gistfile1.clj

(defn map-lr-vecs [f v]
  (reduce (fn [result index]
	    (conj result
		  (f (subvec v 0 index)
		     (get v index)
		     (subvec v (inc index)))))
	  []
	  (range (count v))))

(map-lr-vecs (fn [left val right]
	       (println [left val right])
	       val)
	     [1 2 3 4 5 6])

[[] 1 [2 3 4 5 6]]
[[1] 2 [3 4 5 6]]
[[1 2] 3 [4 5 6]]
[[1 2 3] 4 [5 6]]
[[1 2 3 4] 5 [6]]
[[1 2 3 4 5] 6 []]
[1 2 3 4 5 6]