首先, 开门见山, 这个难题的解决办法是用this指针, 或者使用父类配合着scope resolution。 这个问题是我在学习linked list as an ADT , linked list 是含有纯虚函数, 所以是抽象基础类。 然后又linked list 继承出unordered linked list。 注意, 还可以
首先, 开门见山, 这个难题的解决办法是用this指针, 或者使用父类配合着scope resolution。
这个问题是我在学习linked list as an ADT , linked list 是含有纯虚函数, 所以是抽象基础类。 然后又linked list 继承出unordered linked list。 注意, 还可以由linked list 继承出ordered linked list。
言归正传, 出现问题的代码如下:
linkedlist.h 文件如下:
#ifndef H_LinkedListType #define H_LinkedListType #include <iostream> #include <cassert> using namespace std; //Definition of the node template <class type> struct nodeType { Type info; nodeType<type> *link; }; template <class type> class linkedListIterator { public: linkedListIterator(); //Default constructor //Postcondition: current = NULL; linkedListIterator(nodeType<type> *ptr); //Constructor with a parameter. //Postcondition: current = ptr; Type operator*(); //Function to overload the dereferencing operator *. //Postcondition: Returns the info contained in the node. linkedListIterator<type> operator++(); //Overload the pre-increment operator. //Postcondition: The iterator is advanced to the next // node. bool operator==(const linkedListIterator<type>& right) const; //Overload the equality operator. //Postcondition: Returns true if this iterator is equal to // the iterator specified by right, // otherwise it returns the value false. bool operator!=(const linkedListIterator<type>& right) const; //Overload the not equal to operator. //Postcondition: Returns true if this iterator is not // equal to the iterator specified by // right; otherwise it returns the value // false. private: nodeType<type> *current; //pointer to point to the current //node in the linked list }; template <class type> linkedListIterator<type>::linkedListIterator() { current = NULL; } template <class type> linkedListIterator<type>:: linkedListIterator(nodeType<type> *ptr) { current = ptr; } template <class type> Type linkedListIterator<type>::operator*() { return current->info; } template <class type> linkedListIterator<type> linkedListIterator<type>::operator++() { current = current->link; return *this; } template <class type> bool linkedListIterator<type>::operator== (const linkedListIterator<type>& right) const { return (current == right.current); } template <class type> bool linkedListIterator<type>::operator!= (const linkedListIterator<type>& right) const { return (current != right.current); } //***************** class linkedListType **************** template <class type> class linkedListType { public: const linkedListType<type>& operator= (const linkedListType<type>&); //Overload the assignment operator. void initializeList(); //Initialize the list to an empty state. //Postcondition: first = NULL, last = NULL, count = 0; bool isEmptyList() const; //Function to determine whether the list is empty. //Postcondition: Returns true if the list is empty, // otherwise it returns false. void print() const; //Function to output the data contained in each node. //Postcondition: none int length() const; //Function to return the number of nodes in the list. //Postcondition: The value of count is returned. void destroyList(); //Function to delete all the nodes from the list. //Postcondition: first = NULL, last = NULL, count = 0; Type front() const; //Function to return the first element of the list. //Precondition: The list must exist and must not be // empty. //Postcondition: If the list is empty, the program // terminates; otherwise, the first // element of the list is returned. Type back() const; //Function to return the last element of the list. //Precondition: The list must exist and must not be // empty. //Postcondition: If the list is empty, the program // terminates; otherwise, the last // element of the list is returned. virtual bool search(const Type& searchItem) const = 0; //Function to determine whether searchItem is in the list. //Postcondition: Returns true if searchItem is in the // list, otherwise the value false is // returned. virtual void insertFirst(const Type& newItem) = 0; //Function to insert newItem at the beginning of the list. //Postcondition: first points to the new list, newItem is // inserted at the beginning of the list, // last points to the last node in the list, // and count is incremented by 1. virtual void insertLast(const Type& newItem) = 0; //Function to insert newItem at the end of the list. //Postcondition: first points to the new list, newItem // is inserted at the end of the list, // last points