Hi,
there seems to be a possible bug in callNextMethod in conjunction with
the [-operator.
Relevant info, minimal example and sessionInfo follow below:
###
setClass("foo", representation = representation(a = "numeric"))
setClass("bar", contains = "foo")
setMethod(
f = "[",
signature = signature("foo"),
def = function(x,i,j,...,drop=TRUE) {
cat("drop in foo-[ :", drop, "\n")
return(1)
}
)
setMethod(
f = "[",
signature = signature("bar"),
def = function(x,i,j,...,drop=TRUE) {
cat("drop in bar-[ :", drop, "\n")
# we lose the value of drop here, when the call gets
dispatched to the super method by callNextMethod
callNextMethod()
}
)
x <- new("foo")
x[1, drop=FALSE]
# drop in foo-[ : FALSE
y <- new("bar")
y[1, drop=FALSE]
# drop in bar-[ : FALSE
# drop in foo-[ : TRUE
###
#?callNextMethod
#The statement that the method is called with the current arguments is
more precisely as follows. Arguments that were missing in the current
call are still missing (remember that "missing" is a valid class in a
method signature). For a formal argument, say x, that appears in the
original call, there is a corresponding argument in the next method call
equivalent to x = x. In effect, this means that the next method sees the
same actual arguments, but arguments are evaluated only once.
###
#S3 gets this right:
'[.foo' <- function(x, i, j, ..., drop=TRUE) {
cat("drop in foo-[ :", drop, "\n")
}
'[.bar' <- function(x, i, j, ..., drop=TRUE) {
cat("drop in bar-[ :", drop, "\n")
NextMethod()
}
x <- 1
class(x) <- c("bar", "foo")
x[1, drop=FALSE]
# drop in bar-[ : FALSE
# drop in foo-[ : FALSE
###
> sessionInfo()
R version 2.11.0 Under development (unstable) (2010-01-12 r50970)
i386-pc-mingw32
locale:
[1] LC_COLLATE=German_Germany.1252 LC_CTYPE=German_Germany.1252
[3] LC_MONETARY=German_Germany.1252 LC_NUMERIC=C
[5] LC_TIME=German_Germany.1252
attached base packages:
[1] stats graphics grDevices utils datasets methods base
loaded via a namespace (and not attached):
[1] tools_2.11.0
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