[R] S4 method dispatch matrixOrArray

[Gabor Grothendieck]

This is surprising.  I would have thought that the parent/child relationships
determine the order that dispatched methods are invoked, not the order
that the setMethod commands are issued in.

On 4/12/06, Paul Roebuck <roebuck at mdanderson.org> wrote:
> On Wed, 12 Apr 2006, Gabor Grothendieck wrote:
>
> > On 4/12/06, Paul Roebuck <roebuck at mdanderson.org> wrote:
> >
> > > I have some code where the primary dispatching is on
> > > other parameters so I'd like not to have to create a
> > > set of functions for "matrix" and another duplicate
> > > set for "array". But the class union technique isn't
> > > working as implemented below and I don't have my Green
> > > book with me. How do I fix my infinite recursion problem?
> > >
> > >
> > > ##--------------------------------------------------------
> > > library(methods)
> > >
> > > setGeneric("foo",
> > >           function(A, ...) {
> > >               cat("generic", match.call()[[1]], "\n")
> > >               standardGeneric("foo")
> > >           })
> > >
> > > setMethod("foo",
> > >          signature(A = "vector"),
> > >          function(A, ...) {
> > >              callGeneric(matrix(A, nrow = 1), ...)
> > >          })
> > >
> > > setClassUnion("matrixOrArray", c("matrix", "array"))
> > >
> > > setMethod("foo",
> > >          signature(A = "matrixOrArray"),
> > >          function(A, ...) {
> > >              cat("A =", A, "\n")
> > >          })
> > >
> > > ## Test
> > > foo(1:4)
> > > foo(matrix(1:4, 1, 4))
> > > foo(array(1:4, c(1, 4, 1)))
> >
> > I think its good enough to just define an array method, i.e. you
> > don't need the matrix method or the matrixOrArray class, and the
> > vector method can call foo(matrix(A,1), ...) so:
> >
> > setGeneric("foo",
> >           function(A, ...) {
> >               cat("generic", match.call()[[1]], "\n")
> >               standardGeneric("foo")
> >           })
> >
> > setMethod("foo",
> >          signature(A = "array"),
> >          function(A, ...) {
> >              cat("A =", A, "\n")
> >          })
> >
> > setMethod("foo",
> >          signature(A = "vector"),
> >          function(A, ...) {
> >              foo(matrix(A, nrow = 1), ...)
> >          })
>
> Something didn't seem right here. That was pretty close
> to what I had started with, before trying to go the
> classUnion route. Matter of fact, the vector method can
> retain use of callGeneric.
>
> The solution has to do with the order in which calls to
> setMethod are made. Adding foo-vector after foo-array
> works fine; the other way around causes infinite recursion.
>
> ----------------------------------------------------------
> SIGSIG -- signature too long (core dumped)
>
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
>