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iOS Swift 2.0 Collections and Control Flow Control Flow With Loops Working with Loops

Posted by Justus Aberson
Justus Aberson
1,035 Points

While loop question.

Hey guys, I was just wondering, why is the code im writing here not ok? Thanks.

while.swift 
let numbers = [2,8,1,16,4,3,9]
var sum = 0
var counter = 0

// Enter your code below
while counter < numbers.count {
counter++
sum = sum + (numbers[counter])
}

1 Answer

Henrik Brüntrup
Henrik Brüntrup
5,485 Points
Henrik Brüntrup
Henrik Brüntrup
5,485 Points

Hi Justus,

arrays start at 0, not at 1. So your code should look like:

let numbers = [2,8,1,16,4,3,9]
var sum = 0
var counter = 0

// Enter your code below
while counter <= (numbers.count - 1) {

    sum = sum + numbers[counter]
    counter += 1
}

Adding array positions 0 though 6. Yours was 1 through 7, throwing an out of index range since you do not have a position 7 in your array.

Best regards, Henrik

Henrik Brüntrup
Henrik Brüntrup
5,485 Points
Henrik Brüntrup
Henrik Brüntrup
5,485 Points

You might have to use

counter ++

as 

counter += 1

is Swift 3.0 syntax.

Let me know if this works!

J.D. Sandifer
J.D. Sandifer
18,813 Points
J.D. Sandifer
J.D. Sandifer
18,813 Points

Just to clarify for any folks new to programming reading this answer, flipping the order of counter++ and sum = sum + numbers[counter] was the main issue.

The comparison counter <= (numbers.count - 1) is equivalent to counter < numbers.count. However, counter++ has been deprecated as Henrik pointed out in the next answer. You should use counter += 1 instead.

And just for fun, sum = sum + numbers[counter] can be re-written as sum += numbers[counter] for more brevity.