Thread: Circular queue base on struct.

Hi. Iam stuck with how to make a circular queue that are based on a struct. Have been reading about the implementation but cant really understand it fully.

Here is what i got so far.

Code:

#define SIZE 10
typedef struct
{
    char reg;
    char brand;
    int modelyear;
    int mileage;
}car;

typedef struct
{
    struct *car_queue;
    int start;
    int stop;
}circular;

car keyinput();


int main(int argc, char **argv)
{
    int i;
    car item[SIZE];
    
    printf("Add %d cars to the que.\n\n",SIZE);
    for(i=0;i<SIZE;i++){
        item[i]=keyinput();
    }
    return 0;
}


car keyinput()
{
    car item1;


    puts("Number:");
    scanf("%s",item1.reg);
    fflush(stdin);
    puts("");
    puts("Brand:");
    scanf("%s",item1.brand);
    fflush(stdin);
    puts("");
    puts("Modelyear:");
    scanf("%d",&(item1.modelyear));
    fflush(stdin);
    puts("");
    puts("Milage:");
    scanf("%d",&(item1.milage));
    fflush(stdin);


    return item1;
}

Whould be nice with some help here.

First step is turn up your compiler warnings.

Is the circular struct supposed to have a pointer to the array? Currently, the pointer in the circular struct has bad syntax. The circular structure should have a member called "size" so the code knows when to "wrap around" from the end of the array to the beginning of the array.

Originally Posted by camel-man

First step is turn up your compiler warnings.

I have been fixing some code that didnt seem so right.
First i have changed "struct *car_queue" to "car *car_queue[QUE_SIZE]" and after that i added this to the main, "circular que".

So now i tried to add this for my forloop:
"que.car_queue[i]=input();" then i got an error so then i thougth that i can have a "->" instead of "."

Now when i did this i get this error:

"invalid type argument of '->' (have 'circular')"

So what does it mean. I get that i does not want me to use "->"
do it want me to have 'circular' but what does it really mean.

I posted an answer to that just now. Changed the struct to this:

Code:

typedef struct
{
    char reg[25];
    char brand[25];
    int modelyear;
    int mileage;
}car;


typedef struct
{
    car *car_queue[QUE_SIZE];
    int start;
    int stop;
    
}circular;

added "circular que" to main.

car *car_queue[QUE_SIZE] is an array of pointers to struct car. I think what you want is a single pointer to struct car, which would be a pointer to the first element of the array (which would be a pointer to the array).

Originally Posted by rcgldr

car *car_queue[QUE_SIZE] is an array of pointers to struct car. I think what you want is a single pointer to struct car, which would be a pointer to the first element of the array (which would be a pointer to the array).

So what you are saying that is I should have a pointer like this "car *car_queue".

Originally Posted by Mogren3000

So what you are saying that is I should have a pointer like this "car *car_queue".

Yes, that would be a pointer to the first member of an array of struct cars.