1# The module for the Collatz conjecture needed functions
 2module RosettaCollatz
 3  VERSION = "0.1.0"
 4
 5  # Returns the collatz number of `a`
 6  #
 7  # If `a` is even, divide it by 2. Otherwise, multiply 3 by `a`, and
 8  # add 1.
 9  def self.collatz(a)
10    if a % 2 == 0
11      a // 2
12    else
13      3 * a + 1
14    end
15  end
16
17  # Returns a sequence of collatz integers starting from a.
18  def self.collatz_sequence(a)
19    result = "#{a}: "
20    i = a
21    while i >= 1
22      if i == 1
23        result = result + "1"
24        break
25      end
26      result = result + "#{i}, "
27      i = collatz(i)
28    end
29    result
30  end
31end
32
33sequence = Array.new(10000) { |i| Collatz.collatz_sequence(i + 1) }
34puts (sequence.reduce("") { |acc, i| "#{acc}\n" + "#{i}" })