您好我每次在下面的代码中声明一个函数时都会收到错误消息error: expected initializer before '<' token。我对c ++中的模板不是很熟悉所以这个错误真的让我失望了。我已经尝试使用typename关键字，但它没有用。任何帮助都会很棒。
BinarySearchTree.h
#ifndef BINARY_SEARCH_TREE_H_
#define BINARY_SEARCH_TREE_H_
#include "dsexceptions.h"
#include <iostream.h> // For NULL
// Binary node and forward declaration because g++ does
// not understand nested classes.
template <class Comparable>
class BinarySearchTree;
template <class Comparable>
class BinaryNode
{
Comparable element;
BinaryNode *left;
BinaryNode *right;
BinaryNode( const Comparable & theElement, BinaryNode *lt, BinaryNode *rt )
: element( theElement ), left( lt ), right( rt ) { }
friend class BinarySearchTree<Comparable>;
};
// BinarySearchTree class
//
// CONSTRUCTION: with ITEM_NOT_FOUND object used to signal failed finds
//
// ******************PUBLIC OPERATIONS*********************
// void insert( x ) --> Insert x
// void remove( x ) --> Remove x
// Comparable find( x ) --> Return item that matches x
// Comparable findMin( ) --> Return smallest item
// Comparable findMax( ) --> Return largest item
// boolean isEmpty( ) --> Return true if empty; else false
// void makeEmpty( ) --> Remove all items
// void printTree( ) --> Print tree in sorted order
template <class Comparable>
class BinarySearchTree
{
public:
explicit BinarySearchTree( const Comparable & notFound );
BinarySearchTree( const BinarySearchTree & rhs );
~BinarySearchTree( );
const Comparable & findMin( ) const;
const Comparable & findMax( ) const;
const Comparable & find( const Comparable & x ) const;
bool isEmpty( ) const;
void printTree( ) const;
void makeEmpty( );
void insert( const Comparable & x );
void remove( const Comparable & x );
const BinarySearchTree & operator=( const BinarySearchTree & rhs );
private:
BinaryNode<Comparable> *root;
const Comparable ITEM_NOT_FOUND;
const Comparable & elementAt( BinaryNode<Comparable> *t ) const;
void insert( const Comparable & x, BinaryNode<Comparable> * & t ) const;
void remove( const Comparable & x, BinaryNode<Comparable> * & t ) const;
BinaryNode<Comparable> * findMin( BinaryNode<Comparable> *t ) const;
BinaryNode<Comparable> * findMax( BinaryNode<Comparable> *t ) const;
BinaryNode<Comparable> * find( const Comparable & x, BinaryNode<Comparable> *t ) const;
void makeEmpty( BinaryNode<Comparable> * & t ) const;
void printTree( BinaryNode<Comparable> *t ) const;
BinaryNode<Comparable> * clone( BinaryNode<Comparable> *t ) const;
};
#include "BinarySearchTree.cpp"
#endif
BinarySearchTree.cpp
#include "BinarySearchTree.h"
#include <iostream.h>
/**
* Implements an unbalanced binary search tree.
* Note that all "matching" is based on the < method.
*/
/**
* Construct the tree.
*/
template <class Comparable>
BinarySearchTree<Comparable>::BinarySearchTree( const Comparable & notFound ) :
root( NULL ), ITEM_NOT_FOUND( notFound )
{
}
/**
* Copy constructor.
*/
template <class Comparable>
BinarySearchTree<Comparable>::
BinarySearchTree( const BinarySearchTree<Comparable> & rhs ) :
root( NULL ), ITEM_NOT_FOUND( rhs.ITEM_NOT_FOUND )
{
*this = rhs;
}
/**
* Destructor for the tree.
*/
template <class Comparable>
BinarySearchTree<Comparable>::~BinarySearchTree( )
{
makeEmpty( );
}
/**
* Insert x into the tree; duplicates are ignored.
*/
template <class Comparable>
void BinarySearchTree<Comparable>::insert( const Comparable & x )
{
insert( x, root );
}
/**
* Remove x from the tree. Nothing is done if x is not found.
*/
template <class Comparable>
void BinarySearchTree<Comparable>::remove( const Comparable & x )
{
remove( x, root );
}
/**
* Find the smallest item in the tree.
* Return smallest item or ITEM_NOT_FOUND if empty.
*/
template <class Comparable>
const Comparable & BinarySearchTree<Comparable>::findMin( ) const
{
return elementAt( findMin( root ) );
}
/**
* Find the largest item in the tree.
* Return the largest item of ITEM_NOT_FOUND if empty.
*/
template <class Comparable>
const Comparable & BinarySearchTree<Comparable>::findMax( ) const
{
return elementAt( findMax( root ) );
}
/**
* Find item x in the tree.
* Return the matching item or ITEM_NOT_FOUND if not found.
*/
template <class Comparable>
const Comparable & BinarySearchTree<Comparable>::
find( const Comparable & x ) const
{
return elementAt( find( x, root ) );
}
/**
* Make the tree logically empty.
*/
template <class Comparable>
void BinarySearchTree<Comparable>::makeEmpty( )
{
makeEmpty( root );
}
/**
* Test if the tree is logically empty.
* Return true if empty, false otherwise.
*/
template <class Comparable>
bool BinarySearchTree<Comparable>::isEmpty( ) const
{
return root == NULL;
}
/**
* Print the tree contents in sorted order.
*/
template <class Comparable>
void BinarySearchTree<Comparable>::printTree( ) const
{
if( isEmpty( ) )
cout << "Empty tree" << endl;
else
printTree( root );
}
/**
* Deep copy.
