On Sat, Jun 5, 2010 at 8:55 PM, Rein Henrichs <reinh / reinh.com> wrote: <snip> > The Array#& operator, like its siblings, uses the #hash and #eql? methods of > the objects it compares. These must be the same for objects you want to be > considered equivalent. > I must have made a stupid mistake in my example code, however, this is no reason to mess with #eql? and #hash, Be warned. In that case I stick with Robert's advice: Do not use Array#&, even MPing Array with something like #intersect_by would be preferable. Cheers Robert