How to get my program to read thru errors - c++

Question

I have an assignment for school in which the goal is to read data from a text file, and output calculations made with the info. I've gotten the inputing and outputting mostly down, but our prof wants us to include error checking aswell. I've done error checking for strings, and now im working on ints/doubles. The only issue is when i try to use the sample error input file he provided, my while loop dosen't fire at all.
bool isWord(string s)
{
for (int i = 0; i < s.length(); ++i)
{
if (::isdigit(s[i])){
return false;
}
}
return true;
}
int main()
{
ifstream inData;
ofstream outData;
inData.open("inData.txt");
outData.open("outData.txt");
//check for Error
if (inData.fail()){
cout << "Error opening file!" << endl;
exit(1);
}
if (outData.fail()){
cout << "Error opening file!" << endl;
exit(1);
}
double rWidth;
double rLength;
double cRad;
double number = 0;
string fName;
string lName;
string word;
int age;
int i = 0;
int savings;
int count = 0;
int people = 0;
int tAge = 0;
int tSavings = 0;
string names[256];
double tLength = 0;
double tWidth = 0;
double tArea = 0;
double perimeter = 0;
double tRad = 0;
double tCarea = 0;
double tCirc = 0;
while(inData >> rWidth >> rLength >> cRad >> fName >> lName >> age >> savings){
cout << rWidth << " " << rLength << " " << cRad << " " << fName << " " << lName << " " << age << " " << savings << "\n";
stringstream fNameStream(fName);
stringstream lNameStream(lName);
while (fNameStream >> word)
{
if (isWord(fName))
{
names[count++] = word;
}
else
{
names[count++] = "John";
}
}
while (lNameStream >> word)
{
if (isWord(lName))
{
names[count++] = word;
}
else
{
names[count++] = "Doe";
}
}
istringstream widthStream(rWidth);
while (widthStream >> number)
{
if (widthStream >> number)
{
widthStream >> rWidth;
}
else
{
rWidth = 0.0;
}
}
tLength = tLength + rLength;
tWidth = tWidth + rWidth;
perimeter = perimeter + (2*(rWidth+rLength));
tArea = tArea + (rWidth*rLength);
tRad = tRad + cRad;
tCarea = tCarea + pow(cRad, 2) * M_PI;
tCirc = tCirc + (2*M_PI*cRad);
tAge = tAge + age;
tSavings = tSavings + savings;
}
cout << tLength << "\n";
cout << tWidth << "\n";
cout << perimeter << "\n";
cout << tArea << "\n";
cout << tCarea << "\n";
cout << tCirc << "\n";
cout << tAge << "\n";
cout << tSavings < "\n";
cout << count << "\n";
while (i < count)
{
cout << names[i] << " ";
i++;
}
outData << "Rectangle: \n";
outData << "The total length= " << tLength << ", width= " << tWidth << ", area= " << tArea << "\n";
outData << "Perimeter= " << perimeter << "\n\n";
outData << "Circle:\n";
outData << "The total radius= " << tRad << ", area= " << tCarea << ", circumference= " << tCirc << "\n\n";
outData << "People:\n" << "Total number of people= " << count << "\n" << "Total Age= " << tAge << "\nTotal Savings= " << tSavings;
inData.close();
outData.close();
system("pause");
return 0;
}
Hopfully thats formatted correctly.
The program runs fine and dandy when i use:
10.45 8.76
13.78
Jake Melon 45
7600
128 76.9
11
Mike Sander 56
800
15.9 43
6400
David James 32
87000.54
But when i use:
10.45 aaaa
13.78
Jake Melon 45
7600
128 76.9
;
Mike Sander 23
800
15.9 43
w
David James i
87000.54
My main while loop (where I read data) doesn't fire for some reason, and all of my values remain at 0. Your help will be greatly appreciated! And I'm sorry for such a long block of text.

Answer 1

Error recovery is difficult and there are no standard methods (think about how your compiler recovers from a syntax error).
You will need an outer loop for your while loop. You'll want to come up with a design that will help you resynchronize on the input format. Again, not an easy task.
A simple method is to count the text lines and display the text line where the failure existed and end the program. From that you can display more information, such as the field that was in error. Some programmers assume the worst that once an error is found the remaining data can't be trusted.
I recommend putting in place a simple error announcement and safely terminate (clean up, flush to disk, etc.). Work on getting the remainder of your program working correctly, then come up with better error handling strategies.