quick = cluster [T: type] is select
        where T has lt: proctype (T,T) returns (bool)
    aT = array[T]
    sT = sequence[T]
    rep = null

    swap = proc (list: aT, a, b: int)
        temp: T := list[a]
        list[a] := list[b]
        list[b] := temp
    end swap

    partition = proc (list: aT, left, right, pivotIndex: int) returns (int)
        pivotValue: T := list[pivotIndex]
        swap(list, pivotIndex, right)
        storeIndex: int := left
        for i: int in int$from_to(left, right-1) do
            if list[i] < pivotValue then
                swap(list, storeIndex, i)
                storeIndex := storeIndex + 1
            end
        end
        swap(list, right, storeIndex)
        return(storeIndex)
    end partition

    _select = proc (list: aT, left, right, k: int) returns (T)
        if left = right then
            return(list[left])
        end

        pivotIndex: int := left + (right - left + 1) / 2
        pivotIndex := partition(list, left, right, pivotIndex)
        if k = pivotIndex then
            return(list[k])
        elseif k < pivotIndex then
            return(_select(list, left, pivotIndex-1, k))
        else
            return(_select(list, pivotIndex + 1, right, k))
        end
    end _select

    select = proc (list: sT, k: int) returns (T)
        return(_select(sT$s2a(list), 1, sT$size(list), k))
    end select
end quick

start_up = proc ()
    po: stream := stream$primary_output()
    vec: sequence[int] := sequence[int]$[9,8,7,6,5,0,1,2,3,4]

    for k: int in int$from_to(1, 10) do
        item: int := quick[int]$select(vec, k)
        stream$putl(po, int$unparse(k) || ": " || int$unparse(item))
    end
end start_up