I'm trying to do an XOR operation in Swift 5. The documentation does not seem to mention explicitly doing it with two boolean values here:

<https://docs.swift.org/swift-book/LanguageGuide/AdvancedOperators.html>

Is this possible? It says to use the `^` operation but I get the error when trying: 

```
 card != nil ^ appointment.instructor == nil

```

> 
> ERROR Adjacent operators are in non-associative precedence group 'ComparisonPrecedence' 
> 
> 
>