I don't like doing this but i'm desperate

This is a discussion on I don't like doing this but i'm desperate within the C Programming forums, part of the General Programming Boards category; As the subject says: "I don't like doing this but i'm desperate"...I have analyzed my program bit by bit to ...

  1. #1
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    I don't like doing this but i'm desperate

    As the subject says: "I don't like doing this but i'm desperate"...I have analyzed my program bit by bit to try to figure out what I am doing wrong, but I haven't been able to find my mistake. It is a simple stack program, with no purpose. The problem is that I can execute the program without any problems, until I try to see the elements of my stack, then it says that there are no elements...which leads me to think that something is wrong in my push function.

    Here is the code that I have:
    PHP Code:
    /* Stack example */
    #include <stdio.h>

    struct information {
        
    int number;
        
    struct information *next;
    };

    struct information *first_element;                /* points to the first element */

    /* function prototypes */
    void push(void);            /* insert a new item into the stack */
    void pop(void);                /* remove an existing item from the stack */
    void show_stack(void);
    int show_menu(void);

    int main()
    {
        
    int choice;

        
    /* since the list is empty, the first element points to null */
        
    first_element = (struct information *) NULL;

        while((
    choice show_menu()) != 4)
        {
            switch(
    choice) {
                case 
    1push(); break;
                case 
    2pop(); break;
                case 
    3show_stack(); break;
                default: 
    printf("Not an element\n"); break;
            }
        }
    }
    void push()
    {
        
    /* create a pointer to the struct for the new element */
        
    struct information *new_element;

        
    /* obtain memory for the new element, make sure there is enough memory */
        
    new_element = (struct information *) malloc(sizeof(struct information));
        if (
    new_element == NULL) {
            
    printf("\nNot enough memory.");
        }
        else {
            
    /* obtain new data */
            
    printf("\nWhat number would you like to insert? ");
            
    scanf("%d", &new_element->number);

            if(
    first_element == NULL) {
                
    /* this is the first element being stored */
                
    first_element == new_element;
                
    new_element->next NULL;
                }
            else {
                
    /* new_element->next will now point to the element that the first element
                used to point to.  It ocuppies the first position */
                
    new_element->next first_element;
                
    first_element new_element;
            }
        }
    }

    void show_stack()
    {
        
    struct information *temp;
        
    int i;                    /* counter */
        
    0;

        
    /* start from the beginning */
        
    temp first_element;

        while(
    temp != NULL) {
            
    printf("%d -> "temp->number);
            
    i++;

            
    /* follow the -link- */
            
    temp temp->next;
        }

        if(
    == 0)
            
    printf("\nThere are no elements in the stack.");
        else
            
    printf("\nThere are %d element in the stack"i);
    }

    int show_menu()
    {
        
    int choice;

        
    printf("\n--- Options ---\n"
               "1. Push\n"
               "2. Pop\n"
               "3. Show stack\n"
               "4. Exit\n?"
    );
        
    scanf("%d", &choice);

        return 
    choice;

    I have taken out the "pop" function because it is working OK.
    I can't find the problem with the "push" function. Please help, I am going mad.

    Thanks.

  2. #2
    End Of Line Hammer's Avatar
    Join Date
    Apr 2002
    Posts
    6,231
    In function push()
    Code:
    if(first_element == NULL) {
       /* this is the first element being stored */
       first_element == new_element;
       new_element->next = NULL;
    }
    You are using double equals in error. It should be single for assignment.

    >first_element = new_element;
    When all else fails, read the instructions.
    If you're posting code, use code tags: [code] /* insert code here */ [/code]

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