how to add a parameter to the function

This is a discussion on how to add a parameter to the function within the C Programming forums, part of the General Programming Boards category; How do I add one more argument to an existing function which is called by other functions from various modules ...

  1. #1
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    how to add a parameter to the function

    How do I add one more argument to an existing function which is called by other functions from various modules of the project?
    I would like to add this new argument without or minimum risk. Is there a way to avoid compilation of the modules from which it is called?
    (There is a separate header file containing the definition of the function)


    Thanks in advance.

  2. #2
    CSharpener vart's Avatar
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    no you cannot do it, you should also pass the additional parameter...

    What you can do - to write a function with another name and additional parameter
    and replace the body of the old function with the call to the new one

    Then all calls to the old one can be leaved untoched, and new places will call the new function

    Code:
    int doWork(int a, int b) //old function
    {
      return doWorkNew(a,b,10 /*default value for the new paraameter*/);
    }
    
    int doWorkNew(int a, int b, int c)
    {
    //copy here the body of the old doWork function and modify it to process the new parameter
    }
    The first 90% of a project takes 90% of the time,
    the last 10% takes the other 90% of the time.

  3. #3
    Register User andor's Avatar
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    Asume that you define function like this:
    Code:
    int foo(void *);
    than you can pass to function different number of arguments. Okay its only one real argument but void * can point to array of arguments.
    Code:
    #include <stdio.h>
    
    int foo(void *);
    
    int main()
    {
       char arg1[] = {2, 1, 2};
       char arg2[] = {3, 1, 2, 3};
    
       printf("%d\n", foo((void *) arg1));
       printf("%d\n", foo((void *) arg2));
      
      return 0;
    }
    
    int foo(void * arg)
    {
       int acc=0, i;
       char * tmp = arg;
       
    /* first element of array is num of arguments */   
       for (i=0; i<tmp[0]; i++)
       {
          acc += tmp[i+1];
       }
       
       return acc;
    }

  4. #4
    CSharpener vart's Avatar
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    Quote Originally Posted by andor
    Asume that you define function like this:
    Code:
    int foo(void *);
    than you can pass to function different number of arguments. Okay its only one real argument but void * can point to array of arguments.
    Code:
    #include <stdio.h>
    
    int foo(void *);
    
    int main()
    {
       char arg1[] = {2, 1, 2};
       char arg2[] = {3, 1, 2, 3};
    
       printf("%d\n", foo((void *) arg1));
       printf("%d\n", foo((void *) arg2));
      
      return 0;
    }
    
    int foo(void * arg)
    {
       int acc=0, i;
       char * tmp = arg;
       
    /* first element of array is num of arguments */   
       for (i=0; i<tmp[0]; i++)
       {
          acc += tmp[i+1];
       }
       
       return acc;
    }
    int this case better to pass the char* pointer without cast
    The first 90% of a project takes 90% of the time,
    the last 10% takes the other 90% of the time.

  5. #5
    ATH0 quzah's Avatar
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    No you cannot pass a different number of arguments. You're stil passing one argument. You're passing an array. That's one argument. Void pointers don't help you get around that.


    Quzah.
    Hope is the first step on the road to disappointment.

  6. #6
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    Thanks a lot for your suggestions vart ,andor & quzah !

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