Working with templates and error in C++

Question

I am trying to implement a red black tree with the use of templates. For example, when inserting an item to the tree, the key and the item should both be generic types. Till now, I implemented a header file which consists of a struct and functions to be implemented. However, I don't know if I'm using templates the right way. Also, when I tried to implement the 'Insert' function, the IDE gives the error: prototype for 'void RedBlackTree::InsertKey(Item*&, Key*&)' does not match any in class 'RedBlackTree' RedBlackTree.h

This is my header file:

#ifndef REDBLACKTREE_H_
#define REDBLACKTREE_H_

template <class Item, class Key>
class RedBlackTree
{
    typedef enum
    {
        BLACK,
        RED
    }ColourNode;

    typedef struct RBT
    {
        struct RBT *left;
        struct RBT *right;
        struct RBT *parent;
        struct RBT *root;
        ColourNode colour;
        Item item;
        Key key;
    }RBTNode;

    public:
        ~RedBlackTree(); // destructor
        RedBlackTree(Item, Key); // default constructor

        void InsertKey(Item, Key);
        int InsertFixUp(Item, Key);
        int RemoveKey(Item, Key);
        int FindKey(Item, Key);

    private:
        RedBlackTree<Item, Key> *rootPointer;
        RedBlackTree<Item, Key> *NILL_LEAF;

};

template <class Item, class Key>
void RedBlackTree<Item, Key>::InsertKey(Item *&T, Key *&z)
{
    //node* nil=tree->nil;
    //node* root=tree->root;
    RBTNode *y;
    RBTNode *x;
    y=T->nil;
    x=T->root;

    while(x != T->nil)
    {
        y=x;
        if((z->key)<(x->key))
            x=x->left;
        else
            x=x->right;
    }

    y=z->parent;

    if(y == T->nil)
        z=T->root;
    else
    if((z->key)<(y->key))
        z=y->left;
    else
        z=y->right;
        z->left=T->nil;
        z->right=T->nil;
        z->colour=RED;
        InsertFixUp(T,z);
}
#endif /* REDBLACKTREE_H_ */

Thanks in advance.

Answer 1

The problem is that the types of the arguments to InsertKey don't match the declaration. In the declaration the arguments are Item and Key , and in the implementation they are Item*& and Key*& (references to pointers). These need to match.

void InsertKey(Item, Key);
               ^^^^  ^^^
void RedBlackTree<Item, Key>::InsertKey(Item *&T, Key *&z)
                                        ^^^^^^^   ^^^^^^

Answer 2

You have to move the implementation of the function (the template) to the class definition.

template <class Item, class Key>
class RedBlackTree
{
//...
public:
    ~RedBlackTree(); // destructor
    RedBlackTree(Item, Key); // default constructor

    void InsertKey(Item *&T, Key *&z)
    {
        //...
    }

    //...
};