code: public boolean equivalent(final CronMapper cronMapper, final Cron cron) {
          return asString().equals(cronMapper.map(cron).asString());
      }
docs: Provides means to compare if two cron expressions are equivalent.
  
  @param cronMapper - maps 'cron' parameter to this instance definition;
  @param cron       - any cron instance, never null
  @return boolean - true if equivalent; false otherwise.