[Rd] how to add method to .Primitive function

[Gabor Grothendieck]

On 5/7/05, Vadim Ogranovich <vograno at evafunds.com> wrote:
> I tried to write the dim method for the list class, but R doesn't seem
> to dispatch to it:
> > dim.list = function(x) c(length(x[[1]]), length(x))
> > dim(list(1))
> NULL
> > dim.list(list(1))
> [1] 1 1
> 
> What is the correct way of registering dim.list with .Primitive("dim")?

The list method of dim is sealed 

> isSealedMethod("dim", "list")
[1] TRUE

but you could define a subclass, mylist, and use that:

> setClass("mylist", representation(x = "list"), contains = "list")
[1] "mylist"
> setMethod("dim", "mylist", function(x) c(length(x at x[[1]]), length(x at x)))
[1] "dim"
> x <- new("mylist", x = list(x = 1, y = 2))
> dim(x)
[1] 1 2