BinaryTreeInterface.h

//  Created by Frank M. Carrano and Tim Henry.
//  Copyright (c) 2013 __Pearson Education__. All rights reserved.

/** Listing 15-1.
 @file BinaryTreeInterface.h */

#ifndef _BINARY_TREE_INTERFACE
#define _BINARY_TREE_INTERFACE

template<class ItemType>
class BinaryTreeInterface
{
public:
   /** Virtual destructor allows concrete implementations to clean up
       heap memory when the BinaryTree is discarded. */

   virtual ~BinaryTreeInterface() {}

   /** Gets the data that is in the root of this binary tree.
    @pre  The binary tree is not empty.
    @post  The root’s data has been returned, and the binary tree is unchanged.
    @return  The data in the root of the binary tree. */
   virtual ItemType getRootData() const = 0;

   /** Traverses this binary tree in preorder (inorder, postorder) and
       calls the function visit once for each node.
    @param visit A client-defined function that performs an operation on
       or with the data in each visited node. */

   //precondition: the tree has not been traversed
   //postcondition: the tree has been traversed
   //returnType: void
   virtual void preorderTraverse(void visit(ItemType&)) const = 0;

   //precondition: the tree has not been traversed
   //postcondition: the tree has been traversed
   //returnType: void
   virtual void inorderTraverse(void visit(ItemType&)) const = 0;

   //precondition: the tree has not been traversed
   //postcondition: the tree has been traversed
   //returnType: void
   virtual void postorderTraverse(void visit(ItemType&)) const = 0;
}; // end BinaryTreeInterface
#endif