title: C++ template function default value
body: <p>Is it possible to define the default value for variables of a template function in C++?</p>
  
  <p>Something like below:</p>
  
  <pre><code>template&lt;class T&gt; T sum(T a, T b, T c=????)
  {
       return a + b + c;
  }
  </code></pre>