gistfile1

e = Enumerator.new { |y| (1..10).each { |v| y << v } }
# => #<Enumerator: ...>
e.count
# => 10
e.group_by { |v| v.even? }
# => {false=>[1, 3, 5, 7, 9], true=>[2, 4, 6, 8, 10]}
e.take_while { |v| v < 5 }
# => [1, 2, 3, 4]
e.to_a
# => [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
e.rewine
# => #<NoMethodError: undefined method `rewine' for #<Enumerator: #<Enumerator::Generator:0x0000010127d380>:each>>
e.rewind
# => #<Enumerator: ...>
loop { puts e.next }
# => nil