Question

Write and test a function toDecimal() that converts a roman number such as MCMLXXVII to its decimal number representation. Write a main program to test the function. Your function should have two arguments - the roman number as a string, and an error processing function. Write a helper function that will return the numeric value of each of the letters used in roman numbers. Then convert the string argument as follows look at the first two characters. If the first has a larger value than the second, then simply convert the first, call the conversation function again for the substring starting with the second character, and add both values. If the first character has a smaller value than the second, subtract the first from the second, and add the result to the conversion of the remaining string. Without validation this will convert also string that are not roman numbers, for example, "IC". Validate the string argument, if there is an error, call the error processing function passed as the second argument. Provide at least two error processing functions and test toDecimal with each of them. For example, one function may ask the user to correct the error, another may try to correct the error in some simple way, a third may just print a message and cause toDecimal to return a default value, etc..

- The symbols "I", "X", "C", and "M" can be repeated up to 3 times in succession, but no more. (They may appear more than three times if they appear non-sequentially, such as XXXIX.) "D", "L", and "V" can never be repeated.

- "I" can be subtracted from "V" and "X" only. "X" can be subtracted from "L" and "C" only. "C" can be subtracted from "D" and "M" only. "V", "L" and "D" can never be subtracted.

-Only one small value symbol may be subtracted from any large-value symbol.

please write this in C++ language

Answer 1

CODE

// Program to convert Roman Numerals to Numbers

#include<bits/stdc++.h>

using namespace std;

// This function returns value of a Roman symbol

int value(char r)

{

  if (r == 'I')

    return 1;

  if (r == 'V')

    return 5;

  if (r == 'X')

    return 10;

  if (r == 'L')

    return 50;

  if (r == 'C')

    return 100;

  if (r == 'D')

    return 500;

  if (r == 'M')

    return 1000;

  return -1;

}

// Returns decimal value of roman numaral

int toDecimal(string &str)

{

  // Initialize result

  int res = 0;

  // Traverse given input

  for (int i=0; i<str.length(); i++)

  {

    // Getting value of symbol s[i]

    int s1 = value(str[i]);

    if (i+1 < str.length())

    {

      // Getting value of symbol s[i+1]

      int s2 = value(str[i+1]);

      // Comparing both values

      if (s1 >= s2)

      {

        // Value of current symbol is greater

        // or equal to the next symbol

        res = res + s1;

      }

      else

      {

        res = res + s2 - s1;

        i++; // Value of current symbol is

          // less than the next symbol

      }

    }

    else

    {

      res = res + s1;

      i++;

    }

  }

  return res;

}

// Driver Program

int main()

{

  // Considering inputs given are valid

  string str ="MCMLXXVII";

  cout << "Integer form of Roman Numeral is "

    << toDecimal(str) << endl;

  return 0;

}