ty </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>
% </html>

%%
% <html>
% <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> <co