Roman Numeral Help

[quietpupil]

I need to be able to sum Roman numerals in the most simple way, not necessarily proper numerals. Somebody please tell me what I'm doing wrong.

#include <iostream>
using namespace std;

int main()
{
{
int M = 1000;
int D = 500;
int C = 100;
int L = 50;
int X = 10;
int V = 5;
int I = 1;
}

{
const int A_ROMAN = 50;
int sum[A_ROMAN];
cout << "Enter your first Roman Numeral";
cin >> [A_ROMAN];
{
for (int a = 0; a < 5; a++)
{
sum += A_ROMAN[a];
}
}
}
{
const int B_ROMAN = 50;
int sum[B_ROMAN];
cout << "Enter your second Roman Numeral";
cin >> B_ROMAN[b];
{
for (int b = 0; b < 5; b++)
{
sum += B_ROMAN[b];
}
}
}
}

[cire]

I think you'll find that adding numbers in a roman numeral representation is a relatively complex operation. You'll find it easier to convert to a regular number, add and convert back to roman numerals.

[quietpupil]

Does this work at all?
#include <iostream>
using namespace std;

int main
{
switch (ROMAN_NUM)
{
case 'M': 1000;
case 'D': 500;
case 'C': 100;
case 'L': 50;
case 'X': 10;
case 'V': 5;
case 'I': 1;
}
const int A_ROMAN = 50
int sum[A_ROMAN];
cout << "Enter the first Roman numeral.";
cin >> [A_ROMAN];
{
for (int a = 0; a < A_ROMAN; a++)
total += A_ROMAN[a];
}
cout << "The decimal of the first Roman numeral is" << total << endl;

}

[Duthomhas]

It doesn't even compile.

To convert Roman→decimal, I recommend the following approach:

For each 'match', first-to-last in the following list, left-to-right in the roman numeral string, add the associated value:

    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

The first tricky part is the order that you do things, which must be exact.

The other tricky part is, of course, that a match may be more than one letter. So, for example

    MCMLXXIV

matches as

    M   CM   L   X   X   IV

which is the sum:

    1000 + 900 + 50 + 10 + 10 + 4

or 1974.

When you are ready to convert back, you use the table above, but work with the arrows pointing in the other direction. So

    1974 - 1000 (M)  = 974
     974 -  900 (CM) = 74
      74 -   50 (L)  = 24
      24 -   10 (X)  = 14
      14 -   10 (X)  = 4
       4 -    4 (IV) = 0

giving you MCMLXXIV.

Oh, and 0 is "N" or "NULLA" in Roman numerals. You'll need a special case to check for that.

Hope this helps.