title: Angular ng-show if string not empty does not work
body: <p>I am writing a web app using AngularJS. The user submits up to 3 keywords to the server. I would like to show commas in between the keywords only if there are enough keywords.</p>
  
  <p>For example:</p>
  
  <p>if there are no keywords, then: </p>
  
  <p>if there is 1 keyword, then: keyword</p>
  
  <p>if there are 2 keywords, then: keyword, keyword</p>
  
  <p>if there are 3 keywords, then: keyword, keyword, keyword</p>
  
  <p>I have the following code: </p>
  
  <pre><code>    &lt;tr&gt;
         &lt;td&gt;Keywords: &lt;/td&gt;
         &lt;td&gt;{{post.Keyword1}} &lt;span ng-show = "{{post.Keyword2}}"&gt;,&lt;/span&gt; {{post.Keyword2}} &lt;span ng-show = "{{post.Keyword3}}"&gt;,&lt;/span&gt; {{post.Keyword3}}&lt;/td&gt;
      &lt;/tr&gt;
  </code></pre>
  
  <p>Why does this not work?</p>