Reopening classes

animals.rb

$ ruby -v
ruby 2.3.0p0 (2015-12-25 revision 53290) [x86_64-darwin15]
$ pry
[1] pry(main)> class Animal
[1] pry(main)*   def noise
[1] pry(main)*     "bump"
[1] pry(main)*   end  
[1] pry(main)* end  
=> :noise
[2] pry(main)> class Dog < Animal
[2] pry(main)*   def noise
[2] pry(main)*     "woof"
[2] pry(main)*   end  
[2] pry(main)* end  
=> :noise
[3] pry(main)> Dog.new.noise
=> "woof"
[4] pry(main)> class Dog
[4] pry(main)*   def noise
[4] pry(main)*     "bark"
[4] pry(main)*   end  
[4] pry(main)* end  
=> :noise
[5] pry(main)> Dog.new.noise
=> "bark"
[6] pry(main)>