title: My std::exchange is not in namespace std?
body: <p>I included <code>&lt;utility&gt;</code> in my source file. Then I used <code>std::exchange</code>, but the compiler said it didn't found <code>exchange</code> in the namespace std. I looked at <code>usr/include/utility</code>, and by searching <code>exchange</code> I found the implementation, and it's inside the <code>namespace std</code> block. I had to remove <code>std::</code> from <code>std::exchange</code> to make the code compile.</p>
  
  <p>Can I solve this?</p>
  
  <p>How can I make my code portable otherwise?</p>
  
  <p>Note: I am using clang from the Termux linux emulator on Android. I got clang by installing it with <code>apt</code>.</p>