lass="identifier">my_expr</span>
<span class="special">{</span>
    <span class="comment">// OK, this makes my_expr&lt;&gt; a valid Proto expression extension.</span>
    <span class="comment">// my_expr&lt;&gt; does /not/ have overloaded assignment, subscript,</span>
    <span class="comment">// and function call operators that build expression templates, however.</span>
    <a class="link" href="BOOST_PROTO_BASIC_EXTENDS.html" title="Macro BOOST_PROTO_BASIC_EXTENDS">BOOST_PROTO_BASIC_EXTENDS</a><span clas