iter.rb

# Ruby iteration

range = (1..100)

# internal iteration
range.each { |i| puts i } #=> 1, 2, 3, 4, ..

# external iteration
it = range.to_enum
it.next #=> 1
it.next #=> 2

# generator object (lazily generating values)
g = Enumerator.new { |y| 
  v = 0
  while true 
    y.yield v += 2 
  end 
}

g.next #=> 2
g.next #=> 4