And also:
> mapply(paste, c(a="A"), character(), USE.NAMES = TRUE)
Error in names(answer) <- names1 :
'names' attribute [1] must be the same length as the vector [0]
When the shortest arguments get recycled to the length of the longest,
shouldn't their names also get recycled?
> mapply(paste, c(a="A", b="B"), letters[1:6], USE.NAMES=TRUE)
a b
"A a" "B b" "A c" "B d" "A e" "B f"
That's assuming that rep() accurately materializes recycling (I hope it
does):
> rep(c(a="A", b="B"), length.out=6)
a b a b a b
"A" "B" "A" "B" "A" "B"
> rep(c(a="A", b="B"), length.out=0)
named character(0)
I always wished that the process of recycling which happens everywhere
all the time in R was implemented in its own dedicated function
recycle(). But that's another story.
Anyways, back to mapply(): Once what happens to the names during
recycling is clarified, there should be no need to be explicit about
what should happen when the length "of the first ... argument" is zero
because it will no longer be a special case.
Cheers,
H.
On 30/11/2021 22:10, Henrik Bengtsson wrote:
Hi,
in R-devel (4.2.0), we now get:
mapply(paste, "A", character(), USE.NAMES = TRUE)
named list()
Now, in ?mapply we have:
USE.NAMES: logical; use the names of the first ... argument, or if
that is an unnamed character vector, use that vector as the names.
This basically says we should get:
answer <- list()
first <- "A"
names(answer) <- first
which obviously is an error. The help is not explicit what should
happen when the length "of the first ... argument" is zero, but the
above behavior effectively does something like:
answer <- list()
first <- "A"
names(answer) <- first[seq_along(answer)]
answer
named list()
Is there a need for the docs to be updated, or should the result be an
unnamed empty list?
/Henrik
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