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This is a discussion on Help within the C++ Programming forums, part of the General Programming Boards category; How can i test data input and correct it if need be, such as if someone put a o instead ...

  1. #1
    Registered User
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    Aug 2010
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    Help

    How can i test data input and correct it if need be, such as if someone put a o instead of 0 or it has a raised digit like * instead of 8

  2. #2
    Registered User rogster001's Avatar
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    Liverpool UK
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    What did you think of? Why think of the problem like this anyway? Incorrect input is incorrect however you look at it, the fact that if somebody puts an * instead of an 8 means they accidentally depressed the shift key at the same time as keying the 8 is a moot point, it should just be filtered like any input error.
    The key combos can differ quite widely anyhow depending on local settings, like USA keyboard versus UK etc etc,
    Do you just mean you want to put clever error messages like "oops did you press the shift key also"??
    i wouldn't bother, just output 'YA DUN TYPED WRONG PARD!' and make them do it again, and again, till they can get it RIGHT! :->



    You can find a lot of help on validating input in the 'how do i..?' sections on the home pages'
    Last edited by rogster001; 09-21-2010 at 09:57 AM.
    Thought for the day:
    "Are you sure your sanity chip is fully screwed in sir?" (Kryten)
    FLTK: "The most fun you can have with your clothes on."

    Stroustrup:
    "If I had thought of it and had some marketing sense every computer and just about any gadget would have had a little 'C++ Inside' sticker on it'"

  3. #3
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    Sep 2010
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    33
    You can mess around with strings and things.

    I like this method but I donít know if this is good or bad practise.

    Code:
    #include <iostream>
    #include <string>
    #include <sstream>
    using namespace std;
    
    int main(){
    
    string str_input;
    float weight;
    
    bool err = true;
    while (err == true ){
        err = false;
    
        cout << "Enter weight in Kg's, zzz.zz : ";
        getline (cin, str_input);
            
        for (int i = 0; i < str_input.length(); i++)
            if (!(isdigit(str_input[i]) || str_input[i] == '.'))
                // Only 0-9 or '.' allowed
                err = true;
        
        if (str_input.length() > 6)
            // Max 6 chars allowed
            err = true; 
            
        int ndp = str_input.find('.');
        if (ndp != string::npos)
            if (str_input.find('.', ndp+1) != string::npos)
                //Only 1 decimal point allowed
                err = true;  
            else
                if (ndp > 3)
                    // Max 3 leading chars allowed
                    err = true;
                else
                {
                    string dp = str_input.substr(str_input.find(".") +1);
                    if (dp.length() > 2)
                        // Max 2 dec places allowed
                        err = true;
                }
                
        if (err == true)
            cout << "*Invalid format, must be 0-9 in format zzz.zz*" << endl;
    
    }// end while loop
    
    // Convert input string to float
    istringstream ins;
    ins.str(str_input);
    ins >> weight;
    
    cout << "Produce weighs " << weight << " Kg's" << endl;
    
    system ("pause"); // temp to stop console closing
    return 0;
    }

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