Thread: Clearing unexpected values out of cin

  1. #1
    Registered User IdioticCreation's Avatar
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    Clearing unexpected values out of cin

    My program expects 3 numbers entered by the user. Currently if the user enters 4, or more numbers the program will still run, but the extra value will carry over later on. I would like to know if there is a standard way of clearing cin.

    Is this what cin.get() is for, I couldn't find a satisfying explanation.

    Thank you,

  2. #2
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    Jan 2005
    The standard way to clear cin is
    std::cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
    You have to #include <limits> and <ios> for numeric_limits and streamsize. This should work well if you are using operator>> to read in your numbers, since it will not cause any issues on valid input either.

    Another option is to use getline to read into a string, then place the contents of that string into a stringstream and get the numbers out of there. Anything leftover in the stringstream will just not be processed. This has the added benefit of keeping cin from entering a fail state if the user enters bad data (like non-numeric characters), since getline accepts all characters. However, you can also just add similar code to handle that situation directly with cin.

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