comparable.rb

class Foo
  include Comparable

  attr_accessor :x, :y, :z

  def initialize(x,y,z)
    @x, @y, @z = x,y,z
  end

  def <=>(other)
    x == other.x &&
    y == other.y &&
    z == other.z
  end
end

f1 = Foo.new(1,2,3)
f2 = Foo.new(1,2,3)
f3 = Foo.new(2,3,4)

p f1 == f2
p f1 == f3

# compare_test.rb:21: warning: Comparable#== will no more rescue exceptions of #<=> in the next release.
# compare_test.rb:21: warning: Return nil in #<=> if the comparison is inappropriate or avoid such comparison.