My function skips a loop parameter in c++ - c++

Question

My GetMark() function, which is supposed to check for correct range and afterwards return the value, if correct to the given array gets stuck in a infinite loop when a parameter is given outside of the accepted range, before i added the SearchMark() function it worked correctly and looped only until the user finally entered a value in the given range (0 - 100) but now after the first out of range value is given it loops no matter what is entered, I will be thankful for any suggestions. full code:
int GetMark(int ModuleIndex) //user input function
{
bool help;
if (ModuleIndex < 0 || ModuleIndex >100)
{
help = false;
while (help != true)
{
cin.clear();
cin.ignore(numeric_limits<streamsize>::max(), '\n');
cout << "hey, that's a invalid value, try again!" << endl;
GetMark(ModuleIndex);
if ((ModuleIndex > 0) &&( ModuleIndex < 101))
{
help = true;
}
}
}
return ModuleIndex;
}
int SearchMark(int A[], int a) //search grades array for numbers of specific grades
{
int i = 0;
int ii = 0;
while (i < 12)
{
if (A[i] == a)
ii++;
i++;
}
cout << "Mark " << a << " was found: " << ii << " times" << endl;
return 0;
}
int main()
{
int marks[12];
int i = 0;
int sum = 0;
int grades[12];
while (i < 12)
{
cout << "enter mark (0 - 100): " << endl;
cin >> marks[i];
GetMark(marks[i]);
sum = sum + marks[i];
if (marks[i] > 69)
{
grades[i] = 1;
}
else if (marks[i] > 59 && marks[i] < 70)
{
grades[i] = 2;
}
else if (marks[i] > 49 && marks[i] < 60)
{
grades[i] = 22;
}
else if (marks[i] > 39 && marks[i < 50])
{
grades[i] = 3;
}
else if (marks[i] < 35)
{
grades[i] = 4;
}
i++;
}
sum = sum / 12;
cout << "your average is: " << sum << endl;
if (sum > 69)
{
cout << "You passed with 1st!" << endl;
}
else if ((sum > 59) && (sum < 70))
{
cout << "You passed with 2i!" << endl;
}
else if ((sum > 49) && (sum < 60))
{
cout << "You passed with 2ii!" << endl;
}
else if ((sum > 39) && (sum < 50))
{
cout << "You passed with 3rd!" << endl;
}
else if (sum < 40)
{
cout << "Your average is too low! You failed." << endl;
}
i = 0;
while (i < 12)
{
if (marks[i] < 35)
{
cout << "Referred in module " << i + 1 << " mark too low." << endl;
}
i++;
}
SearchMark(grades, 1);
SearchMark(grades, 2);
SearchMark(grades, 22);
SearchMark(grades, 3);
SearchMark(grades, 4);
return 0;
}`

Answer 1

That function is overly complicated for what it does. Just loop while the value is bad, and prompt for a new value:
int GetMark(int ModuleIndex) {
while (ModuleIndex < 0 || ModuleIndex > 100) {
std::cout << "Invalid value.\n"
std::cin >> ModuleIndex;
}
return ModuleIndex;
}
Recursion is very handy in theoretical analysis, but in practice it's almost always a mistake.

Answer 2

You need to allow the user to specify a new value of marks[i] / ModuleIndex within GetMarks. After clearing cin, read a new value from cin. You also need to return that value so that main's marks[i] can be updated with that value instead of the original out-of-range value.

Answer 3

Basically what you need to do is remove the recursion from this method and just rely on the while loop. Instead of recalling the function you need to prompt for input again with the failed input and then test the value again to escape the loop.
int GetMark(int ModuleIndex) //user input function
{
bool help;
if (ModuleIndex < 0 || ModuleIndex >100)
{
help = false;
while (help != true)
{
cin.clear();
cin.ignore(numeric_limits<streamsize>::max(), '\n');
cout << "hey, that's a invalid value, try again!" << endl;
cout << "enter mark (0 - 100): " << endl;
cin >> ModuleIndex;
if ((ModuleIndex > 0) &&( ModuleIndex < 101))
{
help = true;
}
}
}
return ModuleIndex;
}

Answer 4

It is apparently in you getMark, inside the while loop you are calling getMark recursively with the same invalid ModuleIndex value. So you need to get it from the standard input before recursion. e.g:
int GetMark(int ModuleIndex){
bool help;
if (ModuleIndex < 0 || ModuleIndex > 100){
help = false;
while (help != true){
cout << "enter new ModuleIndex: \n";
cin >> ModuleIndex;
GetMark(ModuleIndex);
// ...
}
return ModuleIndex;
}
Your code is unreadable, in addition you can use class std::vector.
I propose to test this code:
int GetMarkIndex(const std::vector<double>& vMarks, const double Search) {
auto beg{ vMarks.begin() }, end{ vMarks.end() };
while (beg != end && *beg != Search)
++beg;
return beg != end ? beg - vMarks.begin() : -1;
}
int main() {
std::vector<double> marks(5);
int value;
auto i{ 0U };
auto sz{ marks.size() };
while (i != sz) {
std::cout << "Enter marks 1-->100" << std::endl;
if (cin >> value && value > 0 && value < 101) {
marks[i] = value;
++i;
}
else
std::cout << "Invalid input!" << std::endl;
}
for (auto e : marks)
cout << e << ", ";
std::cout << std::endl;
double Search = 15;
auto index{GetMarkIndex(marks, Search)};
(index != -1) ? (std::cout << Search << " Found at index: " << index) : (std::cout << Search << " Not found!" << std::endl);
std::cout << std::endl;
}

Answer 5

The combination of the way you have defined GetMark and the way you use it is flawed.
No matter what you do in GetMark, the value entered in main does not change.
Change GetMark to:
int GetMark()
{
std::cout << "enter mark (0 - 100): " << std::endl;
int mark;
while ( std::cin >> mark )
{
if ( mark >= 0 && mark <= 100)
{
return mark;
}
std::cout << "Invalid value " << mark << std::endl;
std::cout << "enter mark (0 - 100): " << std::endl;
}
// Unable to read.
// Throw exception, or exit with an error message.
}
and change its usage. Instead of
cout << "enter mark (0 - 100): " << endl;
cin >> marks[i];
GetMark(marks[i]);
use
marks[i] = GetMark();
A working version of GetMark:
int GetMark()
{
std::cout << "enter mark (0 - 100): " << std::endl;
std::string line;
while ( getline(std::cin, line) )
{
std::istringstream str(line);
int mark;
if ( str >> mark )
{
if ( mark >= 0 && mark <= 100)
{
return mark;
}
}
std::cout << "Invalid input: " << line << std::endl;
std::cout << "enter mark (0 - 100): " << std::endl;
}
// Unable to read.
// Throw exception, or exit with an error message.
return 0;
}
Live Demo.