isdigit function help!!

This is a discussion on isdigit function help!! within the C++ Programming forums, part of the General Programming Boards category; I read that isdigit() fn returns a non-zero number, if its argument is a digit(0 to 9) and it returns ...

  1. #1
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    isdigit function help!!

    I read that isdigit() fn returns a non-zero number, if its argument is a digit(0 to 9) and it returns zero otherwise.....

    but consider the program.....
    Code:
    #include<iostream>
    #include<ctype>
    int main()
    {
    
             int c=3;
             if(isdigit(c))
             {
                    cout<<"good";
             }
             else
             {
                    cout<<"bad";
             }
    }
    The output comes as bad
    why? please help.......

  2. #2
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    sorry . . . i forgot to type "return 0;" there .... now please help.....

  3. #3
    the hat of redundancy hat nvoigt's Avatar
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    Hannover, Germany
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    You need to pass in a character to check if it is a digit (for example '9' is a digit, 'Z' is not).
    hth
    -nv

    She was so Blonde, she spent 20 minutes looking at the orange juice can because it said "Concentrate."

    When in doubt, read the FAQ.
    Then ask a smart question.

  4. #4
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    Yes, isdigit works only for char types. You declared your variable as integer. The ctype.h functions refer to chars only.

  5. #5
    Master Apprentice phantomotap's Avatar
    Join Date
    Jan 2008
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    4,231
    O_o

    The inherited `std::isdigit' works with `int'.

    nvoigt has it right. There is a difference between an integer variable with the integer value of `3' and the "ASCII" character value representing`3'.

    Code:
    int three = 3;
    Code:
    int three = '3'; // correct
    Soma

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