irb(main):026:0> objects = [1,1,1,2]
=> [1, 1, 1, 2]
irb(main):027:0> dups = objects.all? {|object| !set.add?(object).nil?}
=> false
irb(main):028:0> dups = objects.all? {|object| !set.add?(object)}
=> false
irb(main):029:0> objects = [1,2,3]
=> [1, 2, 3]
irb(main):030:0> dups = objects.all? {|object| !set.add?(object)}
=> true
irb(main):031:0> dups = objects.all? {|object| set.add?(object)}
=> false
irb(main):032:0> objects = [1,1,1,2]
=> [1, 1, 1, 2]
irb(main):033:0> dups = objects.all? {|object| set.add?(object)}
=> false