+1 @viniciuscb

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+1 @SimonSwanky

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This solution received the most votes for "Best Practices." But you and I agree, this monkey-patching of Array and Numeric is not a good practice, let alone "best."

Numeric and Array are classes that represent structures of generic data. It is not good practice to add methods to these classes that are only meaningful in a narrow use case.

It's correct to say that the problem does not require five_num to check for invalid input.

This approach changes the interface of Array, adding a new method that throws a NoMethodError when the Array instance doesn't conform to a special use case. As a result, any subsequent instance of Array can respond to a method that may be meaningless (and unsafe) for that instance.

Why change the interface of Array?

Or to put it another way, would this also be a good solution? Why or why not?

class Object
  def median...
  def first_quartile...
  def third_quartile...
end

What if an instance of Array contains non-Numeric values?