 std::cout &lt;&lt; &quot;Fred's old age: &quot; &lt;&lt; old_age &lt;&lt; &quot;\n&quot;
            &lt;&lt; &quot;Fred's old gpa: &quot; &lt;&lt; old_gpa &lt;&lt; &quot;\n&quot;;

  std::string new_age = &quot;18&quot;;
  double new_gpa = 3.9;
  put(&quot;age&quot;,properties,fred,new_age);
  put(&quot;gpa&quot;,properties,fred,new_gpa);
}
</pre>
<p>The new function is not a template parameterized on the property map
types but instead a concrete function that takes a <tt class="docutils literal"><span cl