#!/usr/bin/env ruby
# This code comes from http://ruby-it.org/pages/Comparable
# Check the page for copyright notice and explanations



>> 5 <= 5.0
=> true
>> 4 > 4
=> false
>> "a" < "b"
=> true

>> class Person
>>  attr_reader :name
>>  def initialize(name)
?>   @name= name
>>  end
>>  def == other
?>   name == other.name
>>  end
>> end
=> nil

>> p1=Person.new "joe"
=> #<Person:0xb7d2abac @name="joe">
>> p2=Person.new "joe"
=> #<Person:0xb7d26854 @name="joe">
>> p1 == p2
=> true

>> p1 < p2
NoMethodError: undefined method `<' for #<Person:0xb7d2abac @name="joe">
        from (irb):57
        from (null):0

>> class Person
>>  include Comparable # includiamo il Mixin
>>  attr_reader :name
>>  def initialize(name)
?>   @name= name
>>  end

>>  # definiamo lo spaceship operator
>>  def <=> other
?>   name <=> other.name
>>  end
>> end
=> nil

>> p1=Person.new "joe"
=> #<Person:0xb7cfac40 @name="joe">
>> p1=Person.new "john"
=> #<Person:0xb7cf4084 @name="john">
>> p1=Person.new "joe"
=> #<Person:0xb7ced450 @name="joe">
>> p2=Person.new "john"
=> #<Person:0xb7ce8d4c @name="john">
>> p3=Person.new "james"
=> #<Person:0xb7ce3860 @name="james">
>> p1 != p3
=> true
>> p1 < p3
=> false
>> p1 > p3
=> true
>> p2 >= p3
=> true