"This demonstration defines a class of objects
of type Delivery which are house numbers and the
name of the recipient. The postman needs to see
which object to deliver first and which second,
and in order to do so he goes up the even numbers
then back down the odd numbers.

For readers who are not from the UK, British streets
are usually numbered back and forth across the road
so that you have 1,3,5,7 etc on one side and 2,4,6,8
etc on the other. And with modern busy traffic, the
postman does NOT want to keep crossing!!"

class Delivery
   include Comparable
   def initialize(number,name)
      @name=name
      @number=number
   end
   def getnumber
      @number
   end
   def <=> (partner)
      print "I'll ask Jess\n"
      return -1 if @number.modulo(2) != 0 and partner.getnumber.modulo(2) == 0
      return 1 if @number.modulo(2) == 0 and partner.getnumber.modulo(2) != 0
      return partner.getnumber <=> @number if @number.modulo(2) == 0
      return @number <=> partner.getnumber
   end
   def to_s
      "Deliver to #{@name} at #{@number}"
   end
end

gordon = Delivery.new(10,"Mr Dodge")
graham = Delivery.new(404,"Mr Ellis")
reggie = Delivery.new(22,"Dr Dodson")
kim = Delivery.new(25,"Ms Ellis")
chris = Delivery.new(15,"Mr Ellis")

print kim," before ",chris,"\n" if kim < chris
print chris," before ",kim,"\n" if kim >= chris

print reggie," before ",chris,"\n" if reggie < chris
print chris," before ",reggie,"\n" if reggie >= chris

print reggie," before ",graham,"\n" if reggie < graham
print graham," before ",reggie,"\n" if reggie >= graham

print reggie," before ",gordon,"\n" if reggie < gordon
print gordon," before ",reggie,"\n" if reggie >= gordon

print reggie," before ",kim,"\n" if reggie < kim
print kim," before ",reggie,"\n" if reggie >= kim