Enumerators and Enumerables

gistfile1.rb

# Iterator methods without blocks are called Enumerators
[1,2,3].each_index # => #<Enumerator: [1, 2, 3]:each_index>
0.upto(10) # => #<Enumerator: 0:upto(10)>

# You can call any Enumerable method on Enumerators
[1,2,3].each_index.map {|i| i + 10 } # => [10, 11, 12]
0.upto(10).map {|i| i + 10 } # => [10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20]

# See documentation about Enumerables
# http://ruby-doc.org/core-2.1.5/Enumerable.html