This program takes a roman numeral string as a command-line parameter, and outputs its value as an integer. It does not check for the validity of the roman numeral, but it does not crash (non-roman numerals are treated as zeros; values less then the highest value to values on their right are treated as subtracted values (which is correct for iv,…

(a) RomanNumeralConversion.cpp

#include <stack>
#include <string>
#include <iostream>
#include "RomanConversionTools.hpp"
using namespace std;

int main (int argv, char* argc[]) {
    // Examine arg count and exit if there's an incorrect parameter ammount
    if (argv != 2) {
        cout << "Wrong ammount of parameters" << endl;
        cout << "Usage: " << argc[0] << " <valid roman numeral>" << endl;
        return 1;
    }

    // Initalize objects and values; includes one string, stack, and two integers
    string romanNumeral;
    stack<int> romeValues;
    unsigned int lastChar;
    int lastHighValue = 0;

    // Assign the second paramter to a c++ string and record its length
    romanNumeral = argc[1];
    lastChar = romanNumeral.size();

    // Push each value (left to right) into the stack, converting each letter to an integer
    for (int i = 0; i < lastChar; ++i){
        romeValues.push(romeCharToInt(romanNumeral[i]));
    }

    // Initialize highest value variable to what's currently on the top of the stack
    lastHighValue = romeValues.top();

    // Take the top two values, add (or subtract) the second value to the top,
    // and place the top back on the stack for each char in romeCount
    for (int i = romeValues.size(); i != 1; --i) {
        romeCount(romeValues, lastHighValue);
    }

    // Output the number and pause
    cout << romanNumeral << " is equal to " << romeValues.top() << endl;
    cout << "Press enter to terminate"; cin.ignore();

}

(b) RomanConversionTools.hpp

#ifndef ROME
#include <stack>

// Takes a char and returns its magnitude if it were a roman digit
int romeCharToInt(char rome);

// Take the top two numbers, add or subtract the second value to the top,
// and place the top back onto the stack
void romeCount(std::stack<int> &romanStack, int &lastHighValue);

#define ROME
#endif

(c) RomanConversionTools.cpp

#include <stack>
using namespace std;

int romeCharToInt(char rome) {
	//--------------- V converts lower-case to upper-case
	switch (rome > 90 ? rome-32 : rome) {
	case 'I': return 1;
	case 'V': return 5;
	case 'X': return 10;
	case 'L': return 50;
	case 'C': return 100;
	case 'D': return 500;
	case 'M': return 1000;
	default: return 0;
	}
}

void romeCount(stack<int> &romanStack, int &lastHighValue) {
	int total = romanStack.top(); romanStack.pop();
	int next = romanStack.top(); romanStack.pop();
	
	if (next > lastHighValue) lastHighValue = next;
	if (next < lastHighValue) next *= -1;

	total += next;
	romanStack.push(total);
}