Result sorting example Swift not showing up in Playground

Question

I'm trying to work out an example which is provided on developer.apple.com website 'Swift Playground'. I had to adapt it a little since swift 2 is, what looks like, different in handling 'inout' variables. In the example showed on the presentation 'inout' was not used in the function declaration. Anyway the result of 'data' is not showing in the Playground although the code doesn't show any compile errors.

import UIKit

var data = [16, 97, 13, 55, 95, 53, 18, 10, 79, 53, 79, 34, 50, 34, 0, 91, 94, 55, 6, 38, 7]

func exchange<T>(inout data:[T], i: Int, j: Int) {
    let temp = data[i]
    data[i] = data[j]
    data[j] = temp
}

func swapLeft<T: Comparable>(inout data: [T], index: Int) {
    for i in reverse(1...index) {
        if data[i] < data[i-1] {
            exchange(&data, i, i-1)
        }else {
            break
        }
    }
}

func isort<T: Comparable>(inout data: [T]) {
    for i in 1...data.count {
        swapLeft(&data,i)
    }
}
data //result [16, 97, 13, 55, 95, 53, 18, 10, 79, 53, 79, 34, 50, 34, 0, 91, 94, 55, 6, 38, 7]
isort(&data)
data //no result shown

Screenshot

I think you got the correct answer now, but as an additional hint: You could have found the error yourself in the "Assistant Editor" (View -> Assistant Editor -> Show Assistant Editor). Also, if anything goes wrong in the Playground, I can only recommend to test the code in a compiled project (better error messages, better debugging possibilities). — Martin R, Aug 13 '15 at 10:56

score 2 · Accepted Answer · answered Aug 13 '15 at 10:51

2

It isn't showing a result because it is crashing with Array index out of range. Try this for isort:

func isort<T: Comparable>(inout data: [T]) {
    for i in 1..<data.count {
        swapLeft(&data,i)
    }
}

answered Aug 13 '15 at 10:51

vacawama

150,663
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@OlivierdeJonge: Unless you are using an ancient Xcode version, it should be `1 ..< data.count`, exactly as in this answer. – Martin R Aug 13 '15 at 11:23
The half-open range operator was changed from `..` to `..<` on 7 July 2014 according to the Swift iBook. It was Xcode 6.0 beta 3. Very ancient. – vacawama Aug 13 '15 at 12:19
Thanks to you all my problem was a typo .. instead of .. – Olivier de Jonge Aug 13 '15 at 12:20

score 1 · Answer 2 · edited May 23 '17 at 10:31

1

You can always use println(data)

Make sure your Debug Area is shown. See this post for more info.

edited May 23 '17 at 10:31

Community

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answered Aug 13 '15 at 09:53

Roland Keesom

8,180
5
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added screenshot, println doesn't help – Olivier de Jonge Aug 13 '15 at 10:03

Result sorting example Swift not showing up in Playground

2 Answers2