title: Using namespaces and includes
body: <p>The question might be trivial (and possibly a duplicate).</p>
  
  <p>As far as I understand, a C/C++ header file (with a <code>using namespace</code> in it), when used by other source files, it is copied right at the point where the <code>#include</code> directive was in that source file.</p>
  
  <p>Also, given that a source file uses a relatively large number of include directives and that there may be a couple of "redefinitions" for the entire standard library (simply targeted at different implementations).</p>
  
  <p>Here is the main question: <strong>How do I know which namespaces am I currently using at any point in the source file if the source file has no <code>using namespace</code> statement?</strong></p>
  
  <p>I'm reading through source files and I have no idea which namespace is being used.</p>
  
  <p>One can override the namespace cleverness by using something like <code>::std::getline()</code>.</p>
  
  <p>If there is no easy way of determining the namespace, is it fair to refactor those files, such that where say <code>string</code> is used to replace it with <code>::std::string</code>?</p>