title: How to recursively enumerate all possible arrays where each element has an upper bound?
body: <p>For example, I want to enumerate all arrays in the range <code>[0,0,0,0] ~ [3,4,5,6]</code>.</p>
  
  <p>I can access whole possible cases with loops but my brain fried when I try to implement it recursively.</p>
  
  <p>I know it is a kind of useless questions myself but curious.</p>