title: using string to pass filename to fstream
body: <p>I am using the following method to read a txt file</p>
  
  <pre><code>modelStream.open("file.txt", ios::in);
  if (modelStream.fail())
      exit(1);
  model = new Model(modelStream);
  </code></pre>
  
  <p>but i want to know how i can pass in a string as a parameter</p>
  
  <pre><code>string STRING;
  modelStream.open(STRING, ios::in);
  if (modelStream.fail())
      exit(1);
  model = new Model(modelStream);
  </code></pre>
  
  <p>does anyone know if this is possible and if it is how would I do it?</p>