SelectionSort.swift

// Using XCode 7.3.1 (it's all I had at the time)

extension MutableCollectionType where Generator.Element == SubSequence.Generator.Element {
    mutating func selectionSort(isOrderedBefore compare: (Generator.Element, Generator.Element) throws -> Bool) rethrows {
        for currentIndex in self.startIndex ..< self.endIndex {
            // (index,element) pairs after the current index
            let pairs = zip(currentIndex ..< self.endIndex, self.suffixFrom(currentIndex)).lazy
            
            // the pair with the minimum element
            let pair = try pairs.minElement({ try compare($0.1, $1.1) })
            
            // swap the pair, should never be nil but checking anyway
            if let (minIndex, minElement) = pair {
                self[minIndex] = self[currentIndex]
                self[currentIndex] = minElement
            }
        }
    }
}

extension MutableCollectionType where Generator.Element == SubSequence.Generator.Element, Generator.Element: Comparable {
    mutating func selectionSort() {
        return self.selectionSort(isOrderedBefore: <)
    }
}