Rcpp, Iterate DataFrame

Question

I'm trying to realize a simple interop "R+Rcpp" and have strange problem with DataFrame::iterator and std::algorithm methods.

I have this code written on Rcpp.

struct TradeIndex
{
  Date date;
  
  long startIndex;
  long finishIndex;
  
  TradeIndex(Environment &tradeIndex)
  {
    date = Date(tradeIndex["Date"]);
    
    startIndex = Rcpp::as<long>(tradeIndex["StartIndex"]) - 1;
    finishIndex = Rcpp::as<long>(tradeIndex["FinishIndex"]) - 1;
  }
};

struct Asset
{
  std::string name;
  
  DataFrame ticks;
  std::vector<TradeIndex> indexes;
  
  DataFrame highQuantiles;
  DataFrame lowQuantiles;
  
  Asset(Environment &asset)
  {
     ticks = Rcpp::as<DataFrame>(asset["Ticks"]);
     indexes = std::vector<TradeIndex>();
      
     auto &&rawIndexes = Rcpp::as<List>(asset["Indexes"]);
     
     std::for_each(rawIndexes.begin(), rawIndexes.end(), [this](auto &&elem) 
     { 
        auto RElem = Rcpp::as<Environment>(elem);
        this->indexes.push_back(TradeIndex(RElem)); 
     });
      
     highQuantiles = Rcpp::as<DataFrame>(asset["HighQuantiles"]);
     lowQuantiles = Rcpp::as<DataFrame>(asset["LowQuantiles"]);
      
     name = Rcpp::as<std::string>(asset["Name"]);
  }
};


// [[Rcpp::plugins(cpp17)]]
// [[Rcpp::depends(BH)]]
// [[Rcpp::export]]
List StrategyRealization(Environment &RAsset, double basePortfolioMoney, double comission, Date startDate, Date endDate, 
                         std::string &open, std::string &stopLoss, std::string &takeProfit, int direction, double damperLvl)
{
  std::cout << "Started calculation" << std::endl;
  
  string directionString = direction == 1 ? "long" : "short";
  
  auto RAssetDataElem = Rcpp::as<Environment>(RAsset);
  auto asset = Asset(RAssetDataElem);
  
  auto &&quantiles = direction == 1 ? asset.lowQuantiles : asset.highQuantiles;
  
  auto &&quantileIterator = std::find_if(quantiles.begin(), quantiles.end(), [&startDate](DataFrame &&elem) 
  {
      DateVector &&dateVector = elem["Date"];
      return Date(dateVector[0]) == startDate; 
  });

  ...
}

Here highQuantiles and lowQuantiles are DataFrames with columns Date, q1, q2, q3, where Date is a date vector, q1, q2, q3 are numeric vectors.

But this code crashes.

If I write code like this

  auto &&quantileIterator = std::find_if(quantiles.begin(), quantiles.end(), [&startDate](auto &&elem) 
  {
      DateVector &&dateVector = elem["Date"];
      return Date(dateVector[0]) == startDate; 
  });

I get <Rcpp::not_compatible in eval(ei, envir): Expecting a single value: [extent=813].> error.

Please, could you explain me why?

Where can I read about iterators for DataFrame, List, GenericVector.