Booleans

In Swift, Booleans are capitalized:

let myBool: Bool = true 

It will not surprise you to learn that Boolean values come in two flavors: true and false.

However, that really is all you get; true doesn't equal 1, and false doesn't mean nil, or 0, or anything else but false:

let myBool = false 
myBool == nil // no it doesn't 
myBool == 0   // error 

The second line evaluates to false, because myBool does have a value and so will not be equivalent to nil (whether its value is true or false). You'll see shortly that Swift is very choosy about how it handles the concept of nil (see the Optionals section of this chapter).

The third line will not even compile--you'll get an error informing you that you can't compare a Bool with an Int. In Swift, you can have 0 teeth, but you can't have false teeth.