brevity.rb

class P
  def initialize x, y
    @x, @y = x, y
  end
  attr_reader :x, :y
  
  def d p
    Math.sqrt((p.x - x) + (p.y - y))
  end
end

clarity.rb

class Point
  def initialize x_coordinate, y_coordinate
    @x_coordinate = x_coordinate
    @y_coordinate = y_coordinate
  end
  attr_reader :x_coordinate, :y_coordinate
  
  def distance_to other_point
    x_difference = other_point.x_coordinate - self.x_coordinate
    y_difference = other_point.y_coordinate - self.y_coordinate
    Math.sqrt x_difference + y_difference
  end
end