*/
template <class Comparable>
const BinarySearchTree<Comparable> &
BinarySearchTree<Comparable>::
operator=( const BinarySearchTree<Comparable> & rhs )
{
if( this != &rhs )
{
makeEmpty( );
root = clone( rhs.root );
}
return *this;
}
/**
* Internal method to get element field in node t.
* Return the element field or ITEM_NOT_FOUND if t is NULL.
*/
template <class Comparable>
const Comparable & BinarySearchTree<Comparable>::
elementAt( BinaryNode<Comparable> *t ) const
{
if( t == NULL )
return ITEM_NOT_FOUND;
else
return t->element;
}
/**
* Internal method to insert into a subtree.
* x is the item to insert.
* t is the node that roots the tree.
* Set the new root.
*/
template <class Comparable>
void BinarySearchTree<Comparable>::
insert( const Comparable & x, BinaryNode<Comparable> * & t ) const
{
if( t == NULL )
t = new BinaryNode<Comparable>( x, NULL, NULL );
else if( x < t->element )
insert( x, t->left );
else if( t->element < x )
insert( x, t->right );
else
; // Duplicate; do nothing
}
/**
* Internal method to remove from a subtree.
* x is the item to remove.
* t is the node that roots the tree.
* Set the new root.
*/
template <class Comparable>
void BinarySearchTree<Comparable>::
remove( const Comparable & x, BinaryNode<Comparable> * & t ) const
{
if( t == NULL )
return; // Item not found; do nothing
if( x < t->element )
remove( x, t->left );
else if( t->element < x )
remove( x, t->right );
else if( t->left != NULL && t->right != NULL ) // Two children
{
t->element = findMin( t->right )->element;
remove( t->element, t->right );
}
else
{
BinaryNode<Comparable> *oldNode = t;
t = ( t->left != NULL ) ? t->left : t->right;
delete oldNode;
}
}
/**
* Internal method to find the smallest item in a subtree t.
* Return node containing the smallest item.
*/
template <class Comparable>
BinaryNode<Comparable> *
BinarySearchTree<Comparable>::findMin( BinaryNode<Comparable> *t ) const
{
if( t == NULL )
return NULL;
if( t->left == NULL )
return t;
return findMin( t->left );
}
/**
* Internal method to find the largest item in a subtree t.
* Return node containing the largest item.
*/
template <class Comparable>
BinaryNode<Comparable> *
BinarySearchTree<Comparable>::findMax( BinaryNode<Comparable> *t ) const
{
if( t != NULL )
while( t->right != NULL )
t = t->right;
return t;
}
/**
* Internal method to find an item in a subtree.
* x is item to search for.
* t is the node that roots the tree.
* Return node containing the matched item.
*/
template <class Comparable>
BinaryNode<Comparable> *
BinarySearchTree<Comparable>::
find( const Comparable & x, BinaryNode<Comparable> *t ) const
{
if( t == NULL )
return NULL;
else if( x < t->element )
return find( x, t->left );
else if( t->element < x )
return find( x, t->right );
else
return t; // Match
}
/****** NONRECURSIVE VERSION*************************
template <class Comparable>
BinaryNode<Comparable> *
BinarySearchTree<Comparable>::
find( const Comparable & x, BinaryNode<Comparable> *t ) const
{
while( t != NULL )
if( x < t->element )
t = t->left;
else if( t->element < x )
t = t->right;
else
return t; // Match
return NULL; // No match
}
*****************************************************/
/**
* Internal method to make subtree empty.
*/
template <class Comparable>
void BinarySearchTree<Comparable>::
makeEmpty( BinaryNode<Comparable> * & t ) const
{
if( t != NULL )
{
makeEmpty( t->left );
makeEmpty( t->right );
delete t;
}
t = NULL;
}
/**
* Internal method to print a subtree rooted at t in sorted order.
*/
template <class Comparable>
void BinarySearchTree<Comparable>::printTree( BinaryNode<Comparable> *t ) const
{
if( t != NULL )
{
printTree( t->left );
cout << t->element << endl;
printTree( t->right );
}
}
/**
* Internal method to clone subtree.
*/
template <class Comparable>
BinaryNode<Comparable> *
BinarySearchTree<Comparable>::clone( BinaryNode<Comparable> * t ) const
{
if( t == NULL )
return NULL;
else
return new BinaryNode<Comparable>( t->element, clone( t->left ), clone( t->right ) );
}
答案 0 :(得分：0)
要模板化一个类，您不必在.h文件中定义函数。您也无法在.cpp文件中定义它们。我一直这样做是通过像往常一样在.h文件中定义模板化的类。然后在.hpp文件中编写函数定义。
.h文件将按如下方式编写：
#ifndef MYCLASS_H
#define MYCLASS_H
template<typename T> class MyClass
{
public:
int MyFunction();
}
#include "MyClass.hpp"
#endif
确保将.hpp文件包含在.h文件中，而不是相反。
然后你的.hpp文件会是这样的：
template<typename T>
int MyClass::MyFunction()
{
...
}
确保使用该函数作范围，并且不要在.hpp中包含.h文件。编译器会生你的气。
这与定义.h文件中的函数基本相同，但这允许您保留两个单独的文件。如果你的课很小，功能很少，或者大部分功能都是一个衬里，即。 getter / setter函数。可能不值得为此制作一个完整的文件，但在像BST和AVL这样的情况下，拥有多个文件非常好，所以你不会盯着代码墙。