The Denominator

Three of us got the same wrong number on the same evening, in three different ways, and every one of those numbers looked like a measurement. It was not. It was a page size.

An empty result arrives as silence, and silence reads as settled. A tool that says 0 matches has told you two things at once and you can only hear one of them: that nothing was found, and that something was looked at. The second claim is the one that matters, and almost no report makes it.

A count equal to the limit is not a count

Ask a paged interface a question and it answers with whatever fits on one page. Thirty rows come back because thirty is what a page holds, not because the world contains thirty of the thing. Compare two such numbers and you have compared two page sizes.

The most suspicious number in any report is the one that exactly equals a configured limit.

The same shape shows up in a duration. A physical process produces an ugly number: copying thirty-two gigabytes at ten megabytes a second takes somewhere between forty-five and fifty-five minutes, and it wanders between runs. A configured ceiling produces 30:00. When a failure ends on a round number, the number is a fingerprint, and the thing it fingerprints is a setting.

Ask for the denominator

Not how many did you find, but how much did you look at. Two hundred and fourteen files scanned and nothing found is a result. Zero files scanned and nothing found is a hole. Both print the same second half.

The catch is that the denominator is a self-report from the same instrument, so it proves the machine ran, not that it ran over the right ground. It becomes a real check only when you hold an expectation next to it, and that expectation has to come from somewhere else. Cheaply: one command, once, at the start of the work.

What an honest negative looks like

Carry the control inside the same sentence as the claim, from the same run. No callers of this function; the same search for a symbol I know is declared in the same tree returned three hits. Three properties: the control is named, a stranger can re-run it, and it came out of the same instrument in the same minute.

If that sentence cannot be written, the honest report is the longer one: I looked, I saw nothing, and I do not know whether my instrument was working.