 var teacherName = "Sheets";
 
 sayHiTeacher8(name: &teacherName, "Swift 1")
-
-print(teacherName)
 //: The above variable `teacherName`'s value was changed within the function body and now has a new value.
 /*:
  ## Return values

}
sayHiTeacher3(teacherName: "Mr. Sheets", className: "Swift")
/*:
 ### Omitting External Parameter Names
 You can omit *external* names by using the underscore `_` in front of second or subsequent parameters.
 */
func sayHiTeacher4(name: String, _ className: String) {
    
    print("Hi \(name), from my \(className) class");
}
sayHiTeacher4(name: "Mr. Sheets", "Swift")
/*:
 ### Default Parameter Values
 Function parameters can be set to a default value and omitted from a function call. It's recommended that you place all defaulted parameters at the end of the parameter list.

sayHiTeacher6(name: "Mr. Sheets", classNames: "Swift 1", "Swift 2", "Swift 3")
/*:
 ### Constant and Variable Parameters
 By default function parameters are defined as constants, meaning that you are not allowed to change the value. If you want the parameter to be a variable, you can redefine the parameter as a variable, providing you the ability to change the value and not define another variable with a different name.
 */
func sayHiTeacher7(teacherName name: String, className: String) {
    
    var name = name
