Question

这是我制作的快速模板Dequeue对象，它在mac终端上工作正常但是visual c ++对我来说不起作用。如果这是一个愚蠢的问题，请提前抱歉，我对C ++和模板有点新鲜。这是代码：

#include <iostream>
using namespace std;

template <typename T>
class Dequeue;

template <typename T>
class node;

template <typename T>
ostream& operator<<(ostream&, const Dequeue<T>&);

template <typename T>
class node{
public:
    node<T>* next;
    node<T>* prev;
    T data;
    node(T data=T(), node<T>* next=NULL, node<T>* prev=NULL);
};

template <typename T>
node<T>::node(T _data, node<T>* _next, node<T>* _prev){
    data = _data;
    next = _next;
    prev = _prev;
}

template <typename T>
class Dequeue{
private:
    node<T>* head;
    node<T>* tail;
    int _size;
    void clear();
public:
    Dequeue();
    ~Dequeue();
    Dequeue(const Dequeue<T>&);
    const Dequeue<T>& operator=(const Dequeue<T>&);
    friend ostream& operator<< <>(ostream&, Dequeue<T>&);
    void push_front(T&);
    void push_back(T&);
    void pop_front();
    void pop_back();
    T front();
    T back();
    int size();
    bool isEmpty();
};

template <typename T>
Dequeue<T>::Dequeue(){
    _size = 0;
    head = NULL;
    tail = NULL;
}

template <typename T>
Dequeue<T>::~Dequeue(){
    clear();
}

template <typename T>
void Dequeue<T>::clear(){
    while(_size > 0)
        pop_front();
}

template <typename T>
Dequeue<T>::Dequeue(const Dequeue<T>& other){
    head = NULL;
    tail = NULL;
    _size = 0;

    *this = other;
}

template <typename T>
const Dequeue<T>& Dequeue<T>::operator=(const Dequeue<T>& other){
    if(this = &other)
        return *this;
    clear();
    node<T>* np = other.head;
    while(np!=NULL){
        node<T>* p = new node<T>(np->data);

        if(head == tail == NULL)
            head = tail = p;

        else{
            tail->next = p;
            p->prev = tail;
        }

        tail = p;
        np = np->next;
    }

    _size = other._size;
    return *this;
}

template <typename T>
ostream& operator<<(ostream& out_str, Dequeue<T>& other){
    node<T>* np = other.head;

    while(np != NULL){
        out_str << np->data << endl;
        np = np->next;
    }
    return out_str;
}

template <typename T>
void Dequeue<T>::push_front(T& object){
    node<T>* np = new node<T>(object);

    np->next = head;
    head->prev = np;
    head = np;

    _size++;
}

template <typename T>
void Dequeue<T>::push_back(T& object){
    node<T>* np = new node<T>(object);

    tail->next = np;
    np->prev = tail;
    tail = np;

    _size++;
}

template <typename T>
void Dequeue<T>::pop_front(){
    node<T>* np = head;
    head = head->next;
    delete np;
    head->prev=NULL;

    _size--;
}

template <typename T>
void Dequeue<T>::pop_back(){
    node<T>* np = tail;
    tail = np->prev;
    delete np;
    tail->next = NULL;

    size--;
}

template <typename T>
T Dequeue<T>::front(){
    return head->data;
}

template <typename T>
T Dequeue<T>::back(){
    return tail->data;
}

template <typename T>
int Dequeue<T>::size(){
    return _size;
}

template <typename T>
bool Dequeue<T>::isEmpty(){
    if(size == 0)
        return true;
    else
        return false;
}

int main(){
    Dequeue<int> A;

    A.push_back(5);
    A.push_front(6);
    A.push_back(7);

    cout << A << endl;

    cin.get();
    return 0;
}

以下是我得到的错误：

1>------ Build started: Project: Kevin, Configuration: Debug Win32 ------
1>  Dequeue.cpp
1>c:\users\kevin nguyen\documents\visual studio 2010\projects\kevin\kevin\dequeue.cpp(184): error C2664: 'Dequeue<T>::push_back' : cannot convert parameter 1 from 'int' to 'int &'
1>          with
1>          [
1>              T=int
1>          ]
1>c:\users\kevin nguyen\documents\visual studio 2010\projects\kevin\kevin\dequeue.cpp(185): error C2664: 'Dequeue<T>::push_front' : cannot convert parameter 1 from 'int' to 'int &'
1>          with
1>          [
1>              T=int
1>          ]
1>c:\users\kevin nguyen\documents\visual studio 2010\projects\kevin\kevin\dequeue.cpp(186): error C2664: 'Dequeue<T>::push_back' : cannot convert parameter 1 from 'int' to 'int &'
1>          with
1>          [
1>              T=int
1>          ]
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

Answer 1

您的问题是，在您的声明中，您试图引用T。在这种情况下，您传入函数的文字（例如A.push_back(5)）不一定是可以参考的文字。您的声明应该看起来更像这样：

/* use `const` */
void Dequeue<T>::push_front( const T& object )
/* Same for push_back: use `const` */
void Dequeue<T>::push_back( const T& object )

Const将允许您传递常量数据作为参考。无论如何你都要复制它，所以如果他们正在参考，请确保你的所有声明一直使用const。

此外，最好不要将节点中的T data参数默认为新创建的T。这将强制您使用链接列表的任何数据类型具有默认构造函数。只需改为const T& data，或者根本不使用T。

Visual C ++不会让我使用模板？

1 个答案: