Variables and types

We can declare variables as follows:

var a: Int = 1

In the preceding line of code, a is declared to be of type Int, with a value of 1. Since only an Int can be assigned the value 1, Swift can automatically infer the type of a, and it is not necessary to explicitly include the type information in the variable declaration:

var a = 1

In the preceding code, it is equally clear to both Swift and the reader what type a belongs to.

The value of a var can be changed by simply assigning to it a new value:

var a = 1 
a = 2 

However, in Swift, we can also declare a constant, which is immutable, using the...