c++,templates,visual-studio-2012,linked-list , << Definition using inheritance and templates [duplicate]


<< Definition using inheritance and templates [duplicate]

Question:

Tag: c++,templates,visual-studio-2012,linked-list

This question already has an answer here:

I am trying to implement a Linked List in C++ using templates. Unfortunately I am getting an unresolved external error when I try to use a ostream. Solutions of similar questions on this site said it was because of a mismatch in the header file and the .cpp file, but I don't think it is the case here. Can anyone help me with this, I really need to grasp this.

LinkedList.h:

#ifndef LINKEDLIST_H
#define LINKEDLIST_H

#include <string>
#include <iostream>

template<class T> class LinkedList;

// Class representing a templated linkedlist element
template<class T> class LLElement {
    friend class LinkedList<T>;
public:
    // Constructor
    LLElement(T* p_Data) : data(p_Data), next(NULL) {}

    T* getData() const { return data; }
    LLElement<T>* getNext() { return next; }
private:
    LLElement<T>* next;
    T* data;
};

// Class representing a templated linked list
template<class T> class LinkedList {
public:
    LinkedList() : size(0), start(NULL) {}
    LinkedList(const LinkedList&);
    ~LinkedList();

    unsigned int getSize() const { return size; }
    LLElement<T>* getStart() const { return start; }

    //adds shallow copy of T to the LinkedList
    void sortedAdd(T*);
    //removes the first occurence of T from the LinkedList
    void remove(T*);
    //merges existing LinkedList with given LinkedList
    void merge(const LinkedList<T>&);
    //formatted print of LinkedList to given outputstream
    void showLinkedList(std::ostream& p_Out) const;
    friend std::ostream& operator<<(std::ostream& outputStream, const LinkedList<T>& sec);

private:
    LLElement<T>* start;
    unsigned int size;
};

//LinkedList copy constructor
//TODO
template<class T>  LinkedList<T>::LinkedList(const LinkedList<T>& a){
    this->size=a.getSize();
    this->start=a.getStart();
}

// LinkedList destructor
// TODO
template<class T> LinkedList<T>::~LinkedList(){
    LLElement<T>* a=this->getStart();
    LLElement<T>* b=a->next;
    while(a!=NULL){
        delete a;
        a=b;
        b=a->next;
    }

}


// sortedAdd
// adds shallow copy of T to the LinkedList
// TODO
template<class T> void LinkedList<T>::sortedAdd(T* add){
    LLElement<T>* a=new LLElement<T>(add);
    LLElement<T>* b=this->getStart();
    while(!(*(b->data)<=*(a->getData()))){
        b=b->next;
    }
    a->next=b->next;
    b->next=a;
    this->size++;
}



// remove
// removes the first occurence of T from the LinkedList
// TODO
template<class T> void LinkedList<T>::remove(T* ab){
    LLElement<T>* a=this->getStart();
    LLElement<T>* b=this->getStart();
    while(a!=NULL){
        if(*(a->data)==*(ab)){
            if(b==a){
                this->start=a->next;
                delete a;
                this->size--;
                return;
            }
            b->next=a->next;
            delete a;
            this->size--;
            return;
        }
        b=a;
        a=b->getNext();
    }
}


// TODO output operator

template<class T>  std::ostream& operator<<(std::ostream& outputStream, const LinkedList<T>& sec){
    sec.showLinkedList(outputStream);
    return outputStream;
}
//merges existing LinkedList with given LinkedList
template<class T> void LinkedList<T>::merge(const LinkedList<T>& p_LL){
    LLElement<T> *cursor = p_LL.start;
    while (cursor != NULL){
        sortedAdd(cursor->data);
        cursor = cursor->next;
    }
}

//formatted print of LinkedList to given outputstream
template<class T> void LinkedList<T>::showLinkedList(std::ostream& p_Out) const {
    LLElement<T>* current = start;
    int counter = 1;
    p_Out << "LINKEDLIST OF SIZE " << size << std::endl;
    while (current != NULL){
        p_Out << "LL ELEMENT " << counter++ << " : ";
        p_Out << *(current->getData()) << std::endl;
        current = current->getNext();
    }
}

