title: LLVM Compiler 2.0: Warning with "using namespace std;"
body: <p>In Xcode using LLVM 2.0, when I put the line <code>using namespace std;</code> in my C++ code, I get this warning:  </p>
  
  <blockquote>
    <p>Semantic Issue<br>
        Using directive refers to implicitly-defined namespace 'std'</p>
  </blockquote>
  
  <p>Is there a way to fix this?  Why is it giving that warning?</p>