Inifinite loop problem (easy question)

Hey all, sorry for all the beginner's questions :(

Anyways, I'm trying to build a simple loop that will protect against unwanted input (i.e. when the user enters a characters instead of an integer). Here's what I have so far:

Code:

---

#include <iostream>
#include <cctype>

using namespace std;

int main()
{
   
    cout << "Enter a number: ";
    int number;
    cin >> number;
 
   
    while (!isdigit(number))        //Created an infinite loop!
    {cout << endl << "That is not a number, please try again: ";
    cin >> number;}
   
    cout << endl << "Enter a character: ";
    char ch;
    cin >> ch;
   
    cout << endl << number << " " << ch;
   
    int wait;
    cin >> wait;
    return 0;
}

---

First of all, am I correct that (!isdigit(number)) is really saying "Do this while the input is not an integer?"

Whenever I input a numeric value, say 3, I get the message stating "That is not a number, please try again"??!

Whenever I input a character value, I get an infinite loop stating" "That is not a number, please try again", and the program ignores the cin >> number within the loop.

Can anyone tell me whats wrong here?

Thanks.

Be careful. 2484 is an integer, but not a digit. I have no time to check it, sorry.

PD: You can read a char* and then check if num[i] is a digit.

Hmmm...nevermind, this appears to be a character function. Not an integer function. I'll have to come up with a different way to do this :)

Hi
I think you should declare the "number" variable as char. I don know why. In another way, I would like to advise you some method to check the number which is atoi. It return 0 if the input cannot be converted to a value of that type.

correct me if t wrong
thx

Sunton

Yeah, I think that solution works. I'll just have to remember not to use the variable as an INT later on.

Thanks :)

do this:

Code:

---

#include <iostream>
#include <cctype>

using namespace std;

int main()
{
int number;
  while(true)
{
    cout << "Enter a number: ";
    string numberS;
    cin >> numberS;
  number = atoi(numberS.c_str());
    if (itisanumber(numberS))
      break;
    else
    cout << "\nThat is not a number, please try again: ";

}
   
    cout << endl << "Enter a character: ";
    char ch;
    cin >> ch;
   
    cout << endl << number << " " << ch;
   
    int wait;
    cin >> wait;
    return 0;
}

---

itisanumber() function you write yourself to check if the string is a number.

Thanks for the help everyone. I was able to find fix to the problem by using cin.clear and cin.get() to clean up my input. Here's a slightly modified version of the program:

Code:

---

#include <iostream>
#include <cctype>

using namespace std;

int main()
{
   
    cout << "Enter a number (or enter 77 to exit): ";  //"Lost" reference
    int number=0;
    int sum=0;
   
 
   
    while (number!=77)
{
    if (!(cin >> number))
   
    {  cout << "That is not a number. Please enter a number: ";
        cin.clear();                                  // Resets cin error flag
        cin.get();                                    // Removes bad input       
    }
   
    else if (number==77)
    break;
   
    else
   
    {   
            sum+=number;
            cout << endl << "Enter another number: ";
    }
}

    cout << endl << "Total is: " << sum;
   
    int wait;
    cin >> wait;
    return 0;
}

---