Class Pointers

Hi im having a little problem understanding how class pointers work. Ill explain as best i can what i dont understand...

My problem:

Im trying to do a simple graph like data structure, and am having a few problems understanding how to reference the pointers and use them, also if im using them correctly.

The class A should be able to point to 6 neighbours of class A, each of these neighbours in turn have 6 neighbours and so on.

I have a class A like so

Code:

---


class A
{
    public:
        A();
      ~A();

      A *one, *two, *three, *four, *five, *six;
};

---

In A how do i reference the one two etc? Im trying something like below but am having problems.

Code:

---


#include <iostream>
#include "A.h"

using namespace std;

int main(int argc, char *argv[])
{

      A a,b;

      // a's first neighbour points to b's four neighbour
      a.one =  b;
      b.four =  a;
 
      return 0;
}

---

How do i get the pointer from a.one to point to object b? Am i using the correct notation? Sorry im new to pointers...!

Also have i defined the class A correctly for the problem im doing?

Sorry if this is a little vague!!!

Thanks

a and b are not pointers, they are objects. To assign their addresses to pointers you need to use the address-of operator:

Code:

---

a.one = &b;
b.four = &a;

---

>Also have i defined the class A correctly for the problem im doing?
You'll have fun with six links per object, but I don't see a problem with the declaration you have.

ah i see, thanks.

so object 'a' s one pointer refers object 'b' s four pointer?

Code:

---

                a.one = &b;
        b.four = &a;

---

>so object 'a' s one pointer refers object 'b' s four pointer?
Object a's one pointer refers to object b and object b's four pointer refers to a:

Code:

---

  ~  ~
~  b  ~
  ~  a
~  ~  ~
  ~  ~

---

This is what you want if you want two adjacent vertices in a graph structure representing six sided cells where the cells are defined as

Code:

---

  2
1  3
  @
6  4
  5

---

At least, that's what I'm assuming your graph looks like from the information you've given. :)

yes thats exactly the sort of lattice style structure !

so am i going about this the correct way?

i was thinking of a 2D array of cells to store these in, to help with working out the correct neighbour of each

>i was thinking of a 2D array of cells to store these in
I was thinking more of an undirected linked graph than an array. It's less awkward. :)

>I was thinking more of an undirected linked graph than an array. It's less awkward.
What the heck is an 'undirected linked graph'?

hm, is that much more difficult to do? im new with C++ (as u may have guessed !)

could you explain it a little more?

>What the heck is an 'undirected linked graph'?
More or less: http://www.nist.gov/dads/HTML/undirectgraf.html

I specified 'linked' to avoid confusion with an array based implementation, I was thinking pointer based. ;)

>is that much more difficult to do?
Well, graphs are a pain no matter what implementation you go with. I just find the linked implementations to be more flexible and easier to work with than array based implementations.