title: printf remove the tail 0s
body: <p>I have two double number <code>a</code> and <code>b</code></p>
  
  <pre><code>double a = 1.01, b = 1.2345678
  </code></pre>
  
  <p>then <code>printf("%.4f %.4f", a, b)</code> will output</p>
  
  <pre><code>1.0100  1.2345
  </code></pre>
  
  <p>but I want to output </p>
  
  <pre><code>1.01 1.2345
  </code></pre>
  
  <p>that is, remove the useless 0s. </p>