Ad:

C Discussion Thread
Marked Solved
Views: 1278

Mar 27th, 2009

how to implement queues in C?URGENT!!!!!

Expand Post »

i have made the following code...
but i am having problems in accessing it..

C Syntax (Toggle Plain Text)
 
//structure for queue
struct queue{
        int items[MAX];
        int front;
        int rear;
};
//decleration of the queues :que_term for the values printed on the terminal
struct queue que_mul2,que_mul3,que_mul5,que_sort,que_write,que_term;
 
 //initializing the queue
void InitQueue(queue &q)
{
        q.front=0;
        q.rear=0;
}
//checking if queue is empty
int isempty(queue &q)
{
        if(q.rear==q.front && q.front!=0)
                    return 1;
        else
                return 0;
}
//adding an element at the rear of the queue
void join(queue &q,int elem)
{
        q.items[q.rear]=elem;
        q.rear++;
}
//removing an element from the front of the queue
int leave(queue &q)
{
        int elem;
 
                elem=q.items[q.front];
                q.front++;
                return elem;
//        }
//        else
//                return -1;
}
//structure for queue
struct queue{
        int items[MAX];
        int front;
        int rear;
};
//decleration of the queues :que_term for the values printed on the terminal
struct queue que_mul2,que_mul3,que_mul5,que_sort,que_write,que_term;

 //initializing the queue
void InitQueue(queue &q)
{
        q.front=0;
        q.rear=0;
}
//checking if queue is empty
int isempty(queue &q)
{
        if(q.rear==q.front && q.front!=0)
                    return 1;
        else
                return 0;
}
//adding an element at the rear of the queue
void join(queue &q,int elem)
{
        q.items[q.rear]=elem;
        q.rear++;
}
//removing an element from the front of the queue
int leave(queue &q)
{
        int elem;

                elem=q.items[q.front];
                q.front++;
                return elem;
//        }
//        else
//                return -1;
}

these are the functions used but when i am calling this function as

join(que_write,1);

then que_write is not getting updated...
i have declared que_write as

struct queue que_write;
as mentioned above

pls tell me where im going wrong?
n is the struct type passed by reference by default like arrays?

vartikachandra

Reputation Points: 10

Solved Threads: 0

Newbie Poster

Offline

18 posts
since Jan 2009

Permalink

Mar 27th, 2009

Re: how to implement queues in C?URGENT!!!!!

Is this supposed to be C, not C++? I question this because of int isempty(queue &q) -- the parameter looks like a c++ reference.

Is that supposed to be circular queue where the front and back variables wrap around to 0 then the buffer items is filled up? If yes or no you need to add code to the join() function to wrap the front variable when it reached MAX, or not allow any more items in the queue when (front+1) > rear.

You need to firm up your understanding of the front and back variables.
front: This is where the next item will be inserted into the queue. When an item is inserted (see join function) this is the variable that should get incremented.

rear: This is where the next item will be removed from the queue. When an item is removed from the queue (see leave function) this is the variable that will be incremented.

You need checks in join() that front+1 does not exceed rear. And you need checks in leave() that rear+1 does not exceed front.

Last edited by Ancient Dragon; Mar 27th, 2009 at 5:04 pm.

Ancient Dragon

Sponsor

Team Colleague

Featured Poster

Reputation Points: 4835

Solved Threads: 1778

Still Learning

Offline

17,874 posts
since Aug 2005

Permalink

Mar 27th, 2009

Re: how to implement queues in C?URGENT!!!!!

i am invoking these methods as
in main

C Syntax (Toggle Plain Text)
 
int main(int argc,char *argv[])
{
        pthread_t threads[5];
        pthread_attr_t attr;
        int rc;
        void *status;
 
 
 
 
       //initializing the queues
        InitQueue(que_mul2);
        InitQueue(que_mul3);
        InitQueue(que_mul5);
        InitQueue(que_sort);
        InitQueue(que_write);
        InitQueue(que_term);
 
        //seed que_write with 1
        join(que_write,1);
 
}
int main(int argc,char *argv[])
{
        pthread_t threads[5];
        pthread_attr_t attr;
        int rc;
        void *status;




       //initializing the queues
        InitQueue(que_mul2);
        InitQueue(que_mul3);
        InitQueue(que_mul5);
        InitQueue(que_sort);
        InitQueue(que_write);
        InitQueue(que_term);

        //seed que_write with 1
        join(que_write,1);

}

its a fifo queue so thats why i used front as for deleting and rear for adding..
ya i will incorporate those condition checs..
but the main problem is that im not able to invoke these methods properly..
what shud i declare the queues as?

struct queue *q1;
or
struct queue q1;

coz i use
join(q1);

n this is C.In C++ it wud have been easier cuz u have objects.but here im not able to reflect the changes in the queue.

im getting error:

C Syntax (Toggle Plain Text)
 
Hamming.c:97: error: invalid initialization of reference of type 'queue&' from expression of type 'queue*'
Hamming.c:45: error: in passing argument 1 of 'int isempty(queue&)'
Hamming.c:100: error: invalid initialization of reference of type 'queue&' from expression of type 'queue*'
Hamming.c:59: error: in passing argument 1 of 'int leave(queue&)'
Hamming.c:102: error: invalid initialization of reference of type 'queue&' from expression of type 'queue*'
Hamming.c:53: error: in passing argument 1 of 'void join(queue&, int)'
Hamming.c:97: error: invalid initialization of reference of type 'queue&' from expression of type 'queue*'
Hamming.c:45: error: in passing argument 1 of 'int isempty(queue&)'
Hamming.c:100: error: invalid initialization of reference of type 'queue&' from expression of type 'queue*'
Hamming.c:59: error: in passing argument 1 of 'int leave(queue&)'
Hamming.c:102: error: invalid initialization of reference of type 'queue&' from expression of type 'queue*'
Hamming.c:53: error: in passing argument 1 of 'void join(queue&, int)'

pls help!!

vartikachandra

Reputation Points: 10

Solved Threads: 0

Newbie Poster

Offline

18 posts
since Jan 2009

Permalink

Mar 27th, 2009

Re: how to implement queues in C?URGENT!!!!!

In C languge you do not use the c++ reference & operator, but pointers

C Syntax (Toggle Plain Text)
void join(queue *q,int elem)
{
        q->items[q->rear]=elem;
        q->rear++;
}
void join(queue *q,int elem)
{
        q->items[q->rear]=elem;
        q->rear++;
}

And invoke it like this:
join( &que_write,1);

Last edited by Ancient Dragon; Mar 27th, 2009 at 5:36 pm.

Ancient Dragon

Sponsor

Team Colleague

Featured Poster

Reputation Points: 4835

Solved Threads: 1778

Still Learning

Offline

17,874 posts
since Aug 2005

Permalink

Mar 27th, 2009

Re: how to implement queues in C?URGENT!!!!!

Thanks!!this really helped!!

vartikachandra

Reputation Points: 10

Solved Threads: 0

Newbie Poster

Offline

18 posts
since Jan 2009

This thread is solved. Perhaps start a new thread instead?

This thread is more than three months old. Perhaps start a new thread instead?

Previous Thread in C Forum Timeline: SetTimer -- CallBack not called

Next Thread in C Forum Timeline: easy ? regarding area of a triangle

DaniWeb Message

Cancel Changes

User Name
Password