Logical operators

Swift's logical NOT, AND, and OR operators are the same as most C-based languages:

let saturday = true 
let raining = false 
let christmas = true 

let b1 = !saturday // false 
let b2 = saturday && raining // false 
let b3 = saturday || raining // true 

Multiple operators are allowed, and are left-associative, that is, sub-expressions are evaluated from left to right:

let b4 = (saturday || raining) && !christmas 

In the preceding code, (saturday || raining) is evaluated first, and the result of that evaluation goes on to be evaluated with && !christmas. The parentheses as added are permissible, which can add clarity to your code, although they make no difference here to the code's outcome.