little Clojure hack to find functions by their behavior, like Smalltalk method finder

gistfile1.clj

(defn find-functions [pred]
  (let [pred (fn [fun]
               (binding [*out* nil *err* nil clojure.test/*test-out* nil]
                 (try (pred fun)
                      (catch Throwable t false))))
        excluded #{'clojure.core/read-line 'clojure.main/repl-read}]
    (for [ns (all-ns)
          [name fun] (ns-publics ns)
          :let [sym (symbol (str (ns-name ns)) (str name))] 
          :when (not (excluded sym))
          :when (ifn? fun)
          :when (pred fun)]
      sym)))

Examples:

user> (find-functions #(= (% "foo") "oof"))
(clojure.string/reverse)
user> (find-functions #(= (% "foo") "FOO"))
(clojure.string/upper-case)
user> (find-functions #(and (% (fn [x] x)) (not (% 17))))
(clojure.test/function? clojure.core/fn? clojure.core/ifn?)