- (class x) returns per-type JVM class names (Long/Double/Ratio/Character/Atom),
not a blanket java.lang.Number.
- register fully-qualified class tokens (java.lang.Long, clojure.lang.Keyword,
clojure.lang.Atom, ...) that self-evaluate to their name, so (= (class 1)
java.lang.Long) and (instance? clojure.lang.Atom x) resolve.
- instance? recognizes Long/Double/Ratio/Character/Symbol/Atom/IFn built-ins.
Closes class number/string/keyword/name, instance? Atom, atom?. Corpus 2699->2705.