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我是一個非常困惑的學生。任何幫助你可以表示讚賞。我不確定如何爲模板類編寫此代碼。我不斷收到看起來像這樣一些奇怪的編譯錯誤：C++中的模板類 - 編寫鏈接列表開始的麻煩
g++ -c test_list.cpp
List.cpp: In constructor ‘cop4530::List<T>::iterator::iterator(cop4530::List<T>::Node*) [with T = int]’:
List.cpp:247: instantiated from ‘typename cop4530::List<T>::iterator cop4530::List<T>::begin() [with T = int]’
test_list.cpp:25: instantiated from here
List.cpp:112: error: invalid conversion from ‘cop4530::List<int>::Node*’ to ‘int’
List.cpp:112: error: initializing argument 1 of ‘cop4530::List<T>::Node::Node(const T&, cop4530::List<T>::Node*, cop4530::List<T>::Node*) [with T = int]’
List.cpp: In constructor ‘cop4530::List<T>::iterator::iterator(cop4530::List<T>::Node*) [with T = std::basic_string<char, std::char_traits<char>, std::allocator<char> >]’:
List.cpp:247: instantiated from ‘typename cop4530::List<T>::iterator cop4530::List<T>::begin() [with T = std::basic_string<char, std::char_traits<char>, std::allocator<char> >]’
test_list.cpp:134: instantiated from here
List.cpp:112: error: no match for ‘operator=’ in ‘*((cop4530::List<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >::iterator*)this)->cop4530::List<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >::iterator::<anonymous>.cop4530::List<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >::const_iterator::current = p’
List.h:11: note: candidates are: cop4530::List<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >::Node& cop4530::List<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >::Node::operator=(const cop4530::List<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >::Node&)
make: *** [test_list.o] Error 1
最重要的是 - 這裏是我試圖修復確切的代碼：
template <class T>
typename List<T>::iterator List<T>::begin()
{ // iterator to first element
if (!empty())
return iterator(head->next);
}
以下是完整的標題：
#ifndef DL_LIST_H
#define DL_LIST_H
#include <iostream>
namespace cop4530 {
template <typename T>
class List {
private:
// nested Node class
struct Node {
T data;
Node *prev;
Node *next;
Node(const T & d = T(), Node *p = NULL, Node *n = NULL)
: data(d), prev(p), next(n) {}
};
public:
//nested const_iterator class
class const_iterator {
public:
const_iterator(); // default zero parameter constructor
const T & operator*() const; // operator*() to return element
// increment/decrement operators
const_iterator & operator++();
const_iterator operator++(int);
const_iterator & operator--();
const_iterator operator--(int);
// comparison operators
bool operator==(const const_iterator &rhs) const;
bool operator!=(const const_iterator &rhs) const;
protected:
Node *current; // pointer to node in List
T & retrieve() const; // retrieve the element refers to
const_iterator(Node *p); // protected constructor
friend class List<T>;
};
// nested iterator class
class iterator : public const_iterator {
public:
iterator() {}
T & operator*();
const T & operator*() const;
// increment/decrement operators
iterator & operator++();
iterator operator++(int);
iterator & operator--();
iterator operator--(int);
protected:
iterator(Node *p);
friend class List<T>;
};
public:
// constructor, desctructor, copy constructor
List(); // default zero parameter constructor
List(const List &rhs); // copy constructor
// num elements with value of val
explicit List(int num, const T& val = T());
// constructs with elements [start, end)
List(const_iterator start, const_iterator end);
~List(); // destructor
// assignment operator
const List& operator=(const List &rhs);
// member functions
int size() const; // number of elements
bool empty() const; // check if list is empty
void clear(); // delete all elements
void reverse(); // reverse the order of the elements
T &front(); // reference to the first element
const T& front() const;
T &back(); // reference to the last element
const T & back() const;
void push_front(const T & val); // insert to the beginning
void push_back(const T & val); // insert to the end
void pop_front(); // delete first element
void pop_back(); // delete last element
void remove(const T &val); // remove all elements with value = val
// print out all elements. ofc is deliminitor
void print(std::ostream& os, char ofc = ' ') const;
iterator begin(); // iterator to first element
const_iterator begin() const;
iterator end(); // end marker iterator
const_iterator end() const;
iterator insert(iterator itr, const T& val); // insert val ahead of itr
iterator erase(iterator itr); // erase one element
iterator erase(iterator start, iterator end); // erase [start, end)
private:
int theSize; // number of elements
Node *head; // head node
Node *tail; // tail node
void init(); // initialization
};
// overloading comparison operators
template <typename T>
bool operator==(const List<T> & lhs, const List<T> &rhs);
template <typename T>
bool operator!=(const List<T> & lhs, const List<T> &rhs);
// overloading output operator
template <typename T>
std::ostream & operator<<(std::ostream &os, const List<T> &l);
// include the implementation file here
#include "List.cpp"
} // end of namespace 4530
#endif
這裏大部分的.cpp的：
using namespace std;
// --------------------- CONST_ITERATOR --------------------- //
template <class T>
List<T>::const_iterator::const_iterator()
{ // default zero-parameter constructor. Set pointer current to NULL.
