NULL objects.
null() as.null(x) is.null(x)
null and
as.null always return
NULL.
is.null returns
TRUE or
FALSE,
according as
x is or is not
NULL.
Both
is.null and
as.null are generic; currently there are
no methods defined for either of them.
An object can be of length
0 and not be
NULL, see the examples section.
is.null(character(0)) # returns FALSE