to the last node in the list, // and count is incremented by 1. virtual void deleteNode(const Type& deleteItem) = 0; //Function to delete deleteItem from the list. //Postcondition: If found, the node containing // deleteItem is deleted from the list. // first points to the first node, last // points to the last node of the updated // list, and count is decremented by 1. linkedListIterator<type> begin(); //Function to return an iterator at the begining of the //linked list. //Postcondition: Returns an iterator such that current is // set to first. linkedListIterator<type> end(); //Function to return an iterator one element past the //last element of the linked list. //Postcondition: Returns an iterator such that current is // set to NULL. linkedListType(); //default constructor //Initializes the list to an empty state. //Postcondition: first = NULL, last = NULL, count = 0; linkedListType(const linkedListType<type>& otherList); //copy constructor ~linkedListType(); //destructor //Deletes all the nodes from the list. //Postcondition: The list object is destroyed. protected: int count; //variable to store the number of //elements in the list nodeType<type> *first; //pointer to the first node of the list nodeType<type> *last; //pointer to the last node of the list private: void copyList(const linkedListType<type>& otherList); //Function to make a copy of otherList. //Postcondition: A copy of otherList is created and // assigned to this list. }; template <class type> bool linkedListType<type>::isEmptyList() const { return(first == NULL); } template <class type> linkedListType<type>::linkedListType() //default constructor { first = NULL; last = NULL; count = 0; } template <class type> void linkedListType<type>::destroyList() { nodeType<type> *temp; //pointer to deallocate the memory //occupied by the node while (first != NULL) //while there are nodes in the list { temp = first; //set temp to the current node first = first->link; //advance first to the next node delete temp; //deallocate the memory occupied by temp } last = NULL; //initialize last to NULL; first has already //been set to NULL by the while loop count = 0; } template <class type> void linkedListType<type>::initializeList() { destroyList(); //if the list has any nodes, delete them } template <class type> void linkedListType<type>::print() const { nodeType<type> *current; //pointer to traverse the list current = first; //set current so that it points to //the first node while (current != NULL) //while more data to print { cout info link; } }//end print template <class type> int linkedListType<type>::length() const { return count; } //end length template <class type> Type linkedListType<type>::front() const { assert(first != NULL); return first->info; //return the info of the first node }//end front template <class type> Type linkedListType<type>::back() const { assert(last != NULL); return last->info; //return the info of the last node }//end back template <class type> linkedListIterator<type> linkedListType<type>::begin() { linkedListIterator<type> temp(first); return temp; } template <class type> linkedListIterator<type> linkedListType<type>::end() { linkedListIterator<type> temp(NULL); return temp; } template <class type> void linkedListType<type>::copyList (const linkedListType<type>& otherList) { nodeType<type> *newNode; //pointer to create a node nodeType<type> *current; //pointer to traverse the list if (first != NULL) //if the list is nonempty, make it empty destroyList(); if (otherList.first == NULL) //otherList is empty { first = NULL; last = NULL; count = 0; } else { current = otherList.first; //current points to the //list to be copied count = otherList.count; //copy the first node first = new nodeType<type>; //create the node first->info = current->info; //copy the info first->link = NULL; //set the link field of //the node to NULL last = first; //make last point to the //first node current = current->link; //make current point to //the next node //copy the remaining list while (current != NULL) { newNode = new nodeType<type>; //create a node newNode->info = current->info; //copy the info newNode->link = NULL; //set the link of //newNode to NULL last->link = newNode; //attach newNode after last last = newNode; //make last point to //the actual last node current = current->link; //make current point //to the next node }//end while }//end else }//end copyList template <class type> linkedListType<type>::~linkedListType() //destructor { destroyList(); }//end destructor template <class type> linkedListType<type>::linkedListType (const linkedListType<type>& otherList) { first = NULL; copyList(otherList); }//end copy constructor //overload the assignment operator template <class type> const linkedListType<type>& linkedListType<type>::operator= (const linkedListType<type>& otherList) { if (this != &otherList) //avoid self-copy { copyList(otherList); }//end else return *this; } #endif </type></type></type></class></type></type></class></type></class></type></type></type></type></type></type></class></type></type></type></class></type></type></type></class></type></class></type></class></type></class></type></type></class></type></class></type></type></class></type></class></type></class></type></type></type></type></type></type></type></type></class></type></type></class></type></type></class></type></type></class></type></class></type></type></class></type></class></type></type></type></type></type></class></type></class></cassert></iostream>
unorderedLinkedList.h文件如下:
#ifndef H_UnorderedLinkedList #define H_UnorderedLinkedList #include "linkedList.h" using namespace std; template <class type> class unorderedLinkedList: public linkedListType<type> { public: bool search(const Type& searchItem) const; //Function to determine whether searchItem is in the list. //Postcondition: Returns true if searchItem is in the // list, otherwise the value false is // returned. void insertFirst(const Type& newItem); //Function to insert newItem at the beginning of the list. //Postcondition: first points to the new list, newItem is // inserted at the beginning of the list, // last points to the last node in the // list, and count is incremented by 1. void insertLast(const Type& newItem); //Function to insert newItem at the end of the list. //Postcondition: first points to the new list, newItem // is inserted at the end of the list, // last points to the last node in the // list, and count is incremented by 1. void deleteNode(const Type& deleteItem); //Function to delete deleteItem from the list. //Postcondition: If found, the node containing // deleteItem is deleted from the list. // first points to the first node, last // points to the last node of the updated // list, and count is decremented by 1. }; template <class type> bool unorderedLinkedList<type>:: search(const Type& searchItem) const { nodeType<type> *current; //pointer to traverse the list bool found = false; current = first; //set current to point to the first //node in the list while (current != NULL && !found) //search the list if (current->info == searchItem) //searchItem is found found = true; else current = current->link; //make current point to //the next node return found; }//end search template <class type> void unorderedLinkedList<type>::insertFirst(const Type& newItem) { nodeType<type> *newNode; //pointer to create the new node newNode = new nodeType<type>; //create the new node newNode->info = newItem; //store the new item in the node newNode->link = this -> first; //insert newNode before first first = newNode; //make first point to the //actual first node count++; //increment count if (last == NULL) //if the list was empty, newNode is also //the last node in the list last = newNode; }//end insertFirst template <class type> void unorderedLinkedList<type>::insertLast(const Type& newItem) { nodeType<type> *newNode; //pointer to create the new node newNode = new nodeType<type>; //create the new node newNode->info = newItem; //store the new item in the node newNode->link = NULL; //set the link field of newNode //to NULL if ( first == NULL) //if the list is empty, newNode is //both the first and last node { first = newNode; last = newNode; count++; //increment count } else //the list is not empty, insert newNode after last { last->link = newNode; //insert newNode after last last = newNode; //make last point to the actual //last node in the list count++; //increment count } }//end insertLast template <class type> void unorderedLinkedList<type>::deleteNode(const Type& deleteItem) { nodeType<type> *current; //pointer to traverse the list nodeType<type> *trailCurrent; //pointer just before current bool found; if (first == NULL) //Case 1; the list is empty. cout info == deleteItem) //Case 2 { current = first; first = first->link; count--; if (first == NULL) //the list has only one node last = NULL; delete current; } else //search the list for the node with the given info { found = false; trailCurrent = first; //set trailCurrent to point //to the first node current = first->link; //set current to point to //the second node while (current != NULL && !found) { if (current->info != deleteItem) { trailCurrent = current; current = current-> link; } else found = true; }//end while if (found) //Case 3; if found, delete the node { trailCurrent->link = current->link; this -> count--; if (last == current) //node to be deleted //was the last node last = trailCurrent; //update the value //of last delete current; //delete the node from the list } else cout <br> 主程序如下main.cpp: <pre class="brush:php;toolbar:false">//This program tests various operation of a linked list //34 62 21 90 66 53 88 24 10 -999 #include <iostream> #include "unorderedLinkedList.h" using namespace std; int main() { unorderedLinkedList<int> list1, list2; //Line 1 int num; //Line 2 cout > num; //Line 4 while (num != -999) //Line 5 { list1.insertLast(num); //Line 6 cin >> num; //Line 7 } cout > num; //Line 19 cout it; //Line 27 for (it = list1.begin(); it != list1.end(); ++it) //Line 28 cout <br> 编译结果error message 如下: <p><img src="/static/imghwm/default1.png" data-src="/inc/test.jsp?url=http%3A%2F%2Fimg.blog.csdn.net%2F20140730194616575%3Fwatermark%2F2%2Ftext%2FaHR0cDovL2Jsb2cuY3Nkbi5uZXQvYTEzMDczNw%3D%3D%2Ffont%2F5a6L5L2T%2Ffontsize%2F400%2Ffill%2FI0JBQkFCMA%3D%3D%2Fdissolve%2F70%2Fgravity%2FSouthEast&refer=http%3A%2F%2Fblog.csdn.net%2Fa130737%2Farticle%2Fdetails%2F38305293" class="lazy" alt="C++ 关于模板之间的继承, 导致的模板子类的成员看不到(cannot" ><br> </p> <p><br> </p> <p>错误分析: 按照标准看, 上述的错误似乎有点问题。 因为first, last, count 都是父类的成员变量。 存取类型是protected。 我们的子类unorderedLinkedList 类是公开方式(public)继承linkedList。按说子类即unorderedLinkedList 的成员函数(虚函数)当然可以access 父类的protected 成员变量。 但是在这里出错了。 为什么呢?</p> <p><br> </p> <p>原因是我们这里是模板类之间的继承。 如果是正常的普通类之间的继承, 结果一定是没有问题的。 当然access会通过, 编译会okay。 但是这里是模本类之间的继承。</p> <p>在这里, 我们需要使用this 指针, 也可以使用scope resolution解决模板类之间的继承时变量访问的问题。 下面我们修改unorderedLinkedList.h 如下:</p> <p>将模板成员函数定义count, first, last 分别用this -> count, this -> first, this -> last(第二中解决办法是换为linkedListType<type>::first, linkedListType<type>::count,linkedListType<type>::last)。 不光如此, 当在子类中调用模板父类的成员函数的时候, 也要使用this 指针或者用scope resotion 解决这个问题。</type></type></type></p> <p><br> </p> <pre class="brush:php;toolbar:false">#ifndef H_UnorderedLinkedList #define H_UnorderedLinkedList #include "linkedList.h" using namespace std; template <class type> class unorderedLinkedList: public linkedListType<type> { public: bool search(const Type& searchItem) const; //Function to determine whether searchItem is in the list. //Postcondition: Returns true if searchItem is in the // list, otherwise the value false is // returned. void insertFirst(const Type& newItem); //Function to insert newItem at the beginning of the list. //Postcondition: first points to the new list, newItem is // inserted at the beginning of the list, // last points to the last node in the // list, and count is incremented by 1. void insertLast(const Type& newItem); //Function to insert newItem at the end of the list. //Postcondition: first points to the new list, newItem // is inserted at the end of the list, // last points to the last node in the // list, and count is incremented by 1. void deleteNode(const Type& deleteItem); //Function to delete deleteItem from the list. //Postcondition: If found, the node containing // deleteItem is deleted from the list. // first points to the first node, last // points to the last node of the updated // list, and count is decremented by 1. }; template <class type> bool unorderedLinkedList<type>:: search(const Type& searchItem) const { nodeType<type> *current; //pointer to traverse the list bool found = false; current = this -> first; //set current to point to the first //node in the list while (current != NULL && !found) //search the list if (current->info == searchItem) //searchItem is found found = true; else current = current->link; //make current point to //the next node return found; }//end search template <class type> void unorderedLinkedList<type>::insertFirst(const Type& newItem) { nodeType<type> *newNode; //pointer to create the new node newNode = new nodeType<type>; //create the new node newNode->info = newItem; //store the new item in the node newNode->link = this -> first; //insert newNode before first this -> first = newNode; //make first point to the //actual first node this -> count++; //increment count if (this -> last == NULL) //if the list was empty, newNode is also //the last node