Converting Decimal Numbers to Roman Numerals

Environment: C, Visual C++

The following function takes positive decimal numbers from 0–4999 and outputs them as Roman strings (for example, "MMIII" for 2003). It should compile under any version of C on any platform (although you may want to change "//" comments to the "/*...*/" form (which I hate).

I wrote the function myself, and I have no copyright concerns. I searched the CodeGuru site for "roman" and got nothing except font names, so I assume noone else has posted anything similar to this.

// written by Ste Cork, free for any and all use.
//
const char *Number_AsRomanString( int iNumber )
{
struct RomanDigit_t
  {
char *m_psString;
int m_iValue;
  };

static const RomanDigit_t RomanDigits[]=
  {
    {"M",  1000},
    {"CM",  900},
    {"D",   500},
    {"CD",  400},
    {"C",   100},
    {"XC",   90},
    {"L",    50},
    {"XL",   40},
    {"X",    10},
    {"IX",    9},
    {"V",     5},
    {"IV",    4},
    {"I",     1},
  };

// Strictly speaking, Roman digits can't display something
// such as 4999 without using overlaid bars and so forth,
// but for now this is a quick-and-dirty piece of code that'll
// just keep using M's...
//
static char sRomanString[20];
sRomanString[0] = '\0';

for (int i=0; iNumber && i<sizeof(RomanDigits)/
                           sizeof(RomanDigits[0]); i++)
  {
while ( RomanDigits[i].m_iValue <= iNumber )
    {
strcat( sRomanString, RomanDigits[i].m_psString );
iNumber -= RomanDigits[i].m_iValue;
    }
  }

return sRomanString;
}


Comments

  • *why* do people use roman numerals?

    Posted by Legacy on 07/29/2003 12:00am

    Originally posted by: njkayaker


    The roman empire is dead! Get over it.

    I really think roman numerals is something that should go away.

    Reply
  • Nice try.

    Posted by Legacy on 07/29/2003 12:00am

    Originally posted by: felix

    You only solved half of the problem. How about converting a roman numeral to a long? problem is starting to get a little harder now isn't it.

    Also, using your scheme, one million is basically 1000 M's.

    I realize that you do not support the *bar* notation, but it would have to be taken into account so that you solution could be useful.

    I would use long instead of int.


    -f

    Reply
Leave a Comment
  • Your email address will not be published. All fields are required.

Top White Papers and Webcasts

  • Companies undertaking an IT project need to find the right balance between cost and functionality. It's important to start by determining whether to build a solution from scratch, buy an out-of-the-box solution, or a combination of both. In reality, most projects will require some system tailoring to meet business requirements. Decision-makers must understand how much software development is enough and craft a detailed implementation plan to ensure the project's success. This white paper examines the different …

  • On-demand Event Event Date: February 12, 2015 The evolution of systems engineering with the SysML modeling language has resulted in improved requirements specification, better architectural definition, and better hand-off to downstream engineering. Agile methods have proven successful in the software domain, but how can these methods be applied to systems engineering? Check out this webcast and join Bruce Powel Douglass, author of Real-Time Agility, as he discusses how agile methods have had a tremendous …

Most Popular Programming Stories

More for Developers

RSS Feeds

Thanks for your registration, follow us on our social networks to keep up-to-date