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Error: LNK2019

bardicer (31)
First off, my code in its entirety is here: http://codepad.org/fcOLWhWs

I have three classes: an ordered list class which is composed of a binary search tree for implementation, the binary search tree is composed of a class called TreeNode in turn.

I know the main program for testing the implementation isn't done - but I got this error while trying to test the insert method. At the bottom of the paste, it shows my errors I'm receiving.

If I declare an instance of OLType, and I use -> to refer to something (which I know I can't because the instance isn't a pointer so no dereferencing needed) I get an error.

If I use a . (say myList.insert() ), it yells at me and tells me there has to be a class/struct/union on the left of the . operator - which there is.

If I declare myList to be a pointer to an object of OLType, I get yelled at because there are unresolved external symbols. However, in a fit of blind frustration, and trying to make my compiler as irritated as I was, I took the pointer and attempted the . operator on it, and the compiler said "Did you intend to use ->?" So...compiler/linker 2 - me 0. Can anyone tell me where I'm going wrong here?
Last edited on
bardicer (31)
Here's the code in case y'all prefer seeing it here as opposed to a pastebin:


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//-----------------------TreeNode.h


#ifndef TREENODE__H
#define TREENODE__H

template <class T>
struct TreeNode {
  T item;
  TreeNode<T> *left;
  TreeNode<T> *right;
};

#endif

//-------------------BST.h

#ifndef BST__H
#define BST__H

#include "TreeNode.h"
#include <iostream>
  using namespace std;
enum TravType {PRE, POST, IN};



template <class T>
class BST {
  protected:
    TreeNode<T> *root;
    size_t count;
  public:
    BST();
    ~BST();
    const bool empty();
    void erase(const T&);
    const bool find(const T&);
    void insert(const T&);
    const size_t size();
    const void traverse(ostream&, TravType);
  private:
    T predecessor(TreeNode<T>*);
    void destroy(TreeNode<T>*&);
    const bool find_R(const T&, TreeNode<T>*);
    void erase_R(const T&, TreeNode<T>*&);
    void insert_R(const T&, TreeNode<T>*&);
    const void inorder(ostream&, TreeNode<T>*);
    const void postorder(ostream&, TreeNode<T>*);
    const void preorder(ostream&, TreeNode<T>*);

};

template <class T>
BST<T>::~BST() {
  destroy(root);
}
template <class T>
const bool BST<T>::empty() {
  return count == 0;
}
template <class T>
void BST<T>::erase(const T& item) {
  erase_R(item, root);
}
template <class T>
const bool BST<T>::find(const T& item) {
  return find_R(item, root);
}

template <class T>
void BST<T>::insert(const T& item) {
  insert_R(item, root);
}

template <class T>
const size_t BST<T>::size() {
  return count;
}

template <class T>
const void BST<T>::traverse(ostream& out, TravType trav) {
  if(trav == PRE)
    preorder(out, root);
  else if(trav == POST)
    postorder(out, root);
  else
    inorder(out, root);
}

template <class T>
void BST<T>::destroy(TreeNode<T> *&root) {
  root = NULL;
  count = 0;
}


template <class T>
const bool BST<T>::find_R(const T& item, TreeNode<T> *root) {
  if(item < root->item)
    find_R(item, root->left);
  else if(item > root->item)
    find_R(item, root->right);
  return item == root->item;
}

template <class T>
void BST<T>::erase_R(const T& item, TreeNode<T> *&root) {


  if(item < root->item) {
    predecessor = root;
    erase_R(item, root->left);
  }
  else if(item > root->item) {
    predecessor = root;
    erase_R(item, root->right);
  }

  else if(item == root->item) {
    //-----Case 1: No children
    if((root->left == NULL) && (root->right == NULL)) {
      if(predecessor->left == root)
        predecessor->left = NULL;
      else
        predecessor->right = NULL;
      delete root;
      count--;
    }

    else if((root->left != NULL) && (root->right == NULL)) {
      if(predecessor->left == root) 
        predecessor->left = root->left;
      else
        predecessor->right = root->left;
      delete root;
      count--;
    }

    else if((root->left == NULL) && (root->right != NULL)) {
      if(predecessor->left == root)
        predecessor->left = root->right;
      else
        predecessor->right = root->right;
      delete root;
      count--;
    }

    else if((root->left != NULL) && (root->right != NULL)) {
      TreeNode<T> *temp;  
      temp = root->left;
      while(temp->right != NULL) {
        predecessor = temp;
        temp = temp->right;
      }
      predecessor->right = temp->left;
      delete temp;
      count--;
    }
  }

