Neighbours in clojure - simple & overengineered solutions

neighbours.clj

(defn neighbours-simple [[x y]]
  #{[(dec x) (dec y)] [x (dec y)] [(inc x) (dec y)]
    [(dec x)      y ]             [(inc x)      y]
    [(dec x) (inc y)] [x (inc y)] [(inc x) (inc y)]})

(defn neighbours-zipped [[x y]]
  (let [axis (juxt dec identity inc)]
    (clojure.set/difference 
      (set (mapcat (partial map vector)
                   (repeat (axis x))
                   (map repeat (axis y))))
      #{[x y]})))

; amalloy suggests (but with let-before-fn, for performance, which looks weird to me)
; NB: ordering of 0 unit first + `rest` removes original pos
(defn neighbours-amalloy [pos]
  (let [units [0 1 -1]
        deltas (rest (for [dx units, dy units] [dx dy])) 
        +pos (partial map + pos)]
    (set (map +pos deltas))))