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Pointers in C++

 
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Pointers in C++, Its About pointers.
jignesh145
post 8 Apr, 2006 - 06:50 AM
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CODE

#include<iostream.h>
#include<conio.h>

struct link
 {
   int data;
   link* next;
 };

class linklist
 {
   private:
     link* first;

   public:
     linklist()
       {
         first = NULL;
       }
     void addItem(int d);
     void display();
  };

void linklist::addItem(int d)
 {
   link* newlink = new link;
   newlink->data = d;
 newlink->next = first;
   first = newlink;
 }
void linklist::display()
 {
   int temp = 0;
   link* current = first;
   while(current != NULL)
     {
       cout<< endl<<"The Data at node: " << temp << " " <<current->data<<endl;
       current = current->next;
       temp++;
     }
   }

void main()
 {
    linklist l1;   // why not - linklist l1 = new linklist();
    l1.addItem(12);
    l1.addItem(14);
    l1.addItem(15);
    l1.addItem(20);

    l1.display();
    getch();
 }


Question:-----Why i cant create object of linklist using new operator.........linklist l1 = new linklist();

This post has been edited by Dark_Nexus: 9 Apr, 2006 - 09:38 PM
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William_Wilson
post 8 Apr, 2006 - 08:33 AM
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Though i'm not sure this is the place to have asked this question, it is a simple answer.
when you use the 'new' command it allocates memory, this memory is stored on the heap, thus it is created dynamically. In C/C++ when you do this, you must create a pointer to a memory location, not just declare it (I assume you have done java or some language which allows this)
do this instead:
CODE

linklist* l1 = new linklist();


then to access parts of l1 you must use:
CODE

l1->additem(); //for example

read as l1 points to.
It is all about pointers, even in variable creation.
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Mrafcho001
post 8 Apr, 2006 - 08:34 AM
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because you are not creating a pointer you are creating an object

linkedlist* l1 = new linkedlist; // now you are creating a pointer.

Also this should go in the C++ forums, not introduction.

This post has been edited by Mrafcho001: 8 Apr, 2006 - 08:35 AM
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