class Interval
  def initialize(min = Float::INFINITY, max = -Float::INFINITY)
    @min = min
    @max = max
  end

  attr_reader :min, :max

  def size
    @max - @min
  end

  def include?(x)
    min <= x && x <= max
  end

  def surround?(x)
    min < x && x < max
  end
end