var hailstone = Fn.new { |n|
    if (n < 1) Fiber.abort("Parameter must be a positive integer.")
    var h = [n]
    while (n != 1) {
        n = (n%2 == 0) ? (n/2).floor : 3*n + 1
        h.add(n)
    }
    return h
}

var h = hailstone.call(27)
System.print("For the Hailstone sequence starting with n = 27:")
System.print("   Number of elements  = %(h.count)")
System.print("   First four elements = %(h[0..3])")
System.print("   Final four elements = %(h[-4..-1])")

System.print("\nThe Hailstone sequence for n < 100,000 with the longest length is:")
var longest = 0
var longlen = 0
for (n in 1..99999) {
    var h = hailstone.call(n)
    var c = h.count
    if (c > longlen) {
        longest = n
        longlen = c
    }
}
System.print("   Longest = %(longest)")
System.print("   Length  = %(longlen)")