n></code><code class="computeroutput"><span class="special">[</span><span class="identifier">p</span><span class="special">]</span></code>)
        requires that the argument parser matches the input or an exception is emitted.
        Using on_error(), that exception can be handled by calling a handler with
        the context at which the parsing failed can be reported.
      </p>
<h5>
<a name="spirit_x3.tutorials.error_handling.h2"></a>
        <span class="phrase"><a name="spirit_x3.tutorials.error_hand