[swift-users] Simplify chained calls

[Dan Loewenherz]

I’m not sure if you wanted to stick with the pure functional approach, but
here’s an alternative that uses Range<Int> to take care of most of the work.

func selectionSort(_ array: [Int]) -> [Int] {
    guard let minValue = array.min(), let index = array.index(of: minValue)
else {
        return []
    }

    let ranges = [0..<index, index.advanced(by: 1)..<array.endIndex]
    return [minValue] + selectionSort(ranges.flatMap { array[$0] })
}


On Tue, Jun 28, 2016 at 7:20 PM, Aaron Bohannon via swift-users <
swift-users at swift.org> wrote:

> I think that's about as simple as you can make it unless you allow
> yourself to remove more than one element at a time when the minimum appears
> more than once.
>
> Here's the question I find interesting: what's the simplest way to change
> that code into a version based on lazy collections?  After all, there would
> arguably be some real practical value to a lazy recursive selection sort in
> cases where only a relatively small prefix of the resulting collection was
> expected to be needed.  I took a stab at making your code lazy but quickly
> realized that it wasn't going to be as easy as I thought.
>
>
>
> On Tue, Jun 28, 2016 at 8:50 AM, Adriano Ferreira via swift-users <
> swift-users at swift.org> wrote:
>
>> Hi everyone!
>>
>> I’m experimenting with this functional selection sort code and I wonder
>> if anyone could help me simplify the portion indicated below.
>>
>>
>> // Swift 3
>>
>> func selectionSort(_ array: [Int]) -> [Int] {
>>
>>     guard array.count > 1, let minElement = array.min() else {
>>         return array
>>     }
>>
>>     let indexOfMinElement = array.index(of: minElement)!
>>
>>     // All of this just to filter out the first smallest element and
>> return the rest
>>     // Also tried ‘suffix(from:)' here, but couldn’t make it work
>> properly
>>     let rest = array.enumerated()
>>                     .filter({ index, _ in index != indexOfMinElement })
>>                     .map({ _, element in element })
>>
>>     return [minElement] + selectionSort(rest)
>> }
>>
>>
>> By the way, it feels really weird to chain method calls like this in
>> Swift 3, particularly due to the mixing of terms of art (e.g. “filter” and
>> “map”) with other methods that follow the -ed/-ing rules from the API
>> guidelines (e.g. enumerated).
>>
>> Best,
>>
>> — A
>>
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>>
>>
>
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