What does "==.n" mean?

[Nicholas Stowell]

Hello,

I was given .do files for a big project from my predecessor at work. I'm hoping someone can help me interpret this bit of code:

ds, has(type numeric)
foreach var of varlist `r(varlist)' {
  replace `var' = .  if `var' < 0
  replace `var' = .  if `var' == .n
}

Specifically, I do not understand what "==.n" means. I cannot find it in any search or help files. I've never seen this syntax before.

[Nick Cox]

It is a specific code for missing.

search .n

does find sources, but go straight to

help missing