To fully understand generics, we need to understand the problem that they are designed to solve. Let's say that we wanted to create functions that swapped the values of two variables (as described in the first part of this chapter); however, for our application, we need to swap the instances of two Integer types, two Double types, and two String types. Without generics, this would require us to write the following three functions:

func swapInts (a: inout Int, b: inout Int)  { 
    let tmp = a  
    a = b 
    b = tmp 
} 
 
func swapDoubles(a: inout Double, b: inout Double)  { 
    let tmp = a  
    a = b 
    b = tmp 
} 
 
func swapStrings(a: inout String, b: inout String)  { 
    let tmp = a  
    a = b 
    b = tmp 
}  

With these three functions, we can swap the instances of two Integer types, two Double types, and two String types. Now, let's say...