quicksort.ceylon

Element[] quicksort<Element>({Element*} elements)
    given Element satisfies Comparable<Element> =>
        if (exists first = elements.first)
            then [first.largerThan, first.notLargerThan]
                .map(compose(quicksort<Element>, elements.rest.filter))
                .interpose([first])
                .reduce(concatenate<Element>)
            else [];