Problem 4

 1num = 999;
 2current_palin = 0;
 3loop do
 4    second_num = 999;
 5    loop do
 6        current_product = num * second_num;
 7        if current_product.to_s.reverse ==  current_product.to_s 
 8            if current_palin < current_product 
 9                current_palin = current_product.to_i;
10            end
11        end
12        second_num -= 1;
13        if second_num < 100 
14            break;
15        end
16    end
17    num -= 1;
18    if num < 100 
19        break;
20    end
21end
22puts"#{current_palin}";

 1(ns problem4.core)
 2
 3(defn is-palindrome?
 4  [num]
 5   (= (str num) (apply str (reverse (str num)))))
 6
 7(defn get-val
 8  [num]
 9  (cond 
10    (= (is-palindrome? num) true) num
11    :else 0))
12
13(defn cart-prod 
14  []
15  (for [x (range 100 1000)
16        y (range 100 1000)]
17    (* x y)))
18
19(defn -main
20  []
21  (println (apply max (map get-val (cart-prod)))))

1say max ([X*] (100..999, 100..999)).grep: {.flip eq $_}