Learning Stack Operations. Copy and checking for empty not working,

[SacredFootball]

Hey all. I'm trying to learn stack operations and so far, I believe I've gotten push() and pop() down.

I seem to be stuck on copy, however. I cannot get a check for empty to work correctly.

typedef struct _node
{
   payload       data;
   struct _node *prev;
} node;

int main() {
   node    *rootPtr = NULL;
   node    *copyPtr = NULL;
   payload userInput;    

   // get user input for adding items to the stack, yada yada yada...
   copyPtr = stackCopy(rootPtr,copyPtr);
}

node *stackCopy(node *originalPtr, node *copyPtr)
{
   node    *tempPtr;             
   node    *tempTop;             
   payload  data;                
   node    *copyStackRev = NULL; 
   node    *copyStackOrg = NULL; 

   if (copyPtr != NULL) {
	   while (!copyPtr.empty()) {
		   copyPtr.pop();
	   }
   }
...
}

I'm getting a compile error stating that "left of '.empty' must have class/struct/union" so I know I'm using the .empty check incorrectly but I don't know what's wrong. I've check around the forum as well as on cplusplus.com and cannot find the issue.

[PMorphy]

Are you instantiating copyPtr anywhere?

[PMorphy]

Oh, I get it... You declared copyPtr in main, and you are using it int the StackCopy function. That function wouldn't know what copyPtr is.

[PMorphy]

Forget what I said about copyPtr, you're taking it in as an argument

[jonsca]

A "node" doesn't have an empty() method (if it did, you'd have to access it as copyPtr->empty() anyway, because copyPtr is a pointer). Did you mean to pass in stacks instead of nodes?

[SacredFootball]

A "node" doesn't have an empty() method (if it did, you'd have to access it as copyPtr->empty() anyway, because copyPtr is a pointer). Did you mean to pass in stacks instead of nodes?

I'm trying to delete and existing copy of copy stack. Checking for null and popping everything if it isn't null.

[jonsca]

Right, but you need a stack to do those operations on, not a node. A node has the two things that you have in the struct typedef. I'm not sure where you think the stack is coming from...