public void visit(OpLabel opLabel) {
   if (opLabel.hasSubOp()) push(eval(opLabel.getSubOp()));
   else
     // No subop.
     push(TableFactory.createUnit());
 }
 @Test
 public void testOp_04() {
   opSame("(label 'ABC' (table unit))", OpLabel.create("ABC", OpTable.unit()));
 }