Catching bad input

This is a discussion on Catching bad input within the C++ Programming forums, part of the General Programming Boards category; Is there a simple way of catching bad input for integers? Say if someone enters a character instead?...

  1. #1
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    Catching bad input

    Is there a simple way of catching bad input for integers? Say if someone enters a character instead?

  2. #2
    PC Fixer-Upper Waldo2k2's Avatar
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    One way (how i do it) is to come up with something like this:
    Code:
    int main() {
    //make an int array
    //if you're reading INTEGER from cin(), you must give it a size first 
    //to avoid compiling errors
    int INTEGER[1000];
    //set up boolean variable for use in while loop, set it to false (0)
    bool isOK="0";
    while (isOK=="0") {
    cout<<"enter integer"<<endl;
    cin>>INTEGER;
    //now that you have it, test it for letters
    //cycle through entire alphabet based on this example
    if (INTEGER[0]=='a'||'b'||'c') {
    //since it got to here, there were letters in the variable so set
    //bool to false, which will make the loop go again and ask for 
    //INTEGER until it checks out
    isOK="0";
    }
    //repeat for INTEGER[1], etc., up to a reasonable number,
    //obviously you don't want to go to 1000 (p.s. 1000 was just 
    //an example size
    //now if you checked for all the parts of the array, time to allow
    //it to break out if there were no letters
    else{
    isOK="1";
    }
    //that will break the loop if everything was fine, repeat just as 
    //the last set of checks
    //P.S. don't forget to place the else right after the } in each 
    //if statement, otherwise it won't compile correctly
    }
    good luck, if it doesn't work....consult an expert

    [edit]changed my mind, added else statements to code to avoid too much typing, sorry i didn't think of it first, it's been a long day[/edit]
    Last edited by Waldo2k2; 05-28-2002 at 06:44 PM.
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  3. #3
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    The way i've been looking at is something similar to this:

    Code:
    float af;
    int a;
    
    cin >> af;
    a = (int) af;
    
    if (cin.fail() || (af-(float)a != 0))
    throw CWrongDataType();
    Was just wondering if there was a simpler way....

  4. #4
    PC Fixer-Upper Waldo2k2's Avatar
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    like i implied, im not an expert, im not even all the way through the book i bought ...anyhow, that looked good and would worka heck of a lot better than what i proposed, use that...
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