Not in Swift

In Swift, the "not" operator is represented by the exclamation mark (!). It is used to revert the boolean value of a condition. For example:

let isRaining = false
if !isRaining {
   print("It's not raining.")
}

In the above code, the !isRaining condition evaluates to true because isRaining is false, so the code inside the if statement is executed.

Here's another example:

let age = 20
if !(age > 18) {
   print("You are not an adult.")
}

In the above code, the !(age > 18) condition evaluates to false because age > 18 is true, so the code inside the if statement is not executed.

Basically, you use ! in Swift to negate the value of a boolean expression.