gistfile1.clj

(defn and-seq 
  ([e]
     (list e))
  ([e & es]
     (letfn [
	     (and-seq* ([e] (list "and" e))
		       ([e & es] (lazy-seq (concat (list "," e) (apply and-seq* es)))))]
       (conj (apply and-seq* es) e))))

(defn and-seq 
  ([e] (list e))
  ([e & es]
     (letfn [(and-seq* [e] 
		       (let [[f & r] e]
			 (if r
			   (lazy-seq (concat  (list "," f) (and-seq* r)))
			  (list "and" f))))]
       (conj (and-seq* es) e))))


(defn combiner 
  ([m] (combiner m m))
  ([m l]
     (fn
       ([e] (list e))
       ([e & es]
	  (letfn [(and-seq* [e] 
			    (let [[f & r] e]
			      (if r
			     (lazy-seq (concat  (list m f) (and-seq* r)))
			     (list l f))))]
	    (conj (and-seq* es) e))))))

((combiner "," "and") 1 2 3)

(apply str ((combiner ", " " and ") 1 2 3))