passing (...) as parameter

This is a discussion on passing (...) as parameter within the C Programming forums, part of the General Programming Boards category; Code: LE** listConstructor(int n2,...){ int i=0; .... do something with the input } What I want to do, is that ...

  1. #1
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    passing (...) as parameter

    Code:
    LE** listConstructor(int n2,...){
    	int i=0;
    	.... do something with the input
    }
    What I want to do, is that for as many int parameters passed something is done with the integers passed. How do I do that, without determining the size of the parameters in advance, but using ... ?

  2. #2
    CSharpener vart's Avatar
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    look for va_arg sample
    The first 90% of a project takes 90% of the time,
    the last 10% takes the other 90% of the time.

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    Hello,

    I've looked into the function passed, absolutely interesting. However I realized I don't know how I could you use it in my intended purpose, i.e declaration and definition of a linked list of integers.

    The 'dirty' way is:

    Code:
    struct le{
    	int key;
    	struct le* next;
    	struct le* prev;
    } ; typedef struct le LE;
    
    in main: 
    LE* list = (LE*) malloc(sizeof(LE));
    	list->key = 2;
    	list->next = (LE*) malloc(sizeof(LE));
    	list->next->key = 14;
    	list->next->next = (LE*) malloc(sizeof(LE));
    	list->next->next->key = 56;
    	list->next->next->next = (LE*) malloc(sizeof(LE));
    	list->next->next->next->key = 98;
    	list->next->next->next->next = (LE*) malloc(sizeof(LE));
    	list->next->next->next->next->key = 4;
    	list->next->next->next->next->next = (LE*) malloc(sizeof(LE));
    	list->next->next->next->next->next->key = 34;
    	list->next->next->next->next->next->next = (LE*) malloc(sizeof(LE));
    	list->next->next->next->next->next->next->key = 18;
    	list->next->next->next->next->next->next->next = (LE*) malloc(sizeof(LE));
    	list->next->next->next->next->next->next->next->key = 1;
    	list->next->next->next->next->next->next->next->next = (LE*) malloc(sizeof(LE));
    	list->next->next->next->next->next->next->next->next->key = 0;
    	list->next->next->next->next->next->next->next->next->next = (LE*) malloc(sizeof(LE));
    	list->next->next->next->next->next->next->next->next->next->key = 88;
    But any loop/recursive solution? Besides above I didn't allocates and point the prev pointers, which would double the lines of code.
    Last edited by simpatico_qa; 03-26-2009 at 04:07 PM.

  4. #4
    CSharpener vart's Avatar
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    start by providing some API for working with your list

    like

    list_inseart(LE** pList, int newValue);
    list_print(LE* List);

    etc

    when you'll have such functions for working with the list - writing a function that adds arbitrary number of integers will be a lot easier
    The first 90% of a project takes 90% of the time,
    the last 10% takes the other 90% of the time.

  5. #5
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    But if so, initializing the listnode shall always be the long way I did? I've functions that work on the list but they don't declare and define nodes.

  6. #6
    CSharpener vart's Avatar
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    Quote Originally Posted by simpatico_qa View Post
    But if so, initializing the listnode shall always be the long way I did? I've functions that work on the list but they don't declare and define nodes.
    why?
    The first 90% of a project takes 90% of the time,
    the last 10% takes the other 90% of the time.

  7. #7
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    because I asked for code that given a size and/or values will declare and define a list node accordingly. Yet u replied with something else (creating elements one at the time, when needed).

  8. #8
    Captain Crash brewbuck's Avatar
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    Quote Originally Posted by simpatico_qa View Post
    because I asked for code that given a size and/or values will declare and define a list node accordingly. Yet u replied with something else (creating elements one at the time, when needed).
    vart is just suggesting good code architecture. It doesn't bear directly on variable arguments but it's still good advice.

    I would suggest a function skeleton like this:

    Code:
    #include <stdarg.h>
    
    LE* listConstructor(int n2, ...)
    {
        LE *list = NULL;
        va_list valist;
    
        va_start(valist, n2);
        while(n2 > 0)
        {
            list = listAppend(list, va_arg(valist, LE *));
            --n2;
        }
        va_end(valist);
        return list;
    }
    This assumes a listAppend() function which appends the given element to the list... In practice this function will be a bit more complicated, but it shows how to use the va_* functions
    Code:
    //try
    //{
    	if (a) do { f( b); } while(1);
    	else   do { f(!b); } while(1);
    //}

  9. #9
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    Okay..I've several problems:

    1. I'm trying to set the 'backward/previous' links for a doubly linked list.
    My method is the following:
    Code:
    void setPrevLinks(LE* lis){
    	if (lis != NULL) return;
    	else{
    		lis->next->prev = lis;
    		setPrevLinks(lis->next);
    		return;
    	}
    }
    and I test it with:

    Code:
    setPrevLinks(list);
    	printf("%d\t",list->next->prev->key);
    Yet I get a bus error.

    Any feedback?

    [/code]

  10. #10
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    Hallo, any help on this?

  11. #11
    Captain Crash brewbuck's Avatar
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    Quote Originally Posted by simpatico_qa View Post
    Code:
    void setPrevLinks(LE* lis){
    	if (lis != NULL) return;
    So, you return if the pointer is NOT null? And you continue if it is? Hmm...
    Code:
    //try
    //{
    	if (a) do { f( b); } while(1);
    	else   do { f(!b); } while(1);
    //}

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