n>
    <span class="keyword">typedef</span> <span class="identifier">S</span>               <span class="identifier">source_type</span> <span class="special">;</span>
    <span class="keyword">typedef</span> <span class="special">{</span><span class="identifier">S</span> <span class="keyword">or</span> <span class="identifier">S</span> <span class="keyword">const</span><span class="special">&amp;}</span> <span class="identifier">argument_type</span> <span class="special">;</span>

    <span class="keyword">