How do you replace Java nested for loops in Clojure?

Question

I have created a very simple nested loop example and am struggling to write the equivalent Clojure code. I've been trying to do it by list comprehensions but cannot get the same answer. Any help appreciated.

public class Toy {

    public static void main(String[] args) {
        int maxMod = 0;
        for (int i=0;i<1000;i++) {
            for (int j=i;j<1000;j++) {
                if ((i * j) % 13 == 0 && i % 7 == 0) maxMod = i * j;
            }
        }
        System.out.println(maxMod);
    }
}

Answer 1

Here's a list comprehension solution:

(last 
  (for [i (range 1000) 
        j (range 1000)
        :let [n (* i j)] 
        :when (and (= (mod n 13) 0) 
                   (= (mod i 7) 0))] 
    n))

Answer 2

In general, you want to use some sort of sequence operation (like dnolen's answer). However, if you need to do something that is not expressible in some combination of sequence functions, using the loop macro works as well. For this precise problem, dnolen's answer is better than anything using loop, but for illustrative purposes, here is how you would write it with loop.

(loop [i 0
       max-mod 0]
  (if (>= i 1000)
    (println max-mod)
    (recur (inc i)
           (loop [j 0
                  max-mod max-mod]
             (if (>= j 1000)
               max-mod
               (recur (inc j)
                      (if (and (= (mod (* i j) 13) 0)
                               (= (mod 1 7) 0))
                        (* i j)
                        max-mod)))))))

This is pretty much an exact translation of your given code. That said, this is obviously ugly, which is why a solution using for (or other similar functions) is preferred whenever possible.