Changes for clojure.core/next

boxie on Sat, 06 Nov 2010
user=> (next '(:alpha :bravo :charlie))
(:bravo :charlie)

user=> (next (next '(:one :two :three)))
(:three)

user=> (next (next (next '(:one :two :three))))
nil
dpritchett on Tue, 13 Jul 2010
user=> (next '(:alpha :bravo :charlie))
(:bravo :charlie)