Input validation in do-while

Question

I'm having a problem with the input error.My input is validated but my error message "Invalid Range. Please Enter Range 0-100:" is not showing if there's invalid input.

Here's an example:

Please Enter Grade 1: 101 (It does not accept input)
Please Enter Grade 1: 321 (It does not accept input)

Instead of showing:

Please Enter Grade 1: 101 (It does not accept input)

Invalid Rage. Please Enter Range 0-100.
Please Enter Grade 1:

Here's My Code:

for(vector<double>::size_type i = 0; i < 15; i++)
  {
    do
    {
         cout << "Please Enter Grade "<< i + 1 <<": " << flush;
            cin >> gradesVector[i];
        }
        while(gradesVector[i] < 0.0 || gradesVector[i] > 100.0);
        { 
            cout << "Invalid Rage. Please Enter Range 0-100:\n";
                cout << "Please Enter Grade "<< i + 1 <<": " << flush;
                    cin >> gradesVector[i];
         }   
}

Tanuj Yadav · Accepted Answer · 2017-04-02T06:14:17.567

1

Your while() condition should be

while(gradesVector[i] < 0.0 || gradesVector[i] > 100.0) and use this code

for(vector<double>::size_type i = 0; i < 15; i++)
  {
   int c=0;
    do
    {
        if(c!=0)   //checking that we didnt entered loop for first time
          cout << "Invalid Rage. Please Enter Range 0-100:\n";         

           cout << "Please Enter Grade "<< i + 1 <<": " << flush;
           cin >> gradesVector[i];
           c++;   
     }
        while(gradesVector[i] < 0.0 || gradesVector[i] > 100.0);

}

edited Apr 02 '17 at 06:14

answered Apr 02 '17 at 06:03

Tanuj Yadav

1,259
13
21

I've tried that, but it won't output my error message "Invalid Rage. Please Enter Range 0-100: when a invalid input is entered – Tayvion Payton Apr 02 '17 at 06:07
wait a min, m updating – Tanuj Yadav Apr 02 '17 at 06:09
@TayvionPayton check it now – Tanuj Yadav Apr 02 '17 at 06:14
thanks this helped me out a lot. now i'm having a problem where if i enter a letter it automatically ends the program – Tayvion Payton Apr 02 '17 at 06:50
@TayvionPayton see this http://stackoverflow.com/questions/11523569/how-can-i-avoid-char-input-for-an-int-variable – Tanuj Yadav Apr 02 '17 at 10:42

score 1 · Answer 2 · answered Apr 02 '17 at 06:19

You are mixing a do construct with a while. Use either not both. Also your test in your while does not make sense. It can't be less and more at the same time. Edit to the following and it should work

for(vector<double>::size_type i = 0; i < 15; i++)
    {
        cout << "Please Enter Grade "<< i + 1 <<": " << flush;
        cin >> gradesVector[i];
        while(gradesVector[i] < 0.0 || gradesVector[i] > 100.0); // or not and
        { 
            cout << "Invalid Rage. Please Enter Range 0-100:\n";
                cout << "Please Enter Grade "<< i + 1 <<": " << flush;
                    cin >> gradesVector[i];
        }   
    }

MarkoPaulo · Answer 3 · 2017-04-02T06:24:26.050

1

Your while condition is not right.

std::vector<double> gradesVector;
gradesVector.reserve(15);
for (std::vector<double>::size_type i = 0; i < 15; i++)
{
    double grade;
    std::cout << "Please Enter Grade " << i + 1 << ": " << std::flush;
    std::cin >> grade;
    while (grade < 0.0 || grade > 100.0)
    {
        std::cout << "Invalid Range. Please Enter Range 0-100:\n";
        std::cin >> grade;
    }
    gradesVector.push_back(grade);
}

Also I would only add the grade to the vector once it is valid.

edited Apr 02 '17 at 06:24

answered Apr 02 '17 at 06:20

MarkoPaulo

474
4
19

This will give infinite loop when invalid input is entered – Tanuj Yadav Apr 02 '17 at 06:22
@TanujYadav, even before the edit it wasn't giving an infinite loop. – MarkoPaulo Apr 02 '17 at 06:25
it will give, because you were adding the input to the vector even if it was invalid, and then you were accessing that value only to check for valid input in further iterations – Tanuj Yadav Apr 02 '17 at 06:27
Actually my bad, it was indeed the case! – MarkoPaulo Apr 02 '17 at 06:27
Thanks alot this was the solution i needed. – Tayvion Payton Apr 02 '17 at 06:31
now i'm having a problem whenever i enter a letter it goes into a infinite loop – Tayvion Payton Apr 02 '17 at 06:35
This is now a different question, you can find a solution to your problem [here](http://stackoverflow.com/questions/10828937/how-to-make-cin-take-only-numbers) – MarkoPaulo Apr 02 '17 at 06:47

Input validation in do-while

3 Answers3