Pass an entire struct

This is a discussion on Pass an entire struct within the C Programming forums, part of the General Programming Boards category; Hey guys ive search around on previous, and found some similar post but not exactly. Im trying to pass an ...

  1. #1
    Registered User cdonlan's Avatar
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    Pass an entire struct

    Hey guys ive search around on previous, and found some similar post but not exactly. Im trying to pass an entire array of structs to a function. The structure is declared as a local varriable in main ( my professor has a problem with global varriables) and it needs to be pass to a function.

    I was thinking something like this....

    Code:
    
    void option1(struct *data);
    
    int main()
    {
         struct my_struct{
              int x;
              char y;
          } data;
    
     option1( data);
      .
      .
      .
         return o;
    }
    void option1(struct *data)
    {
     // function stuff
    }
    or do i have to pass each element of the struct by itself.

    Code:
    void option1( int data.x, char data.y);

    thanks
    chris

  2. #2
    ~viaxd() viaxd's Avatar
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    to pass an array of structs you pass it just like any other array, that is you pass a pointer to the first element:
    Code:
    void do_smt(struct data *);
    ...
    struct data arr[LEN];
    do_smt(arr);
    :wq

  3. #3
    Registered User linuxdude's Avatar
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    Code:
    #include <stdio.h>
    
    struct bob{
            int x;
    };
    
    void pass(struct bob arg[50]);
    
    int main(void){
            struct bob new[50];
            int x;
            pass(new);
            for(x=0;x<50;x++){
                    printf("%d\n",new[x].x);
            }
            return 0;
    }
    
    void pass(struct bob arg[50]){
            int x;
            for(x=0;x<50;x++){
                    arg[x].x=1;
            }
    }
    Of course I use 'x' too much

  4. #4
    Registered User cdonlan's Avatar
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    OK makes since dont you have to use the arrow opperator to acces a particular elemet of the struct inside the function??

    such as...
    Code:
    arg[i]->x
    also could you use a type def to pass through the function.

    such as

    Code:
    void function1( //i dont know the parameter// data)
    
    
    
    typedef struct my_struct data;
    maybe??
    Last edited by cdonlan; 11-27-2004 at 12:53 PM.

  5. #5
    ~viaxd() viaxd's Avatar
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    no, since arg is an array of structs, not an array of pointers to structs.
    :wq

  6. #6
    Registered User linuxdude's Avatar
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    only if it is a pointer to a struct.

  7. #7
    Registered User cdonlan's Avatar
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    Man you guys are fast.

    Thanks a bunch

    chris

  8. #8
    Registered User cdonlan's Avatar
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    im still getting some warrnings

    Code:
    void option2(char *cat, struct data  *cars[50]);
    
    int main()
    {
    struct data{
    		char rank[2];
    		char name[80];
    		char state[12];
    		char year[5];
    		char category[2];
    		char cost[10];
    	};
    
    	struct data cars[50];
    
         option2(cars);
    
         return;
    }
    
    void option2(char *cat, struct data  *cars[50])
    {
    //function stuff
    }
    thanks

  9. #9
    & the hat of GPL slaying Thantos's Avatar
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    Well you prototyped the function to take a pointer to a char and an array of pointers to structs but pass it only a pointer to a struct.

  10. #10
    Registered User cdonlan's Avatar
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    ok i fixed that, but its still not working.

  11. #11
    & the hat of GPL slaying Thantos's Avatar
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    Post the new code and the exact warnings/errors

  12. #12
    Registered User cdonlan's Avatar
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    check PMed it to ya thantos.

  13. #13
    & the hat of GPL slaying Thantos's Avatar
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    I checked the code and sent it back to you. Please note that its a bad idea to PM another member your code without asking first. I asked you to post it so that I or another member could comment on it and everyone would have the chance to learn.

    Since you said you didn't want your code posted I won't but allow me to comment on it.

    Arrays are not pointers but they can degenerate into pointers. So when you pass an array to a function that wants a pointer there is no need for the &. Example

    Code:
    char arr[100];
    /* Improper scanf() */
    scanf("%s", &arr);
    /* Proper scanf() */
    scanf("%s", arr);
    Another note:
    Code:
    char *blah[10];
    Declares a variable called blah that is an array of 10 pointers to characters

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