How to create a C function

This is a discussion on How to create a C function within the C Programming forums, part of the General Programming Boards category; How do I create a C function? Something so that I can define a certain word, say help, as a ...

  1. #1
    ! |-| /-\ +3 1337 Yawgmoth's Avatar
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    How to create a C function

    How do I create a C function? Something so that I can define a certain word, say help, as a function that is equivalent to:
    printf("[Help stuff here]");

  2. #2
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    Oh my...

  3. #3
    Registered User Pioneer's Avatar
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    I don't understand what you want, can you try explaining it a different way?

  4. #4
    ! |-| /-\ +3 1337 Yawgmoth's Avatar
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    You see, my problem is that I have a long bunch of code that appears repeatedly in my program. I don't want to type it over and over, and copying and pasting is too much work. So how can I make it so that I type one word instead of a whole bunch. E.g. the follwing 2 pieces of code are equivalent:

    1. calculate

    2. int x;
    printf("blahblahblah");
    int y;
    printf("blahblahblah");
    scanf("%d",x);
    printf("blahblahblah");
    scanf("%d",y);
    int z;
    z=x+y;
    printf("blahblahblah);

    So how can I do that?

  5. #5
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    You can create a function before the main function, eg

    Code:
    int calculate()
    {
       int a, b;
       /* prompt a*/
       scanf("%d", &a);
       /* prompt b */
       scanf("%d", &b);
    
       return a+b;
    }
    
    main()
    {
       int sum;
        ...
        sum = calculate();
        ...
        return 0;
    }
    or you can define it at the end of main (conventional way) in which case you need to have a PROTOTYPE before main eg,

    Code:
    int calculate();   /* <-- prototype */
    
    main()
    {
       int sum;
        ...
        sum = calculate();
        ...
        return 0;
    }
    
    int calculate()
    {
       int a, b;
       /* prompt a*/
       scanf("%d", &a);
       /* prompt b */
       scanf("%d", &b);
    
       return a+b;
    }
    Hope this helps.

  6. #6
    ATH0 quzah's Avatar
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    For the record, you can prototype functions inside of other functions:
    Code:
    int main( void )
    {
        int myfunc( char * );
        int x;
    
        x = myfunc( "Hello" );
    
        return !!x; /* Just for fun. */
    }
    
    int myfunc( char * s )
    {
        printf( "%s\n", s );
        return 5;
    }
    Quzah.
    Hope is the first step on the road to disappointment.

  7. #7
    Banned master5001's Avatar
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    Building upon what Quzah just said:

    Code:
    #include <ctype.h>
    
    int main( void )
    {
        int myfunc( char *s) {
            for(;*s;s++)
                 *s = toupper(*s);
        }
        char s[] = "hello";
    
        myfunc(s);
        puts(s);
    
        return ~-1; /* Just for fun. */
    }

  8. #8
    Programming Sex-God Polymorphic OOP's Avatar
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    yeah, nested function definitions are not a part of the standard

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