#endif

Error:

Error   2   error LNK2019: unresolved external symbol "class
std::basic_ostream<char,struct std::char_traits<char> > & __cdecl
operator<<(class std::basic_ostream<char,struct std::char_traits<char> > &,class
LinkedList<class CMSContent> const &)" ([email protected][email protected]
[email protected]@[email protected]@@[email protected]@[email protected][email protected]@@@@@Z) referenced in function "public: void __thiscall CMS::print(void)" ([email protected]@@QAEXXZ)   C:\Users\knudde\Documents\Visual Studio 2012\Projects\Ex1314\Ex1314\CMS.obj Ex1314

Maybe there is a problem with the CMSContent?

Content.h:

#ifndef H_CONTENT
#define H_CONTENT

#include <map>
#include <set>
#include <iostream>
#include <string>

enum ACCESSRIGHT { owner, modify, read, none };

class CMSContent {
public:
    CMSContent(std::string p_Id, std::string p_Username);

    void addPermissionUser(ACCESSRIGHT p_Right, std::string p_Username);
    ACCESSRIGHT getAccessright(std::string p_Username);

    std::string getIdentifier(){ return identifier; };
    virtual std::string serialise() const=0;
    bool CMSContent::operator< (const CMSContent& param) const;
    bool CMSContent::operator<= (const CMSContent& param) const;
    bool CMSContent::operator== (const CMSContent& param) const;
    friend std::ostream& operator<<(std::ostream& outputStream, CMSContent& secondOperand);
protected:
    std::string identifier;
    std::map<ACCESSRIGHT, std::set<std::string> > accessrightsByRank;
    //map with key accessright and value set of usernames with given access right
private:
    void setIdentifier(std::string p_Id){ identifier = p_Id; };
    bool userHasHigherAccessRight(ACCESSRIGHT p_Right, std::string p_Username);
    void removeLowerAccessRights(ACCESSRIGHT p_Right, std::string p_Username);

    static int uniqueID;
};

class Project : public CMSContent {
public:
    Project(std::string p_Name, std::string p_Description, std::string p_Username);

    virtual std::string serialise() const;

    std::string getProjectdescription(){ return projectdescription; };
    void setProjectdescription(std::string p_Description){ projectdescription = p_Description; };
protected:
    std::string projectdescription;
};

class Document : public CMSContent {
public:
    Document(std::string p_Name, std::string p_Username, std::string p_URL);
    virtual std::string serialise() const;

    std::string getURL(){ return URL; };
    void setURL(std::string p_Url){ URL = p_Url; };
protected:
    std::string URL;
};

class HowTo : public CMSContent {
public:
    HowTo(std::string p_Subject, std::string p_Howto_content, std::string p_Username);
    virtual std::string serialise() const;

    std::string getHowto_content() { return howto_content; }
    void setHowto_content(std::string p_Howto_content) { howto_content = p_Howto_content; }
protected:
    std::string howto_content;
};

#endif

Content.cpp:

#include "Content.h"
#include <sstream>

CMSContent::CMSContent(std::string p_Id, std::string p_Username) : identifier(p_Id){
    accessrightsByRank[owner].insert(p_Username); 
}

void CMSContent::addPermissionUser(ACCESSRIGHT right, std::string p_Username) { 
    if (!userHasHigherAccessRight(right, p_Username)){
        removeLowerAccessRights(right, p_Username);
        accessrightsByRank[right].insert(p_Username);
    }
}

bool CMSContent::operator< (const CMSContent& param) const{
    return (this->identifier.compare(param.identifier)<0);
}

bool CMSContent::operator<= (const CMSContent& param) const{
    return (this->identifier.compare(param.identifier)<=0);
}

bool CMSContent::operator== (const CMSContent& param) const{
    return (this->identifier.compare(param.identifier)==0);
}

std::ostream& operator<<(std::ostream& outputStream,  CMSContent& cont){
    outputStream<<cont.serialise();
    outputStream<<"owner = ";
    std::set<std::string>::iterator a,b;
    a=cont.accessrightsByRank[owner].begin();
    b=cont.accessrightsByRank[owner].end();
    while(a!=b){
        outputStream << (*a) <<std::endl;
    }
        outputStream<<"modify = ";

