honebook</span><span class=special>;</span>
</pre></blockquote>

In this example, the first usage of <code>key</code> substitutes for the
decidedly more cumbersome:

<blockquote><pre>
<span class=identifier>composite_key</span><span class=special>&lt;</span>
  <span class=identifier>phonebook_entry</span><span class=special>,</span>
  <span class=identifier>member</span><span class=special>&lt;</span><span class=identifier>phonebook_entry</span><span class=special>,</span><span class=identifier>std</span><s