
    <graphical_slider_tool>
      <render>
<slider var='a' style="width:400px;float:left;"/><plot style="margin-top:15px;margin-bottom:15px;"/>
      </render>
      <configuration>
        <parameters>
            <param var="a" min="5" max="25" step="0.5" initial="12.5" />
        </parameters>
        <functions>
          <function color="red">return Math.sqrt(a * a - x * x);</function>
          <function color="red">return -Math.sqrt(a * a - x * x);</function>
        </functions>
        <plot>
          <xrange>
            <!-- dynamic range -->
              <min>
                  return -a;
              </min>
              <max>
                  return a;
              </max>
          </xrange>
          <num_points>1000</num_points>
          <xticks>-30, 6, 30</xticks>
          <yticks>-30, 6, 30</yticks>
        </plot>
      </configuration>
    </graphical_slider_tool>

