Checking Errors of Roman Numerals Given A Set of Rules

Question

So for my comp sci class I was tasked with adding, subtracting, dividing, and multiplying Roman Numerals if they pass 12 rules that I have been given.

I created a 13 element boolean array to keep track of which rules were broken. I created a function called checkErrors, which calls each of the 12 rule checking functions. I call the checkErrors to check each roman numeral before the calculation is done and print out which of the errors is wrong (if any) but instead of just printing out the ones that are wrong it prints each one.

Below is a snippet from checkErrors which is the same for each rule (checkErrorOne, checkErrorTwo...etc.). If the rule is broken, errors[0] is set to false to show that the whole roman numeral is not legal.

`bool checkErrors(string romanNumeral, bool * errors) {
if (checkErrorOne(romanNumeral) == false) {
    errors[1] = false;
    errors[0] = false;
}
if (checkErrorTwo(romanNumeral) == false) {
    errors[2] = false;
    errors[0] = false;
}
if (checkErrorThree(romanNumeral) == false) {
    errors[3] = false;
    errors[0] = false;
}
if (checkErrorFour(romanNumeral) == false) {
    errors[4] = false;
    errors[0] = false;
}
if (checkErrorFive(romanNumeral) == false) {
    errors[5] = false;
    errors[0] = false;
}
if (checkErrorSix(romanNumeral) == false) {
    errors[6] = false;
    errors[0] = false;
}
if (checkErrorSeven(romanNumeral) == false) {
    errors[7] = false;
    errors[0] = false;
}
if (checkErrorEight(romanNumeral) == false) {
    errors[8] = false;
    errors[0] = false;
}
if (checkErrorNine(romanNumeral) == false) {
    errors[9] = false;
    errors[0] = false;
}
if (checkErrorTen(romanNumeral) == false) {
    errors[10] = false;
    errors[0] = false;
}
if (checkErrorEleven(romanNumeral) == false) {
    errors[11] = false;
    errors[0] = false;
}
if (checkErrorTwelve(romanNumeral) == false) {
    errors[12] = false;
    errors[0] = false;
}

if (errors[0] == true)
    return true;
else if (errors[0] == false)
    return false;

} `

to return the value of the first element to say if it is legal.

After this when I go to print each rule that was broken I use the following:

void printFunction(string romanNumeral1, string romanNumeral2, string mathOperator, bool errors[]){
if (checkErrors(romanNumeral1, errors) == false && checkErrors(romanNumeral2, errors) == true){

    cout << romanNumeral1 << " is illegal becasue" << endl;
    if (errors[1] == false)
        cout << "Contains a letter that is not M, D, C, L, X, V, or I;" << endl;
    if (errors[2] == false)
        cout << "I is not followed by I, V, or X;" << endl;
    if (errors[3] == false)
        cout << "X is not followed by I, V, X, L, or C;" << endl;

for each of the 12 rules. It is printing out every one of the errors, not each one that is wrong.

If someone could help with my logic it would be greatly appreciated.

void printFunction(string romanNumeral1, string romanNumeral2, string mathOperator, bool errors[]){
if (checkErrors(romanNumeral1, errors) == false && checkErrors(romanNumeral2, errors) == true){

    cout << romanNumeral1 << " is illegal becasue" << endl;
    if (errors[1] == false)
        cout << "Contains a letter that is not M, D, C, L, X, V, or I;" << endl;
    if (errors[2] == false)
        cout << "I is not followed by I, V, or X;" << endl;
    if (errors[3] == false)
        cout << "X is not followed by I, V, X, L, or C;" << endl;

Edit: Why does the code I wrote print out each of the 12 errors I created instead of only printing out the ones that were violated?

Thanks

If you could help by using a debugger, it would be greatly appreciated. Execute your program statement by statement, *watching* the values of variables. Let us know which statement is causing the issue. — Thomas Matthews, Apr 29 '16 at 19:34
What is the value of the `errors` array when everything is printed? — Thomas Matthews, Apr 29 '16 at 19:38
I suggest you change your logic so that `errors[X]` is set to `true` if there is an error. Initialize all slots to `false` before the validation. — Thomas Matthews, Apr 29 '16 at 19:47
All but the first one are 0. It is 1. The first one should be set to 0 if one of the other `errors` is set to 1, but it is still set to 1 when none of the others are. — Zack Sloan, Apr 29 '16 at 19:49
What is the meaning when `checkErrorOne` returns false? Does it mean there is an error or not? — Thomas Matthews, Apr 29 '16 at 19:53
Yes it returns false if the error is violated. Sorry for no comments in the code — Zack Sloan, Apr 29 '16 at 20:01

score 3 · Accepted Answer · answered Apr 29 '16 at 19:45

3

Off-topic: Your program can be simplified by having an array of error messages.

The if statement ladder would be replaced by a loop:

for (unsigned int i = 0U; i < MAXIMUM_ERROR_TYPES; ++i)
{
  if (errors[i])
  {
    std::cout << error_messages[i];
  }
}

Since there is less code, there will be less possibility of injected defects.

answered Apr 29 '16 at 19:45

Thomas Matthews

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awesome. will implement that later tonight when I get back to my computer. – Zack Sloan Apr 29 '16 at 20:02
If this was helpful, please click on the check mark. – Thomas Matthews Apr 29 '16 at 20:05

score 0 · Answer 2 · answered Apr 29 '16 at 19:30

Ok, first of all, you didn't post your checkErrors code, so i am assuming here. I think that you defined is as

bool checkErrors(string, bool errors[13]){

which means, that it does not take a pointer, but a copy of the 13 booleans. So they get modified within your function, but not outside it. Change it to:

bool checkErrors(string, bool* errors){

ps. Next time, please think about how people with no knowledge about your poblem will understand it. Saves you a lot of flak ;)

Added the whole code for check errors with the change you suggested — Zack Sloan, Apr 29 '16 at 19:37

Checking Errors of Roman Numerals Given A Set of Rules

2 Answers2