From: "Kroeger, Simon (ext)" <simon.kroeger.ext@...>
Date: 2006-01-24T21:02:21+09:00
Subject: Re: Making Array#uniq work

> -----Original Message-----
> From: Damphyr [mailto:damphyr@freemail.gr] 
> Sent: Tuesday, January 24, 2006 12:35 PM
> To: ruby-talk ML
> Subject: Making Array#uniq work
> 
> OK, according to the Pickaxe 2nd. Edition, Array#uniq judges 
> uniqueness 
> based on eql?. Somehow this doesn't seem to work for me :).
> Following code returns the Array with two members instead of 
> the one I 
> would wish for. Any pointers? I'm running 1.8.2
 

Hi,

you have to define a 'hash' method because Array uses a Hash to remove
the duplicates.

e.g.:
----------------------------------------------------------
class A
   attr_accessor :a,:b
   def initialize a
     @a=a
     @b=Array.new
   end
   def << item
     @b<<item
   end
	
   def eql? other
     return true if @a==other.a && @b==other.b
   end
   
   def == other
     return eql?(other)
   end
   
   def hash
    a.hash * b.hash
   end
end


o1=A.new("a")
o2=A.new("a")
o1<<"o"
o2<<"o"
puts o1==o2
puts o1.eql?(o2)
p [o1,o2].uniq
---------------------------------------------------------- 

cheers

Simon