问如何测试条件在R中返回数字(0)的情况

EN

isEmpty <- function(x) {
    return(length(x)==0)
}

input <- c(3, 12);

if (!isEmpty(setdiff(input, 1:9))) {
    stop ("not valid")
}

isEmpty <- function(x) {
    return(identical(x, numeric(0)))
}

input <- c(3, 12)

if (!isEmpty(setdiff(input, 1:9))) {
    stop ("not valid")
}

# 1. Check if 'integer(0)'
is.integer0 <- function(x) {
  is.integer(x) && length(x) == 0L
}

# 2. Check if 'numeric(0)'
is.numeric0 <- function(x) {
  identical(x, numeric(0))
}

# 3. Check is 'integer0' or 'numeric0'
is.int_num_0 <- function(x) {
  is.integer0(x) || is.numeric0(x)
}