Getting the value of a variable rather than pointing to it. Need Help.

This is a discussion on Getting the value of a variable rather than pointing to it. Need Help. within the C Programming forums, part of the General Programming Boards category; Hey Hey, Code: int i; int number[100]; int placeHolder = 0; for(i = 0; i < 10; i++) { number[placeHolder] ...

  1. #1
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    Getting the value of a variable rather than pointing to it. Need Help.

    Hey Hey,

    Code:
    int i;
    int number[100];
    int placeHolder = 0;
    for(i = 0; i < 10; i++)
    {
        number[placeHolder] = i;
        placeHolder++;
    }
    I am writing a local function that is similar to the one above where i want to place the value of i into an array. So that in this example the array would hold the numbers from 0 through to 9.

    Is there any way that i can get the array to accept the value of i and store it without it changing? The program i have writes i in correctly for the 1st loop and then it all goes to hell the second time around.

    Thanks,
    -Nick

  2. #2
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    Hmm..... I'm missing it.

    Code:
    include <stdio.h>
    
    int main(void) {
    
        int i , j;
        int number[10];
        int placeHolder = 0;
    
        for(i = 0; i < 10; i++)
        {
            number[placeHolder] = i;
            placeHolder++;
    
        }
    
        for(j=0; j < 10; j++) {
            printf("El numero es: %d\n", number[j]);
        }
    
        return 0;
    }
    
    $gcc -Wall ar.c -o ar
    $./ar
    El numero es: 0
    El numero es: 1
    El numero es: 2
    El numero es: 3
    El numero es: 4
    El numero es: 5
    El numero es: 6
    El numero es: 7
    El numero es: 8
    El numero es: 9
    $

  3. #3
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    Hi even i did not find any problem with the code..as it run successfully and printed 0 to 9....if can print the output we can have a try

  4. #4
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    Quote Originally Posted by enggabhinandan
    Hi even i did not find any problem with the code..as it run successfully and printed 0 to 9....if can print the output we can have a try
    You're compiler is also ANSI compliant? Maybe your compiler and my compiler should get together and go bowling sometime.

  5. #5
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    yes u could be right..............which is the version of the compiler u use and on which platform

  6. #6
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    $uname -a
    Linux linux 2.6.5-7.155.29-default #1 Thu Jun 2 12:07:05 UTC 2005 i686 athlon i3 86 GNU/Linux
    $gcc --version
    gcc (GCC) 3.3.3 (SuSE Linux)
    Copyright (C) 2003 Free Software Foundation, Inc.
    This is free software; see the source for copying conditions. There is NO
    warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

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    Thanks for your reply.

    Ok, that was a poorly thought out example. Maybe that isn't the problem.

    I tried to make an example because it'd take ages to explain what the entire purpose of this code is. I have cut out the relevant parts of the code and placed them below. The array road_type holds 0's 1's and 2's in a random order, it's total size is num_roads.

    Code:
    #include <stdio.h>
    #include <stdlib.h>
    
    #define INTO 0
    #define OUTOF 1
    #define TWOWAY 2
    
    /* Prototypes of local functions */
    int get_route_list(int num_roads, int num_routes, int *road_type, int y, int x);
    
    int main(int argc, char *argv[])
    {
       
          /* Create an integer array showing possible routes i.e. road 1 to road 4 would be 14 */
       int j;
       int route_list[num_routes][1];
       for(j = 0; j < num_routes; j++)
       {
          route_list[j][0] = get_route_list(num_roads, num_routes, road_type, j, 0);
          route_list[j][1] = get_route_list(num_roads, num_routes, road_type, j, 1);
       }
       /* -----------------end route list thing-------------------*/
       return 0;
    }
    
         
    
    /* Create an array that lists the possible routes */
    int get_route_list(int num_roads, int num_routes, int *road_type, int y, int x)
    {
       int i, j;
       int route_list[num_routes][1];
       int place_holder = 0;
       for(i = 0; i <= num_roads; i++)
       {
          if(road_type[i] == TWOWAY || road_type[i] == INTO)
          {
             for(j = 0; j <= num_roads; j++)
             {
                if(road_type[j] == TWOWAY || road_type[j] == OUTOF)
                {
                   if(i == j)
                   {}
                    
                   else
                   {
                      route_list[place_holder][0] = i;
                      route_list[place_holder][1] = j;
                      /* #_#_#_#_#_#_#_#_# */
                      place_holder++;
                   }
                }
             }
          }
       }
       return route_list[y][x];
    }
    At that point where the #_#_ bit is the route list array is working fine for the first loop of that j for loop. Then when it loops through again i get problems, the program seems to assign the value of i to the route_list[place_holder][1] = j; I cant work out why this is.

    I'm struggling to explain this without posting the whole code and assignment details. If there is an obvious problem then it'd be great to hear what it is. Otherwise i'll just bang my head against the wall for another couple of hours and hope an answer falls out

    -Nick

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    I use the GNOME Terminal 2.7.3 in a Linux system and compile using the command line gcc play.c -Wall -o play

    thanks to everyone for their input so far

    -Nick

  9. #9
    and the hat of wrongness Salem's Avatar
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    > int route_list[num_routes][1];
    Wrong - you need int route_list[num_routes][2]; if you want to store [0] and [1] elements
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.
    I support http://www.ukip.org/ as the first necessary step to a free Europe.

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    Wicked Awesome

    Thanks, i had changed those for because it got rid of a segmentation fault a while back but forgot to right things again.

    Cheers Salem,
    -Nick

  11. #11
    and the hat of wrongness Salem's Avatar
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    > for(i = 0; i <= num_roads; i++)
    This is suspicious as well, since the normal loop for accessing an array is < n, not <= n
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.
    I support http://www.ukip.org/ as the first necessary step to a free Europe.

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