Object defined recursively?

Hi everyone,

I'm working on an object (a Barnes-Hut tree) that contains a body, an octant, and 8 additional BHTrees inside of it. I originally wrote the code in java, where this worked quite simply. But now, I'm getting an error for each of the fields: error: field 'bTNW' has incomplete type

Here's the code:

#ifndef BHTREE_H
#define BHTREE_H

#include <iostream>
#include <math.h>
#include "Body.h"
#include "Oct.h"

using namespace std;

class BHTree {
Body body;
Oct oct;
BHTree bTNW;
BHTree bTNE;
BHTree bTSW;
BHTree bTSE;
BHTree bBNW;
BHTree bBNE;
BHTree bBSW;
BHTree bBSE;

public:
void set_values (Oct q);
// bool isExternal(BHTree t);
// void insert(Body b);
// void updateForce(Body b, double t);

};

void BHTree::set_values(Oct q){
oct=q;
}


#endif


I imagine it has something to do with C++'s forward declarations that don't really apply in java to functions and classes, but I'm not sure. Any help would be appreciated!

It is not possible to define the BHTree class with BHTree members. What you can do is to define BHTree* members.

Quote:

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Originally Posted by timboyk12

I originally wrote the code in java, where this worked quite simply.

---

It's because in Java you worked with pointers without much thinking about it (because every object is represented by a pointer (reference) to the object). This variable declaration in Java

BHTree x;

corresponds to this,

BHTree* x;

in C++.

In both cases you need to allocate objects dynamically using new. In C++ you must also delete the objects when you're finished with them. In Java you didn't need to because it has automatic garbage collection.

Quote:

---

Originally Posted by timboyk12

I'm working on an object (a Barnes-Hut tree) that contains a body, an octant, and 8 additional BHTrees inside of it.

---

If the object contains a body, an octant and 8 objects, each of them containing a body, an octant and 8 objects, each of them containing a body, an octant and 8 objects, each of them ..... I don't think you have enough memory to create such an object. Actually I don't think anyone has.