Jim Weirich wrote:
>  ...
> The hash function should return an integer to be used for hashing.  Your 
> version returns a string.  One correction might be ...
> 
>   def hash
>     [@x.object_id, @y.object_id].to_s.hash
>   end
> 
> That will now work.  But you probably really don't want to bother converting 
> the above to a string.  Why not just do:
> 
>   def hash
>     @x.object_id + @y.object_id
>   end

Isn't this the same value as

   @y.object_id + @x.object_id

giving, for example,

PointID.new( 1, 2).hash ==  PointID.new( 2, 1).hash


But they are different coordinates.

James