de>all(a)</code>  </td> <td>  True if all node content are nonzero numbers </td></tr>
% </table>
% </html>
% 

%%
% Here is a list of operators that are *not* implemented, because they make
% sense only for matrices:
%
% <html>
% <table border="5" cellspacing="5">
% <tr><td> <code>a*b</code> </td> <td> Matrix multiplication </td></tr>
% <tr><td> <code>a/b</code> </td> <td> Matrix right division </td></tr>
% <tr><td> <code>a\b</code> </td> <td> Matrix left division </td></tr>
% <tr><td> <code>a^b</code> </td