code: @Override
      public void resolve(final ValueStack values) throws Exception
      {
          if (getEqu().getSupport() == null)
              throw new Exception("variables require support");
  
          final Object obj = getEqu().getSupport().resolveVariable(
                  getValue().toString().toLowerCase(),
                  getEqu().getBaseDate());
          if (obj == null)
          {
              /*
               * The variable may not exist if it is the target of an assignment
               * operation. The variable will be created rather than resolved.
               * Further, variables are final.
               */
              values.push(this);
              assignedByEquation = true;
          } else
              values.push(obj);
      }
docs: {@inheritDoc}