= userName ?? "Guest" func sum(number1 a:Int, number2 b:Int) -> Int { return a + b } fruits.sort({ (s1: String, s2: String) -> Bool in return s1 < s2 }) func say(greet: String) -> (String -> String) { func greet(name: String) -> String { return "\(greet), \(name)!" } return greet }