Thread: Passing lists to functions

hi again guys.half of the code is working now,but still struggling with pointers.my next problem now is passing the *front and *rear
second time in a function.

i want to use the enqueue function in a other function (for example,showqueue, a function that dequeues-prints-enqueues).

Code:

void showqueue(int qsiz,struct node **fro,struct node **rea)
{
 int q,va;
 struct node *tmpee;
 for (q=0;q<qsiz;q++)
 {
  dequeue(&va,&fro,&rea,&qsiz);
  if (q==0)
   printf("[%d]<--front\n",va);
  else if (q==qsiz)
   printf("[%d]<--rear",va); 
  else
   printf("[%d]\n",va); 
   tmpee=newnode(va);
  enqueue(&fro,&rea,tmpee,&qsiz);
 }

}

Any ideas?should i give up with all this?totally wrong?

How does your dequeue() function look like and with each function call you are increasing the level of indirection.
You might be better off just using a single level of indirection ie struct node *fro instead of struct ***node fro

i did not posted it to keep the code size small, since this is clearly a pointer syntax question but ok here it is.it works without problems now :

Code:

int dequeue(int *it,struct node **frr,struct node **rre,int *qsz)
{
 struct node *tmpe;  
 int dfl=0;
 if (*frr!=*rre)
 {
  *it=(*frr)->info;
  tmpe=*frr;             
  *frr=(*frr)->next;  
  free(tmpe);
  *qsz--;
  dfl=1;
 }
 else if ((*frr!=NULL) && (*frr==*rre))
 {
  *it=(*frr)->info;
  tmpe=*frr;            
  *frr=NULL;
  *rre=NULL;
  free(tmpe);
  *qsz=0;
  dfl=1; 
 }
 return dfl;
}

i am allowed only to use enqueue-dequeue to show the items of the queue.so is it possible to increase that level of indirection one more level further?

Why do you want add another level of indirection if all's well with the program??

nope there is a problem when i call enqueue and dequeue function in the showqueue.the **fro must pass to the two functions somehow and i cannot think of anything.

maybe you will understand my question from this:

1st level: main(): *front (pointer for structure)
2nd level showqueue: **fro (pointer of pointer of structure in order to be used in the function showqueue)
3rd level enqueue (called in showqueue): ??? (pointer of pointer of pointer of structure in order to be passed from showqueue to enqueue)

tried *&fro,&fro,&*fro in showqueue to pass the double pointer to enqueue but nothing worked.
did you understand where is the problem?

Originally Posted by Griever

nope there is a problem when i call enqueue and dequeue function in the showqueue.the **fro must pass to the two functions somehow and i cannot think of anything.

maybe you will understand my question from this:

1st level: main(): *front (pointer for structure)

From main() call enqueue() using struct node *fro.

Originally Posted by Griever

2nd level showqueue: **fro (pointer of pointer of structure in order to be used in the function showqueue)

You can again pass struct node *fro to showqueue; no need to pass struct node **fro

Originally Posted by Griever

3rd level enqueue (called in showqueue): ??? (pointer of pointer of pointer of structure in order to be passed from showqueue to enqueue)

Again pass struct node *fro to enqueue instead of struct node ***fro.

Originally Posted by Griever

tried *&fro,&fro,&*fro in showqueue to pass the double pointer to enqueue but nothing worked.

How about simply struct node *fro.

Originally Posted by Griever

did you understand where is the problem?

Trying...others may have better insights / ideas.

ah yes you are absolutely right... i wanted to convert my code in using pointers functioning like when i was using global variables that i did not make a simple check of what is actually needed to be pointed...i corrected almost everything.also i found that *qsz++ or *qsz-- did not work and i corrected it putting the ++ change in a variable (qq++; *qsz =qq and updating the pointer at the end of the process.thanks again for your quick responses and your time.

i upload the final version of my code to anyone who is interested(i changed every message and comment to english).could not have done it without your help.

code contains DOS commands ( system("PAUSE"); ,system("CLS"); )so it will not compile on non-windows environments.delete system("CLS"); and replace system("PAUSE"); with getchar(); to fix this.

thanks a lot.