s="variablelist"><table border="0"><col align="left" /><tbody><tr><td><span class="term"><i><tt>ctxt</tt></i>:</span></td><td>the expressions context</td></tr><tr><td><span class="term"><i><tt>exp</tt></i>:</span></td><td>the englobing expression</td></tr><tr><td><span class="term"><i><tt>sub</tt></i>:</span></td><td>the subexpression</td></tr><tr><td><span class="term"><i><tt>Returns</tt></i>:</span></td><td>1 if true 0 if false and -1 in case of failure.</td></tr></tbody></table></div><h3><a name="xmlRegE