in the list this -> last = newNode; }//end insertFirst template <class type> void unorderedLinkedList<type>::insertLast(const Type& newItem) { nodeType<type> *newNode; //pointer to create the new node newNode = new nodeType<type>; //create the new node newNode->info = newItem; //store the new item in the node newNode->link = NULL; //set the link field of newNode //to NULL if ( this -> first == NULL) //if the list is empty, newNode is //both the first and last node { this -> first = newNode; this -> last = newNode; this -> count++; //increment count } else //the list is not empty, insert newNode after last { this -> last->link = newNode; //insert newNode after last this -> last = newNode; //make last point to the actual //last node in the list this -> count++; //increment count } }//end insertLast template <class type> void unorderedLinkedList<type>::deleteNode(const Type& deleteItem) { nodeType<type> *current; //pointer to traverse the list nodeType<type> *trailCurrent; //pointer just before current bool found; if (this -> first == NULL) //Case 1; the list is empty. cout first->info == deleteItem) //Case 2 { current = this -> first; this -> first = this -> first->link; this -> count--; if (this -> first == NULL) //the list has only one node this -> last = NULL; delete current; } else //search the list for the node with the given info { found = false; trailCurrent = this -> first; //set trailCurrent to point //to the first node current = this -> first->link; //set current to point to //the second node while (current != NULL && !found) { if (current->info != deleteItem) { trailCurrent = current; current = current-> link; } else found = true; }//end while if (found) //Case 3; if found, delete the node { trailCurrent->link = current->link; this -> count--; if (this -> last == current) //node to be deleted //was the last node this -> last = trailCurrent; //update the value //of last delete current; //delete the node from the list } else cout <br> 编译通过, 运行结果如下: <p><img src="/static/imghwm/default1.png" data-src="/inc/test.jsp?url=http%3A%2F%2Fimg.blog.csdn.net%2F20140730200300296%3Fwatermark%2F2%2Ftext%2FaHR0cDovL2Jsb2cuY3Nkbi5uZXQvYTEzMDczNw%3D%3D%2Ffont%2F5a6L5L2T%2Ffontsize%2F400%2Ffill%2FI0JBQkFCMA%3D%3D%2Fdissolve%2F70%2Fgravity%2FSouthEast&refer=http%3A%2F%2Fblog.csdn.net%2Fa130737%2Farticle%2Fdetails%2F38305293" class="lazy" alt="C++ 关于模板之间的继承, 导致的模板子类的成员看不到(cannot" ><br> </p> <p><br> </p> <p><br> </p> <p>关于这个模板继承, 子类使用父类的成员是使用this, 或者scope resolution, 解释如下:</p> <p>//To make the code valid either use this->f(), or Base::f(). Using the -fpermissive flag will also<br> //let the compiler accept the code, by marking all function calls for which no declaration is visible<br> //at the time of definition of the template for later lookup at instantiation time, as if it were a<br> //dependent call. We do not recommend using -fpermissive to work around invalid code, and it will also<br> //only catch cases where functions in base classes are called, not where variables in base classes are<br> //used (as in the example above).<br> //<br> //Note that some compilers (including G++ versions prior to 3.4) get these examples wrong and accept above<br> //code without an error. Those compilers do not implement two-stage name lookup correctly.<br> //<br> </p> <p><br> </p> <p>接下来是我在stack overflow 网站上得到的解答:</p> <p><img src="/static/imghwm/default1.png" data-src="/inc/test.jsp?url=http%3A%2F%2Fimg.blog.csdn.net%2F20140730201910930%3Fwatermark%2F2%2Ftext%2FaHR0cDovL2Jsb2cuY3Nkbi5uZXQvYTEzMDczNw%3D%3D%2Ffont%2F5a6L5L2T%2Ffontsize%2F400%2Ffill%2FI0JBQkFCMA%3D%3D%2Fdissolve%2F70%2Fgravity%2FSouthEast&refer=http%3A%2F%2Fblog.csdn.net%2Fa130737%2Farticle%2Fdetails%2F38305293" class="lazy" alt="C++ 关于模板之间的继承, 导致的模板子类的成员看不到(cannot" ><br> </p> </type></type></type></class></type></type></type></class></type></type></type></class></type></type></class></type></class>

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SecLists
SecLists是最終安全測試人員的伙伴。它是一個包含各種類型清單的集合,這些清單在安全評估過程中經常使用,而且都在一個地方。 SecLists透過方便地提供安全測試人員可能需要的所有列表,幫助提高安全測試的效率和生產力。清單類型包括使用者名稱、密碼、URL、模糊測試有效載荷、敏感資料模式、Web shell等等。測試人員只需將此儲存庫拉到新的測試機上,他就可以存取所需的每種類型的清單。

Dreamweaver Mac版
視覺化網頁開發工具

MinGW - Minimalist GNU for Windows
這個專案正在遷移到osdn.net/projects/mingw的過程中,你可以繼續在那裡關注我們。 MinGW:GNU編譯器集合(GCC)的本機Windows移植版本,可自由分發的導入函式庫和用於建置本機Windows應用程式的頭檔;包括對MSVC執行時間的擴展,以支援C99功能。 MinGW的所有軟體都可以在64位元Windows平台上運作。

VSCode Windows 64位元 下載
微軟推出的免費、功能強大的一款IDE編輯器

EditPlus 中文破解版
體積小,語法高亮,不支援程式碼提示功能