Omitting argument labels

All of the functions in this chapter have used labels when passing arguments into the functions. If we do not want to use a label, we can omit it by using an underscore. The following example illustrates this:

func sayHello(_ name: String, greeting: String) {  
  print("\(greeting) \(name)") 
}

Notice the underscore prior to the name label in the parameter list. This indicates that the name label should not be used when calling this function. Now, we are able to call this function without using the name label:

sayHello("Jon", greeting: "Hi") 

This call would print out Hi Jon.