Standard example of destructuring: calculating the slope of a line

destructuring_slope_of_a_line.clj

; representation of a line defined by two points
(def l [[1 2] [2 4]])

;information extracted on demand, actual calculation obscure  
(defn slope 
  [line] 
  (/
    (- (first (first line)) (first (second line)))
    (- (second (first line)) (second (second line)))))

;argument pre-processed, pieces of information print-named
;actual computation clear, but explicit naming tedious 
(defn slope2
  [line]
  (let [p1 (first line)
        p2 (second line)
        x1 (first p1)
        y1 (second p1)
        x2 (first p2)
        y2 (second p2)]
    (/ (- x1 x2) (- y1 y2))))

; win-win with destructuring  
(defn slope3
  [[[x1 y1] [x2 y2]]]
  (/ (- x1 x2) (- y1 y2)))