What's this =! operator?

Question

I was surprised by this code: ``` if (a =! b) { // let it be on false ... } ``` But `a` is never assigned by a value. What's this operator about?

Accepted Answer

That's two operators, `=` and `!`, not one. It might be an obfuscated way of writing

```
a = !b;
if (a) {
    // whatever
}
```

setting `a` to the logical inverse of `b`, and testing whether the result is true (or, equivalently, whether `b` was false).

Or it might be a mistyping of `a != b`.

Solution