ref="annotation.html#spirit_x3.tutorials.annotation.x3__position_cache">x3::position_cache</a>
      </h5>
<p>
        Before we proceed, let me introduce a helper class called the <code class="computeroutput"><span class="identifier">position_cache</span></code>. It is a simple class that
        collects iterator ranges that point to where each element in the AST are
        located in the input stream. Given an AST, you can query the position_cache
        about AST's position. For example:
      </p>
<p