    a=cont.accessrightsByRank[modify].begin();
    b=cont.accessrightsByRank[modify].end();
    while(a!=b){
        outputStream << (*a) <<std::endl;
    }
    outputStream<<"read = ";

    a=cont.accessrightsByRank[read].begin();
    b=cont.accessrightsByRank[read].end();
    while(a!=b){
        outputStream << (*a) <<std::endl;
    }
    return outputStream;
}

bool CMSContent::userHasHigherAccessRight(ACCESSRIGHT right, std::string p_Username){
    //TODO
    if(right==owner){return false;}
    std::map<ACCESSRIGHT, std::set<std::string> >::iterator beg, end;
    std::set<std::string> ::iterator beg1, end1;
    beg=accessrightsByRank.begin();
    end=accessrightsByRank.find(right);
    while(beg != end){
        beg1=(*beg).second.begin();
        end1=(*beg).second.end();
        while(beg1!=end1){
            if((*beg1).compare(p_Username)==0){
                return true;
            }
            beg1++;
        }
        beg++;
    }
    return false;
}

void CMSContent::removeLowerAccessRights(ACCESSRIGHT right, std::string p_Username){
    //TODO
    std::map<ACCESSRIGHT, std::set<std::string> >::iterator beg, end;
    std::set<std::string> ::iterator beg1, end1;
    end=accessrightsByRank.end();
    beg=accessrightsByRank.find(right)++;
    while(beg != end){
        beg1=(*beg).second.begin();
        end1=(*beg).second.end();
        while(beg1!=end1){
            if((*beg1).compare(p_Username)==0){
                (*beg).second.erase(beg1);
                return;
            }
            beg1++;
        }
        beg++;
    }
}

Project::Project(std::string p_Identifier, std::string p_Description, std::string p_Username) : CMSContent("P;"+p_Identifier, p_Username){
    projectdescription = p_Description; 
}

std::string Project::serialise() const {
    std::stringstream output;
    output << "Project name = " << identifier << std::endl;
    output << "Project description = " << projectdescription << std::endl;
    return output.str();
}

Document::Document(std::string p_Identifier, std::string p_Username, std::string p_URL) : CMSContent("D;"+p_Identifier, p_Username){ 
    URL = p_URL;
}

std::string Document::serialise() const {
    std::stringstream output;
    output << "Document name = " << identifier << std::endl;
    output << "Document URL = " << URL << std::endl;
    return output.str();
}

HowTo::HowTo(std::string p_Identifier, std::string p_Howto_content, std::string p_Username) : CMSContent("H;"+p_Identifier, p_Username){ 
    howto_content = p_Howto_content; 
}

std::string HowTo::serialise() const{
    std::stringstream output;
    output << "Howto subject = " << identifier << std::endl;
    output << "Howto content = " << howto_content << std::endl;
    return output.str();
}

Answer:

Remove friend std::ostream& operator<<(std::ostream& outputStream, const LinkedList<T>& sec); from LinkedList class definition. You already have a templated version of such operator in this header, and linker tells that non-templated one is lacking implementation. LinkedList.h:

#ifndef LINKEDLIST_H
#define LINKEDLIST_H

#include <string>
#include <iostream>

template<class T> class LinkedList;

// Class representing a templated linkedlist element
template<class T> class LLElement {
    friend class LinkedList<T>;
public:
    // Constructor
    LLElement(T* p_Data) : data(p_Data), next(NULL) {}

    T* getData() const { return data; }
    LLElement<T>* getNext() { return next; }
private:
    LLElement<T>* next;
    T* data;
};

// Class representing a templated linked list
template<class T> class LinkedList {
public:
    LinkedList() : size(0), start(NULL) {}
    LinkedList(const LinkedList&);
    ~LinkedList();

    unsigned int getSize() const { return size; }
    LLElement<T>* getStart() const { return start; }

