gross_weight.rb

class GrossWeight
  include Comparable

  attr_reader :value

  def initialize(value)
    @value = value
  end

  def <=>(other)
    value <=> other.value
  end

  def succ
    self.class.new(value.succ)
  end
end

low = (...GrossWeight.new(40))
medium = (GrossWeight.new(40)..GrossWeight.new(50))

case GrossWeight.new(42)
in ^low
  :low
in ^medium
  :medium
else
  :high
end
#=> :medium