CODEWITHSUNDEEP
c++copy-constructor
Rafael
Rafael

Reputation: 93

C++ Copy Constructor Linked Stack

so I have a copy constructor of a class over here...

template<class ItemType>
LinkedStack<ItemType>::LinkedStack(const LinkedStack<ItemType>& aStack)
{
// Point to nodes in original chain
Node<ItemType>* origChainPtr = aStack.topPtr;

if (origChainPtr == nullptr)
    topPtr = nullptr;  // Original stack is empty
else
{
    // Copy first node
    topPtr = new Node<ItemType>();
    topPtr->setItem(origChainPtr->getItem());

    // Point to last node in new chain
    Node<ItemType>* newChainPtr = topPtr;

    // Advance original-chain pointer
    origChainPtr = origChainPtr->getNext();

    // Copy remaining nodes
    while (origChainPtr != nullptr)
    {
        // Get next item from original chain
        ItemType nextItem = origChainPtr->getItem();

        // Create a new node containing the next item
        Node<ItemType>* newNodePtr = new Node<ItemType>(nextItem);

        // Link new node to end of new chain
        newChainPtr->setNext(newNodePtr);

        // Advance pointer to new last node
        newChainPtr = newChainPtr->getNext();

        // Advance original-chain pointer
        origChainPtr = origChainPtr->getNext();
    }  // end while

    newChainPtr->setNext(nullptr);           // Flag end of chain
}  // end if
}  // end copy constructor

And I did a simple program but my professor told me that I didn't use the copy constructor and I don't seem to find how to do it. All I got is this but it doesn't display the second object "lStack2".

Here is my main...

#include <iostream>
#include "LinkedStack.h"
using namespace std;

int main(){

int val1, val2, val3, val4;
LinkedStack<int> lStack1;

LinkedStack<int> lStack2;

lStack2 = lStack1;

cout << "Enter the first value: ";
cin >> val1;

cout << "Enter the second value: ";
cin >> val2;

cout << "Enter the third value: ";
cin >> val3;

cout << "Enter the fourth value: ";
cin >> val4;

lStack1.show();
lStack2.show();

return 0;
}

And here is my display function...

template <class ItemType>
void LinkedStack<ItemType>::show() const{

Node<ItemType>* entryPtr = topPtr;
while (entryPtr != nullptr){
    cout << entryPtr->getItem() << endl;
    entryPtr = entryPtr->getNext();
}
}

Can someone help to figure out how to implement the copy constructor?

Upvotes: 0

Views: 1358

Answers (2)

Bas in het Veld
Bas in het Veld

Reputation: 1312

lStack2 = lStack1

will call the assignment operator. To use the copy constructor you actually need to construct the object (when declaring it):

LinkedStack<int> lStack2(lStack1);

or

LinkedStack<int> lStack2 = lStack1;

Upvotes: 2

Olaf Dietsche
Olaf Dietsche

Reputation: 74028

You have two stacks

LinkedStack<int> lStack1;
LinkedStack<int> lStack2;

and then assign the first to the second

lStack2 = lStack1;

This utilizes the assignment operator.

To use the copy constructor, you would rather say

LinkedStack<int> lStack2(lStack1);

Upvotes: 3

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