ensure input is only integer

This is a discussion on ensure input is only integer within the C++ Programming forums, part of the General Programming Boards category; Good day, I was writing a program in C++.I was validating to ensure that only integer is accepted. that is ...

  1. #1
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    ensure input is only integer

    Good day, I was writing a program in C++.I was validating to ensure that only integer is accepted.

    that is for int a;
    a can take the value of single digit or double digit numbers like (13/123213/2312321).

    Is there any way to check,that FOR variable a,
    ONLY digits are entered and
    NO decimal(like 2.4 1.002) or characted has been inputed?

  2. #2
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    I'd say you want to grab your input with getine(), which will effectively put the number into a string. Using that you can check for decimals, and then use a stringstream to convert the string back into a number.

    If the stringstream conversion fails, what the user entered was probably not a number.

  3. #3
    Registered User Noir's Avatar
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    Why not just use cin and check if it failed to read an int?
    Code:
    int a;
    
    if ( cin >> a ) {
      // it read an int
    } else {
      // not an int
    }
    You can put all of that in a loop:
    Code:
    cout << "enter an integer> ";
    
    while ( !( cin >> a ) ) {
      cin.clear();
      cin.ignore( 256, '\n' );
      cout << "not an integer; try again> ";
    }

  4. #4
    and the hat of int overfl Salem's Avatar
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    Does numeric overflow count as a 'problem' as well for your input ?
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
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