give `class grains def self.square(n) 2 ** (n - 1) end` like here: `class phrase < struct.new(:text)` a struct like: in ruby

To define a class in Ruby that inherits from Struct and also has a method, you can use the following syntax:

main.rb
class Phrase < Struct.new(:text)
  def self.square(n)
    2 ** (n - 1)
  end
end
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In this example, the Phrase class inherits from Struct and defines a single attribute :text. The self.square method is a class method that calculates the square of a given number.

You can access the text attribute and the square method on instances of the Phrase class:

main.rb
phrase = Phrase.new("Hello, World!")
puts phrase.text # Output: Hello, World!
puts Phrase.square(3) # Output: 4
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This allows you to define a class that has both data attributes and methods.