array_inplace.swift

extension Collection {
    
    public subscript(inplace_slice bounds: Range<Index>) -> Slice<Self> {
        get { fatalError() }
        _modify {
            var slice = Slice(base: self, bounds: bounds)
            yield &slice
        }
    }
}

extension RangeReplaceableCollection where Self: MutableCollection {
    
    public subscript(inplace_native bounds: Range<Self.Index>) -> Self.SubSequence {
        get { fatalError() }
        _modify {
            yield &self[bounds]
        }
    }
}

import Foundation

enum Operation: String {
    case sort = "Append"
    case append = "Sort"
    case removeAll = "RemoveAll"
}
let op         = Operation.removeAll
let iterations = 1000


var randomArrays = [[Int]]()
func reset() {
    randomArrays.removeAll()
    for _ in 0..<iterations {
        var testArray = [Int]()
        for _ in 0..<10_000 {
            testArray.append(Int.random(in: 0 ... .max))
        }
        randomArrays.append(testArray)
    }
}

reset()

let start_norm = CFAbsoluteTimeGetCurrent()
for i in 0..<iterations {
    switch op { // This should get optimised away.
    case .sort:
        randomArrays[i][0..<5000].sort()
    case .append:
        randomArrays[i][0..<5000].append(42)
    case .removeAll:
        randomArrays[i][0..<5000].removeAll()
    }
}
let end_norm  = CFAbsoluteTimeGetCurrent()
let time_norm = (end_norm - start_norm) / Double(iterations)

reset()

let start_slice = CFAbsoluteTimeGetCurrent()
for i in 0..<iterations {
    switch op {
    case .sort:
        randomArrays[i][inplace_slice: 0..<5000].sort()
    case .append:
        randomArrays[i][inplace_slice: 0..<5000].append(42)
    case .removeAll:
        randomArrays[i][inplace_slice: 0..<5000].removeAll()
    }
}
let end_slice  = CFAbsoluteTimeGetCurrent()
let time_slice = (end_slice - start_slice) / Double(iterations)

reset()

let start_array = CFAbsoluteTimeGetCurrent()
for i in 0..<iterations {
    switch op {
    case .sort:
        randomArrays[i][inplace_native: 0..<5000].sort()
    case .append:
        randomArrays[i][inplace_native: 0..<5000].append(42)
    case .removeAll:
        randomArrays[i][inplace_native: 0..<5000].removeAll()
    }
}
let end_array  = CFAbsoluteTimeGetCurrent()
let time_array = (end_array - start_array) / Double(iterations)

print("""
Test Results (\(op.rawValue)):
Iterations: \(iterations)

Regular subscript:       \(time_norm * 1000) ms
modify generic Slice<T>: \(time_slice * 1000) ms
modify native SubSeq:    \(time_array * 1000) ms
""")