enum class  file_dtypes : std::size_t  {

    FLOAT = 0,            // float
    DOUBLE = 1,           // double
    LONG_DOUBLE = 2,      // long double
    SHORT = 3,            // short int
    USHORT = 4,           // unsigned short int
    INT = 5,              // int
    UINT = 6,             // unsigned int
    LONG = 7,             // long int
    ULONG = 8,            // unsigned long int
    LONG_LONG = 9,        // long long int
    ULONG_LONG = 10,      // unsigned long long int
    CHAR = 11,            // char
    UCHAR = 12,           // unsigned char
    BOOL = 13,            // bool

    STRING = 14,          // std::string
    VSTR8 = 15,           // FixedSizeString<7> == String8
    VSTR16 = 16,          // FixedSizeString<15> == String16
    VSTR32 = 17,          // FixedSizeString<31> == String32
    VSTR64 = 18,          // FixedSizeString<63> == String64
    VSTR128 = 19,         // FixedSizeString<127> == String128
    VSTR512 = 20,         // FixedSizeString<511> == String512
    VSTR1K = 21,          // FixedSizeString<1023> == String1K
    VSTR2K = 22,          // FixedSizeString<2047> == String2K

    DATETIME = 23,        // DateTime
    DATETIME_AME = 24,    // DateTime
    DATETIME_EUR = 25,    // DateTime
    DATETIME_ISO = 26,    // DateTime

    STR_DBL_PAIR = 27,    // std::pair<std::string, double>
    STR_STR_PAIR = 28,    // std::pair<std::string, std::string>
    DBL_DBL_PAIR = 29,    // std::pair<double, double>

    DBL_VEC = 30,         // std::vector<double>
    STR_VEC = 31,         // std::vector<std::string>
    DBL_SET = 32,         // std::set<double>
    STR_SET = 33,         // std::set<std::string>
    STR_DBL_MAP = 34,     // std::map<std::string, double>
    STR_DBL_UNOMAP = 35,  // std::unordered_map<std::string, double>
};