The while loop

A while loop executes a Boolean expression at the start of the loop, and the set of statements run until a condition becomes false. It is important to note that while loops can execute zero or more times. Here is the basic syntax of a while loop:

while <condition> { 
 // statement 
} 

Let's write a while loop in Playgrounds and see how it works. You have to add the following:

So, this while loop starts with a variable that begins at zero. Before the while loop executes, it checks to see whether y is less than 50, and, if so, it continues into the loop. Using the += operator, which we covered earlier, we increment y by five each time. Our while loop will continue to do this until y is no longer less than 50. Now, let's add the same while loop after the one we created and see what happens:

while y < 50 {
    y += 5
    print("y: \(y)")
}

When you are done, you should see the following:

You will notice that the second while loop never runs. This may not seem like it is essential until we look at our next type of loop.