Namespaces

Every namespace has its own vars: a definition belongs to the current namespace, a name resolves to that namespace's own var and then to a referred one, and alias/name or full.name/name reaches another namespace's public var. A namespace form switches to its namespace and wires its clauses: :as registers an alias, :refer/:use unqualified names, :import class names for interop, (:refer-clojure :only/:exclude ...) narrows the visible core; metadata on the name (^{...}, #^{...}), a docstring and an attr map are skipped. clojure.string, clojure.set, clojure.java.io (reader only) and clojure.test are built in; any other namespace is one the program declares with ns, or one loaded once from its file on the source path (Semantics). A namespace no root holds is an error.