Thread: Pointer problem

I have 2 structs as follows:

Code:

template <class T>
struct VList
{
	T wrd;
	VList<T> *nextVList, *nextRight;
	Vertex<T> *vTmpPtr;
};


template <class T>
struct Vertex
{
	T wrd;
	int pathLength;
	Vertex<T> *nextVertex;
};

I need to do the following :

vListHead->nextRight=tmp->vTmpPtr;

The error I receive is :

Cannot convert 'Vertex<String> *' to 'VList<String> *' in function Graph<String>::adjacencyList(Vertex<String> &)

Is there anyway I can do this??

sorry...forgot to put the function itself

Code:

void Graph<T>::adjacencyList (Vertex<T>& elem)
{
    VList<T> *tmp;
    
    tmp->vTmpPtr=new Vertex<T>;

    if (!matchRes)
    {
	tmp->vTmpPtr->wrd=elem.wrd;
	tmp->vTmpPtr->pathLength=elem.pathLength;
	tmp->vTmpPtr->nextVertex=NULL;
                vListHead->nextRight=tmp->vTmpPtr;   <-----------
	vertexPtr=tmp->vTmpPtr;
    }
    else
    {
	tmp->vTmpPtr->wrd=elem.wrd;
	tmp->vTmpPtr->pathLength=elem.pathLength;
	tmp->vTmpPtr->nextVertex=NULL;
	vertexPtr->nextVertex=tmp->vTmpPtr;
	vertexPtr=vertexPtr->nextVertex;
    }
}

Doing

VList<T> *tmp;

tmp->vTmpPtr=new Vertex<T>;

shouldn't work (and may crash if you get your code to compile), as tmp is an unallocated pointer. You could try something like -

tmp = new VList<T>;

proceed as before. Then do

vListHead->nextRight=tmp;

in place of

vListHead->nextRight=tmp->vTmpPtr;

By doing what you have suggested, I am creating a new node of the struct VList....but my problem is that I have a node from VList struct and a node from Vertex struct and I need the nextRight ptr from VList to point to the node from Vertex.

Code:

 ______            ______
[____|_] -----> [____|_]
VList Node        Vertex Node

But, in your definition of a VList, the next right pointer points to a VList, not a Vertex node. The Vertex node is pointed to by your added VList node.

can you show me how I can get the VList nextRight ptr to point to the vTmpPtr....sorry for this

Copied from your example -

Code:

VList<T> *tmp = new VList<T>;
    
    tmp->vTmpPtr=new Vertex<T>;

    if (!matchRes)
    {
	tmp->vTmpPtr->wrd=elem.wrd;
	tmp->vTmpPtr->pathLength=elem.pathLength;
	tmp->vTmpPtr->nextVertex=NULL;
                vListHead->nextRight=tmp;
                //Don't know what vertexPtr is
	vertexPtr=tmp->vTmpPtr;
    }
//etc

If you've got something else in mind then you're going to have to rethink your data structures.