Method CSVParser

src/io/parser.hpp:20–22

class CSVParser: public Parser {
 public:
  explicit CSVParser(int label_idx, int total_columns)
    :label_idx_(label_idx), total_columns_(total_columns) {
  }
  inline void ParseOneLine(const char* str,
    std::vector<std::pair<int, double>>* out_features, double* out_label) const override {
    int idx = 0;