ass=special>&gt;</span> <span class=identifier>phonebook</span><span class=special>;</span>
</pre></blockquote>

<p>
<code>composite_key</code> accepts two or more key extractors on the same
value (here, <code>phonebook_entry</code>). Lookup operations on a composite
key are accomplished by passing tuples with the values searched:
</p>

<blockquote><pre>
<span class=identifier>phonebook</span> <span class=identifier>pb</span><span class=special>;</span>
<span class=special>...</span>
<span class=comment>// 