docs: public Operator operator(final Token tok) throws Exception
      {
          final String token = tok.getValue().toString();
          final Constructor<?> constructor = operatorMap.get(token);
          if (constructor == null)
              return null;
          try
          {
              return (Operator) constructor.newInstance(new Object[] {
                      tok
              });
          } catch (final Exception e)
          {
              throw new Exception("operator construction", e);
          }
      }