ar <code class="fsharp"><a href="../reference/charstream.html#CharStream.members.Index"><span
      class="ci">Index</span></a></code>, which uniquely identifies the UTF‐16 char in the stream. In addition to the index of the next char, the
      <code class="fsharp"><a href="../reference/charstream.html#CharStream"><span class="ci">CharStream</span></a></code> also keeps track of char’s
      <code class="fsharp"><a href="../reference/charstream.html#CharStream.members.Line"><span class="ci">Line</span>