    //adds shallow copy of T to the LinkedList
    void sortedAdd(T*);
    //removes the first occurence of T from the LinkedList
    void remove(T*);
    //merges existing LinkedList with given LinkedList
    void merge(const LinkedList<T>&);
    //formatted print of LinkedList to given outputstream
    void showLinkedList(std::ostream& p_Out) const;
    //friend std::ostream& operator<<(std::ostream& outputStream, const LinkedList<T>& sec);

private:
    LLElement<T>* start;
    unsigned int size;
};

//LinkedList copy constructor
//TODO
template<class T>  LinkedList<T>::LinkedList(const LinkedList<T>& a){
    this->size=a.getSize();
    this->start=a.getStart();
}

// LinkedList destructor
// TODO
template<class T> LinkedList<T>::~LinkedList(){
    LLElement<T>* a=this->getStart();
    LLElement<T>* b=a->next;
    while(a!=NULL){
        delete a;
        a=b;
        b=a->next;
    }

}


// sortedAdd
// adds shallow copy of T to the LinkedList
// TODO
template<class T> void LinkedList<T>::sortedAdd(T* add){
    LLElement<T>* a=new LLElement<T>(add);
    LLElement<T>* b=this->getStart();
    while(!(*(b->data)<=*(a->getData()))){
        b=b->next;
    }
    a->next=b->next;
    b->next=a;
    this->size++;
}



// remove
// removes the first occurence of T from the LinkedList
// TODO
template<class T> void LinkedList<T>::remove(T* ab){
    LLElement<T>* a=this->getStart();
    LLElement<T>* b=this->getStart();
    while(a!=NULL){
        if(*(a->data)==*(ab)){
            if(b==a){
                this->start=a->next;
                delete a;
                this->size--;
                return;
            }
            b->next=a->next;
            delete a;
            this->size--;
            return;
        }
        b=a;
        a=b->getNext();
    }
}


// TODO output operator

template<class T>  std::ostream& operator<<(std::ostream& outputStream, const LinkedList<T>& sec){
    sec.showLinkedList(outputStream);
    return outputStream;
}
//merges existing LinkedList with given LinkedList
template<class T> void LinkedList<T>::merge(const LinkedList<T>& p_LL){
    LLElement<T> *cursor = p_LL.start;
    while (cursor != NULL){
        sortedAdd(cursor->data);
        cursor = cursor->next;
    }
}

//formatted print of LinkedList to given outputstream
template<class T> void LinkedList<T>::showLinkedList(std::ostream& p_Out) const {
    LLElement<T>* current = start;
    int counter = 1;
    p_Out << "LINKEDLIST OF SIZE " << size << std::endl;
    while (current != NULL){
        p_Out << "LL ELEMENT " << counter++ << " : ";
        p_Out << *(current->getData()) << std::endl;
        current = current->getNext();
    }
}

#endif

Also, regarding Content.h:

bool CMSContent::operator< (const CMSContent& param) const;
bool CMSContent::operator<= (const CMSContent& param) const;
bool CMSContent::operator== (const CMSContent& param) const;

should be

bool operator< (const CMSContent& param) const;
bool operator<= (const CMSContent& param) const;
bool operator== (const CMSContent& param) const;

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email,templates,go,mandrill
I am sending mail to users via mandrill and I using both smtp and mandrill api to send. Content of the mail is rendered go template (.tpl) When I put template like Hi {{.name}}, <br/> This is support. <br/> it sends via mandrill api ok, but is visible when I...

Get an ordered list of files in a folder


c++,boost,boost-filesystem
I have used boost::filesystem::directory_iterator in order to get a list of all the available files into a given folder. The problem is that I supposed this method would give me the files in alphabetical order, while the results seem pretty random. Is there any fancy way of alphabetically sorting them?...

Marshal struct in struct from c# to c++


c#,c++,marshalling
I have the following structures in C# and C++. C++: struct TestA { char* iu; }; struct TestB { int cycle1; int cycle2; }; struct MainStruct { TestA test; TestB test2; }; C#: [StructLayout(LayoutKind.Sequential, CharSet=CharSet.Ansi, Pack = 1)] internal struct TestA { [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 36)] private string iu; public...

std::condition_variable – notify once but wait thread wakened twice


c++,multithreading
Here's a simple C++ thread pool implementation. It's an altered version orginated from https://github.com/progschj/ThreadPool. #ifndef __THREAD_POOL_H__ #define __THREAD_POOL_H__ #include <vector> #include <queue> #include <memory> #include <thread> #include <chrono> #include <mutex> #include <condition_variable> #include <future> #include <functional> #include <stdexcept> namespace ThreadPool { class FixedThreadPool { public: FixedThreadPool(size_t); template<class F, class......

