RosettaCodeData/Task/Validate-International-Securities-Identification-Number/C++/validate-international-securities-identification-number.cpp

#include <string>
#include <regex>
#include <algorithm>
#include <numeric>
#include <sstream>

bool CheckFormat(const std::string& isin)
{
  std::regex isinRegEpx(R"([A-Z]{2}[A-Z0-9]{9}[0-9])");
  std::smatch match;
  return std::regex_match(isin, match, isinRegEpx);
}

std::string CodeISIN(const std::string& isin)
{
  std::string coded;
  int offset = 'A' - 10;
  for (auto ch : isin)
  {
    if (ch >= 'A' && ch <= 'Z')
    {
      std::stringstream ss;
      ss << static_cast<int>(ch) - offset;
      coded += ss.str();
    }
    else
    {
      coded.push_back(ch);
    }
  }

  return std::move(coded);
}

bool CkeckISIN(const std::string& isin)
{
  if (!CheckFormat(isin))
    return false;

  std::string coded = CodeISIN(isin);
// from http://rosettacode.org/wiki/Luhn_test_of_credit_card_numbers#C.2B.2B11
  return luhn(coded);
}


#include <iomanip>
#include <iostream>

int main()
{
  std::string isins[] = { "US0378331005", "US0373831005", "U50378331005",
              "US03378331005", "AU0000XVGZA3", "AU0000VXGZA3",
              "FR0000988040" };
  for (const auto& isin : isins)
  {
    std::cout << isin << std::boolalpha << " - " << CkeckISIN(isin) <<std::endl;
  }
  return 0;
}