'u</span><span
      class="cp">&gt;</span></code> and in particular constrains the type of its argument to <code class="fsharp"><a
      href="../reference/charstream.html#CharStream"><span class="ci">CharStream</span></a><span class="cp">&lt;</span><span
      class="ctv">'u</span><span class="cp">&gt;</span></code>. Remember, the type <code class="fsharp"><a
      href="../reference/primitives.html#members.Parser"><span class="ci">Parser</span></a><span class="cp">&lt;</span><span
      class="ctv">'a</s