And it doesn't even select "the first method lexicographically in the
ordering" (whatever that means):
setClass("B", "NULL")
setClass("A", "NULL")
setMethod("show", "B", function(object) cat("B object\n"))
setMethod("show", "A", function(object) cat("A object\n"))
setClass("AB", contai
Hi Zehnder,
You're right that the fact that B already inherits from A is probably
part of the story but it's not all the story:
setClass("A", "NULL")
setClass("B", "A")
setMethod("show", "A", function(object) cat("A object\n"))
setMethod("show", "B", function(object) cat("B object\n"))
On Wed, Aug 14, 2013 at 11:36 AM, Simon Zehnder wrote:
> Because the signature is always (A,A) or (B,B). Then, as in AB we have A and
> B and no relationship between A and B, R chooses the method
> lexicographically. The result is as expected: f for A is chosen.
It's not as expected, because it
Because the signature is always (A,A) or (B,B). Then, as in AB we have A and B
and no relationship between A and B, R chooses the method lexicographically.
The result is as expected: f for A is chosen.
If you would do something like:
setClass("A", contains = "list")
setClass("B", contains = "
> In my opinion the reason for the behavior lies in the specific multiple
> inheritance structure between AB, B and A.
So what if we don't make such a weird inheritance structure, and
instead have A and B inherit from a common parent:
setClass("A", contains = "list")
setClass("B", contains = "li
Ambiguity is indeed detected by R and the user is informed on it. But in the
case of Hadley's example, I still believe, that the specific multiple
inheritance structure creates this behavior. If you call:
showMethods("f")
Function: f (package .GlobalEnv)
x="A", y="A"
x="AB", y="AB"
(inherite
Hi Hadley,
I suspect that the dispatch algorithm doesn't realize that selection
is ambiguous in your example. For 2 reasons:
(1) When it does realize it, it notifies the user:
setClass("A", "NULL")
setGeneric("f", function(x, y) standardGeneric("f"))
setMethod("f", sig
If you take an example which works with slots,
setClass("A", representation(a = "numeric")
setClass("B", contains = c("A"), representation(b = "numeric"))
a <- new("A", a = 2)
b <- new("B", a = 3, b = 2)
setClass("AB", contains = c("A", "B"))
new("AB", a = 2, b = 3)
You see, that there is only o
> The class AB inherits from A and from B, but B already inherits from class A.
> So actually you only have an object of class B in your object of class AB.
> When you call the function f R looks for a method f for AB objects. It does
> not find such a method and looks for a method of the object
Hadley,
The class AB inherits from A and from B, but B already inherits from class A.
So actually you only have an object of class B in your object of class AB. When
you call the function f R looks for a method f for AB objects. It does not find
such a method and looks for a method of the objec
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