On 12/02/2013 9:11 AM, Greg Minshall wrote:
hi. i've looked for (and not found) an assert() function. needing one,
i created the following (from stop()). i'm posting it in case 1)
someone sees a problem with this; and 2) someone else has a need.
stopifnot() might do what you want.
The tricky thing in writing this sort of function is handling vector
inputs. Sometimes x is a vector, and then you need to decide what to do
with
assert(x > 0)
Yours will only test the first component and issue a warning; the base
one will test all(x > 0). But the base behaviour causes its own
problems; one came up recently in that
stopifnot( ncol(x) > 1 )
will not stop if x is just a vector, because ncol(x) is NULL, so ncol(x)
> 1 is a length 0 vector, and all(ncol(x) > 1) is TRUE.
Duncan Murdoch
cheers, Greg
----
## an assert mechanism...
assert <- function (shouldbe, ...) {
if (!shouldbe) {
.Internal(stop(as.logical(TRUE),
.makeMessage("assertion failure: ", ..., domain = NULL)))
}
}
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