13:50:49 +1100 writes:
>
>     >>
>     >> 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.
>
>     TR> Yes, afer the email from William Dunlop, I found this
> difference in the methods between 2.10.1 and 2.11.1
>     TR> 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.
>
>     TR> setMethod("[[<-", "PortableObject",
>     TR> function (x, i, j, ..., value)
>     TR> {
>     TR> call <- sys.call()
>     TR> call[[2]] <- x at .Data
>     TR> eval.parent(call)
>     TR> x
>     TR> }
>     TR> )
>
>     >>
>     >> 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
>     >>
>
>     TR> 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.
>
>     TR> 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.
>
>     TR> Troy
>
> R 2.12.2 (currently beta) has in its NEWS :
>
>     o A facility for defining reference-based S4 classes (in the OOP
>       style of Java, C++, etc.) has been added experimentally to
>       package methods; see ?ReferenceClasses.
>
> ---> Please get R-2.12.2 beta and tell here about your
> experiences. John Chambers (you have in CC) will be
> particularly interested in your feedback.
>
> Martin Maechler, ETH Zurich
>
>

Well...

Just been having a read of the doco for the new reference classes.
This opens up a whole new world in R doesn't it.  Very exciting.
Except for the fact that it negates a lot of what I have been doing on top of S4 objects.  I will probably now be rewritting a lot of code.  Ouch!

I'll start having a bit of a play and exploring this new way of doing things and let you know how I go.
Will probably have questions along the way too.

Thank you to everyone involved for their hard work.

Troy
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