condr.clj

(defn condr*
  [& goals]
  (if (= 1 (count goals))
    (first goals)
    (let [goals (shuffle goals)]
      (conde
       [(first goals)]
       [(apply condr* (rest goals))]))))
 
(defmacro condr
  "Same as conde but clauses are scrambled on each call."
  [& clauses]
  `(condr* ~@(for [clause clauses] (cons `all clause))))
 
 
;; example usage
 
(defn listso
  [x]
  (condr
   [(membero x [:a :b :c])]
   [(== [] x)]
   [(fresh [a b] (listso a) (listso b) (== [a b] x))]))