Returning pointer to a struct defined inside a class, multiple scope operators

my header file for a basic binary tree includes the following:

Code:

template<typename T>
class Btree{
    // OVERVIEW:    a binary tree with flexible structure that is not sorted

private:

    struct node {            //a container object 
        node *left;        //left and right tree
        node *right;
        T *o;        // pointer to  object of node
    };

public:

    node *root;    //pointer to the root of the tree (NULL if empty)

    node* insert (node *parent, T *child, int child);
    //MODIFIES:    this
    //EFFECTS:    creates a node that stores a pointer to the new child 
    //        and returns the pointer to the node of the new child    
    //        the integer child is either 0, for left child,
    //        or anything else for right child    

//    void printTree (node * root);
    //EFFECTS:    takes the root of a tree and prints the tree's 
    //        coordinates  
    
    Btree();    //ctor
    Btree(){}    //dtor


};

#include "btree.cpp"

-----------------------------------------------------------------------------------------

my .cpp looks like this, and not that it is included at the bottom of my header to avoid template compiler errors:

Code:

template <typename T>
Btree<T> :: node * Btree<T>::insert (node *parent, T *child, int child)

{
    node *np = new node;
    np-> o = child;    
    np->left = NULL;
    np->right  = NULL;
    if (child == 0)
        parent->left = np;
    else
        parent->right = np;
    return np;
}

however, i get the following compiler error:
btree.cpp:3: error: expected constructor, destructor, or type conversion before ‘*’ token

i'm compiling on 4.1.2 of the g++ compiler

Can anyone help!?!?! http://im.cprogramming.com/images/smilies/frown.png

> node* insert (node *parent, T *child, int child);
Why does two of them has the same name ?

>Btree<T> :: node * Btree<T>::insert (node *parent, T *child, int child)
Apparently, a newer version of the compiler will you better error messages.

Originally Posted by g++

a.cpp:34:1: error: need ‘typename’ before ‘Btree<T>::node’ because ‘Btree<T>’ is a dependent scope

The error literally instructs you what to do (I had this a while ago.. and totally ignored it thinking it meant something else!..don't do that.)

Also.. this can't be done:

Code:

    Btree();    //ctor
    Btree(){}    //dtor

THANK YOU! so helpful!

when I removed all the templates I am getting errors again. I followed what others recommend and my code looks like this:

Code:

class Btree{
    // OVERVIEW:    a binary tree that is not sorted

private:

    struct node {            //a container object 
        node *left;        //if the direction is straight
        node *right;        //if a right turn is made
        node *parent;        // points to the parent
        tile *t;        // pointer to  object of node
    };

public:

    node *root;    //pointer to the root of the tree (NULL if empty)

    node * insert (tile *parent, tile *child, int childNum);
    //MODIFIES:    this
    //EFFECTS:    creates a node that stores a pointer to the new child 
    //        and returns the pointer to the node of the new child    
    //        the integer child is either 0, for left child,
    //        or anything else for right child
    //        for the purposes of this project, all right turns
    //        are stored on the right subtree

    tile * removeAll(node *root);
    //EFFECTS:    deletes all nodes from the tree. called in dtor
    
    Btree();    //ctor
    Btree(tile *o);    //alternative ctor, sets root to o
    ~Btree();    //dtor


};

and the .cpp file has this now

Code:

Btree :: node * Btree ::insert(node *parent, tile *child, int childNum)
{
    node *np = new node;
    np-> t = child;    
    np->left = NULL;
    np->right  = NULL;
    if (root == NULL){
        root = np;
    } else{
        np->parent = parent;
        if (childNum == 0)
            parent->left = np;
        else
            parent->right = np;
    }
    return np;
}

with this compiler error:

btree.cpp:3: error: prototype for ‘Btree::node* Btree::insert(Btree::node*, tile*, int)’ does not match any in class ‘Btree’
btree.h:31: error: candidate is: Btree::node* Btree::insert(tile*, tile*, int)

any ideas?!

Read the error message. It says that your function prototype in line 3 of btree.cpp does not match the prototype in line 31 of the header.