class Addressbook
	def initialize
		@persons = []   #empty array
		end
	def add(person)
		@persons += [person]
		@persons.sort { |a,b| by_name(a,b) }
		end
	def remove(person)
		@persons.delete(person) #uses Array#delete method
		end
		
	#automatic sorting!
	def by_name(a,b)
		if a.first_name == b.first_name
			a.last_name <=> b.last_name
		else
			a.first_name <=> b.first_name
		end
 	end
 	
 	def to_s
 		@persons.each do |elem|
 		 	puts elem
 		end
 	end
end