Question

由于某些原因，我在编译代码时不断收到“模板agrument 1无效错误”。我不知道为什么。我正在尝试使用模板创建链接列表。这是我的代码

运行我的main方法时，我将类引入：

Dlist<L> list;

然后我尝试实现一些功能。

我得到的错误是：

 Dlist<L> list;  template agrument 1 is invalid. 

                      ^

HELP

ListNode.H

#ifndef LISTNODE_H
#define LISTNODE_H

#include <iostream>  
using namespace std;

template <class L>
class ListNode
{
    public:
    L data;
    ListNode *prev;
    ListNode *next;


    ListNode(L d);
    ListNode();
    ~ListNode();
};

template <class L>
ListNode<L>::ListNode()//blank constructor
{

}

template <class L> 
ListNode<L>::ListNode(L d)//overloaded constructor
{
    next = NULL;
    prev = NULL;
    data = d;
}

template <class L>
ListNode<L>::~ListNode()//deconstructor
{
    next = NULL;
    prev = NULL;
}

#endif

DList.h

#ifndef DLIST_H
#define DLIST_H

#include <iostream>
#include "ListNode.h"

using namespace std;

template <class L>
class Dlist
{
    private:
        ListNode<L>* front;
        ListNode<L>* back;
        unsigned int size;

    public:
        Dlist();//constructor
        ~Dlist();//destructor

        //insert and remove functions
        void insertFront(L data);
        int removeFront();
        void insertBack(L data);
        int removeBack();
        ListNode<L>* removeAt(L pos);

        //other functions
        bool isEmpty();
        int find(L val);
        int getFront();
        int getBack();
        unsigned int getSize();
        void printList();


};

template <class L>
Dlist<L>::Dlist()
{
    size = 0;
    front = NULL;
    back = NULL;
}

template <class L>
Dlist<L>::~Dlist()
{
    if(front != NULL)
    {
        delete front;
    }
}

template <class L>
void Dlist<L>::insertFront(L data)
{
    ListNode<L> *node = new ListNode<L>(data);
    if (size = 0)
    {
        back = node;
    }
    else
    {
        front->prev=node;
        node->next=front;
    }
    size++;
    front = node;
}

template <class L>
int Dlist<L>::removeFront()
{
    ListNode<L> *temp = front;
    if(front->next = NULL)
    {
        back = NULL;
    }
    else
    {
        front->next->prev = NULL;
        front->next = NULL;
    }
    front = front->next;
    int val = temp->data;
    delete temp;
    --size;
    return val;
}

template <class L>
void Dlist<L>::insertBack(L data)
{
    ListNode<L> *node = new ListNode<L>(data);
    if (size == 0)
    {
        front = node;
    }
    else
    {
        back->next = node;
        node->prev = back;
    }
    back = node;
    size++;
}

template <class L>
int Dlist<L>::removeBack()
{
    ListNode<L> *temp = back;
    if(back->prev = NULL)
    {
        front = NULL;
    }
    else
    {
        back->prev->next = NULL;
    }
    back = back->prev;
    int val = temp->data;
    delete temp;
    --size;
    return val;
}

template <class L>
ListNode<L>* Dlist<L>::removeAt(L key)
{
    ListNode<L>* curr = front;

    while(curr->data != key)
    {
        curr=curr->next;
        if (curr == NULL)
        {
            return NULL;
        }
    }
    //found the key
    if(curr == front)
    {
        front=curr->next;
}
    else
    {
        curr->prev->next = curr->next;
    }
    if(curr==back)
    {
        back = curr->prev;
    }
    else
    {
        curr->next->prev = curr->prev;
    }
    curr->next=NULL;
    curr->prev = NULL;
    size--;

    return curr;
}

template <class L>
unsigned int Dlist<L>::getSize()
{
    return size;
}

template <class L>
void Dlist<L>::printList()
{
    ListNode<L>* curr = front;

    while(curr != NULL)
    {
        cout<< curr->data << endl;
        curr = curr->next;
    }
}

template <class L>
int Dlist<L>::getFront()
{
    return front;
}

template <class L>
int Dlist<L>::getBack()
{
    return back;
}
#endif

Answer 1

你不能在尝试时使用模板类。

DLIST＆LT; L＆GT;列表;

由于L不是有效的数据类型。有效数据类型包括内置或用户定义的数据类型。＆＃34; L＆＃34;您正在将其用作模板，因此您只能在模板类中使用它。

如果您定义自己的班级，则上述声明有效。＆＃39; L＆＃39;如下所示：

class L
{
    int a;
};

希望有所帮助。

获取模板参数是无效错误？为什么？

1 个答案: