04-euler.clj

(defn palindromic? [n]
  (let [straight (seq (str n))
        reversed (reverse straight)]
    (= straight reversed)))

(palindromic? 9009) ; true
(palindromic? 909) ; true
(palindromic? 1023) ; false

(defn combination [seq1 seq2]
  (for [x seq1
        y seq2]
    [x y]))

(defmacro combination [& seqs]
  (let [seq-var (map (fn [x] [(gensym) x]) seqs)]
    `(for [~@(apply concat seq-var)]
       [~@(->> seq-var
               (map #(first %))
               flatten )])))

(combination [1 2 3] [4 5 6] [7 8 9 10])

(println
 (let [search-range (range 100 1000)
       all-combinations (combination search-range search-range)]
   (->> all-combinations
        (map (fn [[a b]] (* a b)))
        (filter palindromic?)
        (apply max))))