title: Pass a reference to std::ifstream as parameter
body: <p>I'm trying to write a function with an <code>ifstream&amp;</code> argument.</p>
  
  <pre><code>void word_transform(ifstream &amp; infile)
  {
      infile("content.txt");
      //etc
  }
  </code></pre>
  
  <p>which gave me an error:</p>
  
  <blockquote>
    <p>Type 'ifstream' (aka 'basic_ifstream ') does not provide a call operator.</p>
  </blockquote>
  
  <p>Can you please me what's wrong?</p>