Thread: Write a password prompt that gives a user only a certain attemts

Compare your for loop version with your while loop version and you should discover the mistake. If you still cannot see it, then show us the version with the while loop that works. If you have not written such a while loop version, then write it, since you appear so confident of getting it right that perhaps you will be able to focus on the logic and not get distracted by the syntax, hence getting it right. After that you can compare with your for loop version.

Originally Posted by amdriod

Here is my while loop version which works perfectly fine as expected:

Enter the incorrect password 5 times and you will find that it does not print "Sorry 5 Wrong attempts". The reason is that you wrote if (a=0) instead of if (a == 0).

Originally Posted by amdriod

and I've been able to make the for loop version work by modifying it a bit. But the problem remains the same. I want to figure out why didn't this code that I posted as my question work? If has the correct syntax and I'm missing logic somewhere but can't get the hand of it.

Notice that in this working for loop version, your loop condition is t>0 and you wrote t--. In your previous attempt, your loop condition was t>=5 and you wrote t++.

0 >= 5 is false, so the loop does not even run for a single iteration.

The middle expression in a for look, and the expression in a while loop both evaluate to true or false, they both will execute their blocks only if the condition evaluates to true:

Code:

    for (int n = 0; n < 5; n++); // Runs 5 times with values of n being {0,4} going in a positive direction.
    for (int n = 4; n >= 0; n--); // Runs 5 times with values of n going from 4 to 0.

With while loops a quick way to limit the iterations might be:

Code:

    int numTries = 5;
    std::string password("");

    while (n--)
    {
        password = promptUserForPassword();
        if (validatePassword(password))
        {
            break;
        }
    }

Or to really whittle it down:

Code:

    int numTries = 5;

    while (n--)
    {
        if (validatePassword(promptUserForPassword()))
        {
            break;
        }
    }

You could also selectively inject hints, based on the condition of an incorrect password:

Code:

    int numTries = 5;
    bool failedAttempt = false;
    std::string hint("Hint: My girl!"); // A real world hint! :P

    while (n--)
    {
        if (failedAttempt)
        {
            std::cout << hint << "\n";
        }
        // alternate: // std::cout << (failedAttempt ? hint + "\n" : "");

        if (validatePassword(promptUserForPassword()))
        {
            break;
        }
        // We can only get here if the password is incorrect:
        failedAttempt = true;
    }

Late edit to post above:

Where 'n' appears in the conditions of the loops I wrote, I meant to put the variable name "numTries" (which I renamed for clarity, and then forgot to update the rest of the code :S)