Task

Create a function taking a positive integer as its parameter and returning a string containing the Roman numeral representation of that integer. Modern Roman numerals are written by expressing each digit separately, starting with the left most digit and skipping any digit with a value of zero.



In Roman numerals:

 1990 is rendered: 1000=M, 900=CM, 90=XC; resulting in MCMXC
 2008 is written as 2000=MM, 8=VIII; or MMVIII
 1666 uses each Roman symbol in descending order: MDCLXVI


#include <iostream>
#include <string>
 
std::string to_roman(int value)
{
  struct romandata_t { int value; char const* numeral; };
  static romandata_t const romandata[] =
     { 1000, "M",
        900, "CM",
        500, "D",
        400, "CD",
        100, "C",
         90, "XC",
         50, "L",
         40, "XL",
         10, "X",
          9, "IX",
          5, "V",
          4, "IV",
          1, "I",
          0, NULL }; // end marker
 
  std::string result;
  for (romandata_t const* current = romandata; current->value > 0; ++current)
  {
    while (value >= current->value)
    {
      result += current->numeral;
      value  -= current->value;
    }
  }
  return result;
}
 
int main()
{
  for (int i = 1; i <= 4000; ++i)
  {
    std::cout << to_roman(i) << std::endl;
  }
}