colors-by-basicness.clj

(def all-bit-length-triples
  (sort-by (fn [a] (vec (cons (apply max a)
                              (concat
                               (sort a)
                               a))))
           (for [a (range 9), b (range 9), c (range 9)]
             [a b c])))

(defn bindex
  "Given a number in (range 256), returns the position of the rightmost                                                                          
  set bit, where 0 returns 0 and 1 returns 8."
  [n]
  (if (= 255 n)
    0
    (loop [x 8, n n]
      (if (or (zero? x) (odd? n))
        x
        (recur (dec x) (/ n 2))))))

(defn numbers-by-bindex
  [n]
  (filter (comp #{n} bindex) (range 256)))

(def all-colors
  (for [[r g b] all-bit-length-triples,
        r' (numbers-by-bindex r)
        g' (numbers-by-bindex g)
        b' (numbers-by-bindex b)]
    [r' g' b']))