error C2663: : 2 overloads have no legal conversion for 'this' pointer

[melissak0421]

Ok I have a class with overloaded functions, and I keep getting this:Error 1 error C2663: 'BSearch<T>::inorder' : 2 overloads have no legal conversion for 'this' pointer

but I have checked the class and the functions and as far as I can tell they match like they are supposed to. here's the class

template <typename T>
class BSearch
{
public:
BSearch ();
~BSearch();
void destroy();
void insert(const T & item);
void inorder() const;
void preorder() const;
void postorder() const;
void deleteNode (const T & item);
T * search (const T & item) const;
int height() const;

private:
Node <T> * r;
T * search (Node<T> * & r, const T & item) const;
int height(Node<T> * & r ) const;
void destroy(Node<T> * & r, T & item);
void insert(Node<T> * & r, const T & item);
void deleteNode (Node <T> * & r, const T & item);
void inorder(Node <T> * & r) ;
void preorder(Node <T> * & r) ;
void postorder(Node <T> * & r) ;
};


and here's the functions:

template <typename T>
void BSearch<T>::inorder (Node <T> * & r)
{
if ( r!=0)
{
inorder (r->left);
cout << r->data;
inorder (r->right);
cout << r -> data;
}
}

template <typename T>
void BSearch<T>::inorder () const
{
inorder (r);
}

[Disch]

It's const correctness issues.

const member functions can not change member vars, and they can only call other const member functions. A const function cannot call a nonconst function on the same object.

Here, you have inorder() (a const function) calling inorder(Node<T>*&) (a non-const function). This is not allowed, hence the error.

The solution here is to make both inorder() functions const.

Also...

template <typename T>
void BSearch<T>::inorder () const
{
inorder (r);
}

Since this is const (because the function is const), that means the member 'r' will be const as well, which means you won't be able to pass it as a nonconst reference. A solution here would be to change inorder:

//template <typename T>
//void BSearch<T>::inorder (Node <T> * & r)   // bad

template <typename T>
void BSearch<T>::inorder (const Node <T> *r) const  // good 

Notice I make the function const, and I pass just a const pointer, not a non-const reference to a pointer (no need for the reference here).



Also... it's a really bad idea to name your member 'r'. It's not very descriptive at all. It's especially confusing since you use 'r' for all your parameter names.