 to perform optimization
      decisions at compile-time. Another important usage of type traits is to allow
      code to compile that otherwise would not do so unless excessive partial specialization
      is used. This is possible by delegating partial specialization to the type
      traits classes. Our example for this form of usage is a pair that can hold
      references <a class="link" href="background.html#background.references">[6]</a>.
    </p>
<p>
      First, let us examine the definition of <c