Oh that's interesting... there is an if() function in the documentation, but it doesn't show up in the math functions list. @mark2atsafe I think this might be a bug. I can't get it to work so I'm wondering if it's maybe not implemented fully.
You can use Conditional Values to achieve the same thing as the if() function does, hope that helps.
I'll check with the developers, but my guess is that this no longer works. Or it works in a completely different way from what we expect. In fact, I'm not sure where it comes from since there is no IF operator in C arithmetic. But as others have said, the ternary operator (A ? B : C) works absolutely fine.