fluids.clj

(defmacro do-board [[w h] & body]
  `(let [w# (int ~w) h# (int ~h)]
     (loop [~'i (int 1)]
       (when (< ~'i h#)
	 (loop [~'j (int 1)]
	   (when (< ~'j w#) 
	     (do ~@body)
	     (recur (unchecked-inc ~'j))))
	 (recur (unchecked-inc ~'i))))))

(defmacro map! [f lookup collection ]
  `(let [[w# h#] [(count ~lookup) (-> ~lookup first count)]]
     (let [board# (make-array Double/TYPE h# w#)]
;       (dotimes [k# 20]	   o
       (do-board [w# h#]
	 (let [~'above  (deep-aget ~'doubles ~lookup (unchecked-dec ~'i) ~'j)
		 ;              (aget ~lookup (dec ~'i) ~'j)
	       ~'below  (deep-aget ~'doubles ~lookup (unchecked-inc ~'i) ~'j)
	       ~'left   (deep-aget ~'doubles ~lookup ~'i (unchecked-dec ~'j))
	       ~'right  (deep-aget ~'doubles ~lookup ~'i (unchecked-inc ~'j))
	       ~'self   (deep-aget ~'doubles ~lookup ~'i ~'j)]
	   (deep-aset ~'doubles board# (int ~'i) (int ~'j) ~f)))
       board#)))

(defn diffuse-board
  [board diffusion]
  (let [sz         (count board)
	dr         (* *dt* diffusion sz sz)]
    (map! (min 255.0 (/ (+ self (* dr (+ (+ above below) (+ left right))))
			      (inc (* 4 dr))))
		board (make-array Double/TYPE sz sz))))