protocolsince v0.0-927Edit
implemented for ArrayNodeSeq BlackNode ChunkedCons ChunkedSeq Cons Cycle EmptyList IndexedSeq IntegerRange Iterate KeySeq LazySeq List MapEntry NodeSeq ObjMap PersistentArrayMap PersistentArrayMapSeq PersistentHashMap PersistentHashSet PersistentQueue PersistentQueueSeq PersistentTreeMap PersistentTreeMapSeq PersistentTreeSet PersistentVector RSeq Range RedNode Repeat Subvec ValSeq

Source docstring:
Protocol for creating an empty collection.
Source code @ clojurescript:src/main/cljs/cljs/core.cljs
(defprotocol IEmptyableCollection
  (-empty [coll]
    "Returns an empty collection of the same category as coll. Used
     by cljs.core/empty."))