Hi R-devel. Is the following behavior in g1() and h1() expected? It seems
to make "..." arguments work slightly differently from named arguments.
#missing() has the property that it looks "up the chain"
#for example, "z" can be missing in f3 even if
#that argument did have a name ("y") in f2
f1 <- function(x, ...) {
cat("In f1, missing(x) is ", missing(x), "\n")
f2(x, ...)
}
f2 <- function(y, ...) {
cat("In f2, missing(y) is ", missing(y), "\n")
f3(y, ...)
}
f3 <- function(z, ...) {
cat("in f3, missing(z) is ", missing(z), "\n")
}
f1( , 2) #all TRUE
#does this also work with ... arguments? It seems to lose track.
g1 <- function(...) {
cat("In g1, missing(..1) is ", missing(..1), "\n")
g2(...)
}
g2 <- function(...) {
cat("In g2, missing(..1) is ", missing(..1), "\n")
g3(...)
}
g3 <- function(...) {
cat("in g3, missing(..1) is ", missing(..1), "\n")
}
g1( , 2) #TRUE, TRUE, FALSE ?!
# we can also elicit this lossiness without looking at the virtual ..n
# symbols:
h1 <- function(x, ...) {
cat("in h1, missing(x) is ", missing(x), "\n")
h2(x, ...)
}
hh1 <- function(...)
h2(...)
h2 <- function(...)
h3(...)
h3 <- function(z, ...)
cat("in h3, missing(z) is ", missing(z), "\n")
h3( , 1) #missing in h3
h2( , 1) #missing in h3
h1( , 1) #missing in h1 but NOT h3
hh1( , 1) #also not missing in h3
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