Issue when use two type-cast operators in template class


c++
I define a template class in which, I define two type-cast operator template <class base_t> struct subclass { base_t base; //any function which defined for 'base_t' can be used with 'subclass<base_t>' operator base_t&() { return base; } //I want 'subclass<base_t>' can be converted to any class which 'base_t' can //I...

Explicit instantiation of class template not instantiating constructor


c++,templates,constructor,explicit-instantiation
I'm working on a project in C++ and am having trouble understanding what members of a template class get explicitly instantiated when I explicitly instantiate the template class. I've written the following file, which I then compile using Visual C++ 2008 Express Edition's Release configuration and then pop into a...

Confused about returns in stack template


c++,templates,generic-programming
I'm implementing a generic stack (with an array) in C++ and am confused about what to return in this situation: template <class T> T Stack<T>::pop(void) { if (size != 0) { return items[size - 1]; size--; } else { cerr << "Cannot pop from empty stack." << endl; return ???;...

C++ & Qt: Random string from an array area


c++,arrays,string,qt,random
In my small Qt application, I want to pick a random string out of an array after I clicked on a button. I've read many threads but nothing works for me. So in my slot there's an array with several strings in it. I also implemented <string>, <time.h> and srand....

How can I tell clang-format to follow this convention?


c++,clang-format
I would like to have this: if (!enabled) { return; } turned to this: if (!enabled) { return; } (In other words, I want short if-statements on a single line but keep the {} around them) Currently I'm using the following configuration: AllowShortIfStatementsOnASingleLine: true AllowShortLoopsOnASingleLine: true AllowShortCaseLabelsOnASingleLine: true AllowShortFunctionsOnASingleLine: true...

Incorrect Polar - Cartesian Coordinate Conversions. What does -0 Mean?


c++,polar-coordinates,cartesian-coordinates
I am getting incorrect conversions from polar to cartesian coordinates and vice versa. My code produces weird points like (1,-0). Im using this calculator to check my conversions. Also one of the conversions is completely wrong when I convert back to cartesian coordinates. Point b: (0,1) => (1,1.5708) => (0,0)...

C++11 Allocation Requirement on Strings


c++,string,c++11,memory,standards
I had heard that C++11 was going to require strings to be allocated in contiguous memory. I even thought I saw a stack overflow question on it, but I can't seem to find it. I know that in practice both gcc and Visual Studio do allocate strings contiguously, I'm just...

Validate case pattern (isupper/islower) on user input string


c++,user-input
I need to write a program that checks if the user-provided first and last names are correctly typed. The program needs to validate that only the first letter of each name part is uppercase. I managed to write code that checks the first character of the input. So I have...

C++ template template


c++,templates
I'm trying to understand C++ template templates by implementing a generic container class. Here is the code: using namespace std; template <typename T, template <typename STORETYPE> class Container> class Store { public: ~Store() {}; Store() {}; void someFunc( const T & ) {}; //... private: Container<T> storage; }; int main(int...

3 X 3 magic square recursively


c++,algorithm,math,recursion
I'm trying to find all possible solutions to the 3X3 magic square. There should be exactly 8 solutions. My code gets them all but there are a lot of repeats. I'm having a hard time tracking the recursive steps to see why I'm getting all the repeats. // This program...

ctypes error AttributeError symbol not found, OS X 10.7.5


python,c++,ctypes
I have a simple test function on C++: #include <stdio.h> #include <string.h> #include <stdlib.h> #include <locale.h> #include <wchar.h> char fun() { printf( "%i", 12 ); return 'y'; } compiling: gcc -o test.so -shared -fPIC test.cpp and using it in python with ctypes: from ctypes import cdll from ctypes import c_char_p...