keyboard error handling

This is a discussion on keyboard error handling within the C++ Programming forums, part of the General Programming Boards category; I am writing a simple program for school that lets a user input a number and it tells them if ...

  1. #1
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    keyboard error handling

    I am writing a simple program for school that lets a user input a number and it tells them if they are too high or too low. But I going to be tested for all situations, including the user entering an invalid key. I was wondering if there was any way that you could handle the user pressing a letter on the keyboard. I'm new to this so any help would be greatly appreciated. Thank you.

  2. #2
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    There are several different ways. One is to use the fail(), clear(), ignore() members of the istream class. Another is to accept input into a string, validate the string, then convert the string to desired type. There may be others as well.

  3. #3
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    I would opt for the latter option. It could be done somewhat like this:
    Code:
    bool ok = true;
    string input;
    getline(cin, input);
    
    for(int i = 0; i < input.size(); ++i)
        if((input[i] - '0') > 9)
            ok = false;
    
    if(!ok)
        cout << "Failed";
    
    // other code...

  4. #4
    VA National Guard The Brain's Avatar
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    I would like to recommend the isdigit( ) function of the <cctype> library. It is a boolean function that will return true if the argument is a number.
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    Well I thought it wasn't standard..

  6. #6
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    isdigit() returns a non-zero value when the input parameter is a numberic digit, not true. But the point is still the same. And it is standard.

  7. #7
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    to tilex... would i put that as just its own separate block of code in int main() ?

  8. #8
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    You should be able to figure that on your own, I've already said more than I should have. Study the code and then when you know what it does, you'll know where it goes.

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