e> </td> <td> Equality </td></tr>
<tr><td> <code>a & b</code> </td> <td> Logical AND </td></tr>
<tr><td> <code>a | b</code> </td> <td> Logical OR </td></tr>
<tr><td> <code>xor(a, b)</code> </td> <td> Logical exclusive OR </td></tr>
<tr><td> <code>~a</code>  </td> <td> Logical NOT </td></tr>
</table>
</p><p>
<table border="5" cellspacing="5">
<caption>Investigate logical trees</caption>
<tr><td> <code>any(a)</code>  </td> <td>  True if any node content is a nonzero number </td></tr>
<tr><td> <code>all(a)</co