}
template <class T>
const void BST<T>::inorder(ostream& out, TreeNode<T> *root) {
  if(root->left != NULL)
    inorder(out, root->left);
  out << " " << root->item;
}
template <class T>
const void BST<T>::postorder(ostream& out, TreeNode<T> *root) {
  if(root->left != NULL)
    postorder(out, root->left);
  if(root->right != NULL)
    postorder(out, root->right);
  out << " " << root->item;
}
template <class T>
const void BST<T>::preorder(ostream& out, TreeNode<T> *root) {
  out << " " << root->item;
  if(root->left != NULL)
    preorder(out, root->left);
  if(root->right != NULL)
    preorder(out, root->right);
}
#endif

//---------------------OLType.h

#ifndef OLTYPE__H
#define OLTYPE__H

#include "BST.h"


template <class T>
class OLType {
  friend ostream& operator << (ostream& out, const OLType<T>& myList) {
    if(trav == PRE)
      myList.traverse(out, PRE);
    else if(trav == POST)
      myList.traverse(out, POST);
    else
      myList.traverse(out, IN);
  }
  public:
    OLType();
    const bool empty();
    const bool find(const T&);
    void erase(const T&);
    void insert(const T&);
    const size_t size();
  protected: 
    BST<T> list;
};
template <class T>
const bool OLType<T>::empty() {
  return list.empty();
}

template <class T>
const bool OLType<T>::find(const T& item) {
  return list.find(item);
}

template <class T>
void OLType<T>::erase(const T& item) {
  list.erase(item);
}

template <class T>
void OLType<T>::insert(const T& item) {
  list.insert(item);
}

template <class T>
const size_t OLType<T>::size() {
  return list.size();
}

#endif


//------------------BSTmain.cpp

#include "OLType.h"
#include <iostream>
  using namespace std;

int main() {
  
     /* ERROR CASE 1:  
   OLType<int> myList;  
     ERROR CAUSED BY PRECEDING LINE: 
     1>  LINK : C:\Users\Nick\Documents\Visual Studio 2010\Projects\Binary\Debug\Binary.exe not found or not built by the last incremental link; performing full link

     1>BSTmain.obj : error LNK2019: unresolved external symbol "public: __thiscall OLType<int>::OLType<int>(void)" (??0?$OLType@H@@QAE@XZ) referenced in function _main

     1>C:\Users\Nick\Documents\Visual Studio 2010\Projects\Binary\Debug\Binary.exe : fatal error LNK1120: 1 unresolved externals */

     /* ERROR CASE 2:
   OLType<int> *myList; // No error by this statement alone...however...
   myList = new OLType<int>();
     ERROR CAUSED BY PRECEDING LINE:
     1>BSTmain.obj : error LNK2019: unresolved external symbol "public: __thiscall OLType<int>::OLType<int>(void)" (??0?$OLType@H@@QAE@XZ) referenced in function _main
     1>C:\Users\Nick\Documents\Visual Studio 2010\Projects\Binary\Debug\Binary.exe : fatal error LNK1120: 1 unresolved externals
     */
  int choice = 0;
  int num = 0;
}
firedraco (6243)
You don't seem to ever define your constructor for your OLType class. Also, the constructor should probably be a template.
bardicer (31)
Okay I figured out the problem. In the class declarations, I included prototypes or declarations or whatever you wanna call 'em for the default constructors. However, because they're "default", I didn't think I'd have to put in a declaration. So...if you're reading this trying to find a solution to the same problem:

In your class method definitions, you might need to define the default constructors:

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class::class() {

}


Orrrr if it's a template (just in case):

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template <class T>
class<T>::class() {

}
bardicer (31)
That's exactly what it was firedraco. I didn't have any sort of constructor defined. Sorry for the delay in responding - I was fixing it when you posted, then I went and kicked myself hehe.
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