current = NULL;
}
template <class T>
const T& List<T>::const_iterator::operator*() const
{ // returns a reference to the corresponding element in the list by calling retrieve() member function.
return retrieve();
}
template <class T>
typename List<T>::const_iterator& List<T>::const_iterator::operator++()
{
current = current->next;
return *this;
}
template <class T>
typename List<T>::const_iterator List<T>::const_iterator::operator++(int)
{
const_iterator old = *this;
++(*this);
return old;
}
template <class T>
typename List<T>::const_iterator& List<T>::const_iterator::operator--()
{
current = current->prev;
return *this;
}
template <class T>
typename List<T>::const_iterator List<T>::const_iterator::operator--(int)
{
const_iterator old = *this;
--(*this);
return old;
}
template <class T>
bool List<T>::const_iterator::operator==(const const_iterator &rhs) const
{return current == rhs.current;}
template <class T>
bool List<T>::const_iterator::operator!=(const const_iterator &rhs) const
{return !(*this == rhs);}
template <class T>
T& List<T>::const_iterator::retrieve() const
{ // return a reference to the corresponding element in the list.
return current->data;
}
template <class T>
List<T>::const_iterator::const_iterator(Node *p)
{ // one-parameter constructor
// Set pointer current to the given node pointer p.
current = p;
}
// --------------------- ITERATOR --------------------- //
template <typename T>
T& List<T>::iterator::operator*()
{
return List<T>::iterator::retrieve();
}
template <typename T>
const T& List<T>::iterator::operator*() const
{
return List<T>::iterator::retrieve();
}
template <class T>
typename List<T>::iterator& List<T>::iterator::operator++()
{
*this->current = *this->current->next;
return *this;
}
template <class T>
typename List<T>::iterator List<T>::iterator::operator++(int)
{
iterator old = *this;
++(*this);
return old;
}
template <class T>
typename List<T>::iterator& List<T>::iterator::operator--()
{
*this->current = *this->current->prev;
return *this;
}
template <class T>
typename List<T>::iterator List<T>::iterator::operator--(int)
{
iterator old = *this;
--(*this);
return old;
}
template <class T>
List<T>::iterator::iterator(Node *p)
{ // one-parameter constructor
// Set current to the given node pointer p
*this->current = p;
}
// --------------------- LIST --------------------- //
template <class T>
List<T>::List()
{ init(); }
template <class T>
List<T>::List(const List & rhs)
{ // Copy constructor
init();
*this = rhs;
}
template <class T>
List<T>::List(int num, const T& val)
{ //Constructs a list with num elements, all initialized with value val
init();
iterator itr = begin();
for (int i = 0; i < num; ++i)
{
insert(itr, val);
++itr;
}
}
template <class T>
List<T>::~List()
{ // Destructor
clear();
delete head;
delete tail;
}
template <class T>
const typename List<T>::List& List<T>::operator=(const List &rhs)
{ // Assignment operator
iterator ritr = rhs.first();
iterator itr = begin();
if(this != &rhs)
{
clear();
for(; ritr != NULL; ritr++, itr++)
insert(ritr.retrieve(), itr);
}
return *this;
}
template <class T>
int List<T>::size() const
{ // return the number of elements in the List
return theSize;
}
template <class T>
bool List<T>::empty() const
{ // check if list is empty
return head->next == NULL;
}
template <class T>
void List<T>::clear()
{ // delete all elements
while(!empty())
erase(begin());
}
template <class T>
T& List<T>::front()
{ // reference to the first element
return head->next->data;
}
template <class T>
typename List<T>::iterator List<T>::begin()
{ // iterator to first element
if (!empty())
return iterator(head->next);
}
template <class T>
typename List<T>::iterator List<T>::end()
{ // end marker iterator
if (!empty())
return iterator(tail->prev);
}
template <class T>
typename List<T>::iterator List<T>::insert(iterator itr, const T & x)
{
Node *p = itr.current;
theSize++;
return iterator(p->prev = p->prev->next = new Node(x, p->prev, p));
}
template <class T>
typename List<T>::iterator List<T>::erase(iterator itr)
{
Node *p = itr.current;
iterator retVal(p->next);
p->prev->next = p->next;
p->next->prev = p->prev;
delete p;
theSize--;
return retVal;
}
template <class T>
typename List<T>::iterator List<T>::erase(iterator start, iterator end)
{
for(iterator itr = start; itr != end;)
itr = erase(itr);
return end;
}
template <class T>
void List<T>::init()
{ // Initaialize the member variables of a List
theSize = 0;
head = new Node;
tail = new Node;
head->next = tail;
tail->prev = head;
}
讓我先告訴你（a）我知道他們在單獨的文件中，這對於類模板來說是一個很大的禁忌，但我不能在這個任務中改變它。 （b）這是作業。 （c）我已經嘗試了這段代碼的一些變體，它們沿着相同的方向獲取更多或更少的編譯錯誤。如果你幫助我，我會很開心......在這裏待了一兩個小時。
謝謝！如果您需要更多信息，請告訴我！
這是我原來的。現在我得到了新的編譯器錯誤，儘管少了它們。我編輯了上面的帖子，以反映新的編譯器錯誤（並且我將此更改添加到代碼中）。任何想法可以解決這個問題？ – jordaninternets 2012-02-08 02:58:49