title: 'For' loop pre and post empty statements
body: <p>What does it mean in Go that the pre and post statements of a <em>for</em> loop are empty, like in the following example?</p>
  <pre><code>    sum := 1
      for ; sum &lt; 10; {
          sum += sum
      }
      fmt.Println(sum)
  </code></pre>