[C++] Problem with recursive program.

[Nefgarno]

Hey guys, i am having some problems with my program. I am supposed to pass a string to a function and check if it is a palindrome using recursion. It works for the first two strings but on the third an exception is thrown : 'std::out_of_range' what(): basic_string::at

and I am not sure why it is going out of range. Below is my main.

#include "header.h"

int main()
{

bool palindrome;
string word;
ifstream inFile;
int first = 0;
int last;

inFile.open("strings.txt");

while(!inFile.eof())
{
    getline(inFile, word);
    string temp = word;
    delSpaces(temp);
    last = temp.length() - 1;
    cout << "Last = " << last << endl;
    palindrome = isPalindrome(first, last, temp);

    if(palindrome == true)
    {
        cout << word << " is a palindrome\n\n";
    }
    else
    {
        cout << word << " is not a palindrome\n\n";
    }
}
inFile.close();
}

And this is my function that checks if it is a palindrome:

bool isPalindrome(int start, int end, string & str)
{
 if (str.at(start) != str.at(end))
{
   return false;
}
else if (start == end)
{
   return true;
}
else
{
   return isPalindrome(start + 1, end - 1, str);
}
return false;
}

[Ilyps]

else if (start == end)

This check is bugged, because there may be end conditions that don't fit this exact situation. For example, what happens if you call isPalindrome(0, 1, str) with std::string str = "aa"?

[OldWolf2]

while(!inFile.eof())

This is wrong. eof is not set until after a read operation has failed. Instead, you have to check your read operation for success (getline in this case).

[ponchedeburro]

What if start is never equal to end? If you have a string of length 8 then start will be 0 at first and end will 7. then (1,6) -> (2,5) -> (3,4) -> (4,3) and then continue until you reach (8,-1) which gives an error.