offset.clj

(defn square [x] (* x x))

(defn offset [x y]
  (let [ms (max (Math/abs x) (Math/abs y))
        sq (dec (* 2 ms))
        base (square sq)
        side (inc sq)
        hside (/ side 2)]
    (cond
      (and (= x ms) (< y ms)) (- (+ base hside) y)
      (= y (- ms)) (- (+ base side hside) x)
      (= x (- ms)) (+ base (* 2 side) hside y)
      (= y ms) (+ base (* 3 side) hside x))))