func quicksort[arr: Array] : Void
    do_quicksort(arr, 0, Array.size(arr)-1)

func do_quicksort[arr: Array, low: I64, high: I64] : Void
    if low < high
        let i: I64 = partition(arr, low, high)
        do_quicksort(arr, low, i - 1)
        do_quicksort(arr, i + 1, high)

func partition[arr: Array, low: I64, high: I64] : I64
    let pivot: I64 = arr[high]
    let i: I64 = low - 1
    for j in (low)..high
        if arr[j] <= pivot
            i = i + 1
            let temp: I64 = arr[i]
            Array.set(arr, i, arr[j])
            Array.set(arr, j, temp)
    let temp: I64 = arr[i + 1]
    Array.set(arr, i + 1, arr[high])
    Array.set(arr, high, temp)
    return i + 1

func main[] : I64
    let arr: Array = []
    for i in 0..10
        Array.push(arr, Math.abs(Math.urandom() % 1000))

    for i in 0..Array.size(arr)
        print_i64(arr[i])
    print("------------")

    quicksort(arr)

    for i in 0..Array.size(arr)
        print_i64(arr[i])