title: Why does each_slice with block and .map return nil
body: <p>Why does this return nil and what does line 2 mean? The array represents rows of a Sudoku puzzle which I'm trying to create a solution for. </p>
  
  <p>I'm trying different methods in irb to see how many different ways I can view the array. </p>
  
  <pre><code>array = ['015003002000100906270068430490002017501040380003905000900081040860070025037204600']
  array.each_slice(9) { |e| puts e.map }
  #&lt;Enumerator:0x0000010288a470&gt;
  =&gt; nil
  </code></pre>