Do I need to create a destructor for my stack class? or does the compiler use one

Well Im creating a stack class using c++ and I'm not sure if I should create a destructor for my class. Is a constructor really needed even though Im using delete in my of my functions? Well here is my code, thanks for looking?

Code:

#include "stack.h"  // Stack class specification file

Stack::Stack() { top = NULL; }  // default constructor

bool Stack::isEmpty() {
  return top == NULL;
}  // end isEmpty

void Stack::push(StackItemType itemIn) {
  StackItems *newItem = new StackItems();  // create new node
  newItem->item = itemIn; // load values
  newItem->below = top;
  top = newItem; // make top point to this new item
}  // end push

bool Stack::pop() {
  if (isEmpty()) return false;

  // temporarily save current top pointer location so it can
  //   be later deleted (dynamic memory freed)
  StackItems *tempTop = top;

  top = top->below; // move top to one below it
  delete tempTop; // free space allocated to old top
  return true;
}  // end pop

bool Stack::pop(StackItemType& stackTop) {
 if (isEmpty()) return false;

  // stack is not empty; retrieve top
  stackTop = top->item;
  pop();
  return true;
}  // end pop

bool Stack::getTop(StackItemType& stackTop) {
  if (isEmpty()) return false;

  // stack is not empty; retrieve top
  stackTop = top->item;
  return true;
}  // end getTop

void Stack::displayAll() {
  if (isEmpty()) cout << "Stack is empty." << endl;
  StackItems *temp = top;
  while (temp != NULL) {
    cout << temp->item << endl;
    temp = temp->below;
    }
} // end displayAll

int Stack::getLength() {
  StackItems *temp = top;
  int count = 0;
  while (temp != NULL) {
    count++;
    temp = temp->below;
    }
  return count;
} // end getLength

also what is a good way of retreaving the item from the bottom? I just can't think of any way. The bottom item in the stack will have a null pointer to the one below it, but I just can't seem to properly put it in code.

Code:

bool Stack::getbottom(StackItemType& stackb) {
  if (isEmpty()) return false;

  // stack is not empty; retrieve bottom
  top->below=NULL;
 
  return true;
}

Originally Posted by newbc

Well Im creating a stack class using c++ and I'm not sure if I should create a constructor for my class. Is a constructor really needed even though Im using delete in my of my functions? Well here is my code, thanks for looking?

Define need. Should I be able to use isEmpty on a newly constructed stack? If so, then yes, you do. In fact, should I use isEmpty at all? Stack::pop needs to NULL the pointers it deletes.

Originally Posted by newbc

also what is a good way of retreaving the item from the bottom? I just can't think of any way. The bottom item in the stack will have a null pointer to the one below it, but I just can't seem to properly put it in code.

Use a doubly linked list to represent the stack internally and maintain a pointer to the tail.

whiteflags

Do you mean to have a back and front pointer like queues? if so my teacher doesn't like that he wants us to do it like this, by just having a top pointer.

Originally Posted by newbc

also what is a good way of retreaving the item from the bottom?

When the stack has exactly one item, just access the top item.

Originally Posted by laserlight

When the stack has exactly one item, just access the top item.

LOL, that be great.

well here is my second code. I modify my second display function since it displays all the values until reaching null. what i want it to do is just print the number that is the bottom number before reaching null. So far I have done a horrible job.

Code:

bool Stack::getb() {

 if (isEmpty()) cout << "Stack is empty." << endl;
  StackItems *temp = top;

  while (temp != NULL) {

       if(top->below=NULL){
              cout << temp->item << endl;
             //temp = temp->below;
       }//end if

    temp = temp->below;
   }
} // end

Originally Posted by newbc

LOL, that be great.

I'm not joking.

Originally Posted by newbc

I modify my second display function since it displays all the values until reaching null. what i want it to do is just print the number that is the bottom number before reaching null.

Don't do this. If the user wants to print the bottom number, he/she should pop all the ones above it first. This is the notion of a stack.

If you want to access the bottom item like this, don't create a stack. Create a linked list where you track the tail.

Oh, and for the code you posted, beware the difference between = and ==.

ok I think I figured out how to print item on the bottom;

Any help on how to create the descructor?
we just converted to c++ like two weeks ago.

Originally Posted by newbc

ok I think I figured out how to print item on the bottom;

What did you do?

To check: if it a requirement that your class provide a member function to access/print the bottom item on the stack, as a special case?

Originally Posted by newbc

Any help on how to create the descructor?

Loop over the items and destroy them.

What do you mean by "Loop over the items and destroy them."

Well one way would be to do

Code:

while (pop());