private final static boolean needPermute__(Node expr, Node n_left, Node n_right) throws Exception {
//System.out.println("nleft:"+n_left+ " : nright:"+n_right);
Node argv = Node.createCList();
argv.addElement(n_left);
argv.addElement(n_right);
Heap.push(); // nouvel espace local
Heap.defv(ASymbol.SYMBOL_ARGV, argv);
Node rnode = expr.exec(true);
Heap.pull(); // supprimer l'espace local...
return Node.isTrueEquivalent(rnode);