I think the inspection of the "stopifnot()" source code may help.
> stopifnot
function (...)
{
n <- length(ll <- list(...))
if (n == 0L)
return(invisible())
mc <- match.call()
for (i in 1L:n) if (!(is.logical(r <- ll[[i]]) && !anyNA(r) &&
all(r))) {
ch <- deparse(mc[[i + 1]], width.cutoff = 60L)
if (length(ch) > 1L)
ch <- paste(ch[1L], "....")
stop(sprintf(ngettext(length(r), "%s is not TRUE", "%s are not all
TRUE"),
ch), call. = FALSE, domain = NA)
}
invisible()
}
The following code may help in understanding.
(arg <- (logical(0) == 1))
(arg <- (logical(0) == TRUE))
(arg <- (logical(0) == FALSE))
n <- length(ll <- list(arg))
n
if (n == 0L)
return(invisible())
for (i in 1L:n) {
print(is.logical(r <- ll[[i]]))
print(!anyNA(r))
print(all(r))
if (! (is.logical(r <- ll[[i]]) && !anyNA(r) && all(r)) ) {
print("stop")
}
}
Executing such code:
> (arg <- (logical(0) == 1))
logical(0)
> (arg <- (logical(0) == TRUE))
logical(0)
> (arg <- (logical(0) == FALSE))
logical(0)
>
> n <- length(ll <- list(arg))
> n
[1] 1
>
> if (n == 0L)
+ return(invisible())
>
> for (i in 1L:n) {
+ print(is.logical(r <- ll[[i]]))
+ print(!anyNA(r))
+ print(all(r))
+ if (! (is.logical(r <- ll[[i]]) && !anyNA(r) && all(r)) ) {
+ print("stop")
+ }
+ }
[1] TRUE
[1] TRUE
[1] TRUE
>
See also help(all) and what its "Note" states about all(logical(0))
and consider that:
> is.logical(logical(0))
[1] TRUE
--
GG
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