Header file for isdigit

This is a discussion on Header file for isdigit within the C++ Programming forums, part of the General Programming Boards category; Does anyone know the header file to include for isdigit and isalpha?...

  1. #1
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    Question Header file for isdigit

    Does anyone know the header file to include for isdigit and isalpha?

  2. #2
    Blank
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    ctype.h

  3. #3
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    What does isdigit do
    I am a C++ newb
    using: Visual C++ 6.0
    thanx for any Help

  4. #4
    _B-L-U-E_ Betazep's Avatar
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    Code:
    # include<iostream>
    using namespace std;
    
    int main ()
    {
    
    	char number = '1';
    
    	if (isdigit(number))
               cout << "Yes " << endl;
    
    
    return 0;
    }

    compile this
    Last edited by Betazep; 12-18-2001 at 12:00 AM.
    Blue

  5. #5
    _B-L-U-E_ Betazep's Avatar
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    isdigit can be found in iostream as well...

    Imagine in the above program if the character held in 'number' was an 'a'.

    Would "Yes " still be outputted to the screen. Well no... 'a' isn't a digit. '1' is a digit.

    Pretty straightforward...
    Blue

  6. #6
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    Basically how it's done:

    Code:
    bool isdigit(char c)
    {
            if(c >= '0' && c <= '9')
                     return true;
    
            return false;
    }
    Or, even more compactly, you could make a macro:

    Code:
    #define isdigit(c) ((c >= '0' && c <= '9') ? true : false)
    That's all there is to it

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