concato.clj

gistfile1.clj

(defn concato
  ([a b o]
     (appendo a b o))
  ([a b c & rest]
     (let [g (fresh [l]
               (appendo a b l)
               (apply concato l c rest))
           g' (fresh [l]
                (apply concato l c rest)
                (appendo a b l))]
       (conde
         [(lvaro a) (lvaro b) g']
         [(nonlvaro a) (lvaro g) g]
         [(lvaro a) (nonlvaro b) g]
         [(nonlvaro a) (nonlvaro b) g]))))

;; (run* [q]
;;   (concato '(1 2 3) '(4 5 6) '(7 8 9) q))

;; (run* [q]
;;   (fresh [x y]
;;     (concato x y x '[b a a a a a b])
;;     (== q y)))

I think this version also suffers from non-termination, for example:

(run* [q]
  (fresh [x y]
    (concato x y x '[b a a a a a b])
    (== q y)))

Should return something like ([b a a a a a b] [a a a a a]) but it doesn't terminate