Returns true if argument is a function or a symbol that resolves to a function (not a macro).
user> (defn foo [] (println "foo")) #'user/foo user> (def bar "bar") #'user/bar user> (clojure.test/function? foo) true user> (clojure.test/function? bar) false
Returns true if x implements Fn, i.e. is an object created via fn.
function?