Re: Non destructive summation of nodes (Linked List/FIFO Queue)

[Larry Hazel <lhhazel@otelco.net>]

Liddle Feesh wrote:
> 
> Hi,
> 
> Firstly - thankyou to everyone (Larry Hazel, Gautier, Ed Falis, Michal
> Nowak, Machael Bode & others) for your kinds assitance in helping me take my
> first steps in the great language of Ada95.
> 
> I am a little confused, however - at how to count the number of items in a
> linked list, without destroying the items in the process.
> 
> Basically, I want to do this:
> 
> If queue is empty
>         display warning message
> Else
>         loop while next pointer on node is not null
>                     print node's value
>         end loop
>         print last node's value
> end if
> 
> *So that I can loop through all the nodes. If this isn't possible, then
> another solution could be:*
> 
> Declare Count_Of_Elements as Integer
> Set Count_Of_Elements = 0
> While Not Queue.Head = null
>           Increment Count_Of_Elements = Count of Elements + 1 -- (Increment
> Count)
> End Loop
> Print Count_Of_Elements
> 
> ----
> However, writing the above in Ada without destroying the queue is tricky.
> Michal suggested:
> 
> while not (Queue.Is_Empty_Queue(Queue) ) loop
>         Queues.Remove (Element, Queue);
>         Put(Element);
>         New_Line;
> end loop;
> 
> ------
> 
> However, the above basically removes each node whilst 'counting' back the
> values stored in each.
> 
> And for those that have just joined this conversation, I am trying to create
> a display function/procedure that gives me a count of the elements in the
> queue.
> 
> TIA!
> 
> Mike
> 
Your package doesn't have a non-destructive get function or a way to iterate
over the queue getting each element  Looks like you need these.  Modify the
queue package to add them.

Larry