Existence of formal arguments.
Note the difference between
test <- function(a) {
exists("a", mode = "symbol")
}
test()
and
test2 <- function(a) {
exists("a", mode = "numeric") #say
}
test2()
and then note that the default mode argument to exists is "any".
Rolf Turner wrote:
I just discovered what seems to me to be a slight funny in respect
of formal argument names. If I define a function
foo <- function(a,b){ ... whatever ...}
then ``inside'' foo() the exists() function will return TRUE
from ``exists("a") whether an object named ``a'' exists or not.
But get("a") will yield an error ``object "a" not found''
in these circumstances.
I presume there is a reason for specifying that an object named
by a formal argument always exists --- but it is mysterious by my
standards. Can anyone explain the reason for this behaviour?
This is just idle curiosity --- or my hunger for knowledge, whichever
way you want to look at it :-) --- it doesn't really matter.
cheers,
Rolf Turner
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