Question

Im making a generic linked list.

I cant figure out how to make an object of my class from main.

My 3 files are main.cpp dan.h dan.cpp

The error is: 15 6 [Error] prototype for 'void ll<T>::insert()' does not match any in class 'll<T>'

#include <iostream>

#include <string>

#include "dan.h"

using namespace std;

int main()

{

ll<int> work;

work.insert(55);//THIS IS THE LINE THATS GIVING ME THE ERROR, Without this line it compiles and //runs.

}

#ifndef DAN_H

#define DAN_H

#include <iostream>

#include <string>

using namespace std;

template<class T>

struct node

{

T data;

node *next;

};

template <class T>

class ll

{

public:

ll();

void insert(T item);

void print();

private:

node<T> head;

int len;

node<T> cur;

};

#endif

#include <iostream>

#include <string>

#include "dan.h"

using namespace std;

template <class T>

ll<T>::ll()

{

head=NULL;

cur=NULL;

len=0;

}

template <class T>

void ll<T>::insert(T item)

{

node<T> temp;

temp->data=item;

if(head==NULL)

{

head=temp;

head->next=NULL;

}

else

{

temp->next=head;

head=temp;

}

}

template <class T>

void ll<T>::print()

{

node<T> temp=head;

while(temp!=NULL)

{

cout<<temp->data<<endl;

temp=temp->next;

}

}

Answer 1

/* NOTE:

Templates need to be declared and implemented in the file you include. You cannot separate template class declaration and implementation and then only include the header file.

With templates, the class is not compiled until it's used. So there is no such thing as a compiled template class that can be linked against. Each time you use a template, it has to be compiled for a different type. And since the compiler does not have access to the implementation, it does not know how to compile it... */

/* SO, SOLUTION IS TO INCLUDE BOTH header and implementation file in main.cpp */

/* main.cpp */

#include <iostream>

#include <string>

#include "dan.h"
#include "dan.cpp"

using namespace std;

int main()

{

ll<int> work;
work.insert(55);
work.print();
}

#include <iostream> #include <string> #include "dan.h" #include "dan.cpp" using namespace std; int main() 11<int> work; work.insert(55); work.print();

/*dan.h */

#ifndef DAN_H

#define DAN_H

#include <iostream>

#include <string>

using namespace std;

template<class T>

struct node

{

T data;

node<T> *next;

};

template <class T>

class ll

{

public:

ll();

void insert(T item);

void print();

private:

node<T> *head;

int len;

node<T> *cur;

};

#endif

#ifndef DAN_H #define DAN_H #include <iostream> #include <string> using namespace std; template<class T> struct node I data; node<T> *next; template <class T> class 11 public: 11(); void insert(T item); void print(); private: node<T> *head; int len; node<T> *cur; }; #endif

/* dan.cpp */

#include"dan.h"
template <class T>
ll<T>::ll()
{
head=NULL;
cur=NULL;
len=0;

}

template <class T>

void ll<T>::insert(T item)

{

node<T> *temp = new node<T>();

temp->data=item;

if(head==NULL)

{

head=temp;

head->next=NULL;

}

else

{

temp->next=head;

head=temp;

}

}

template <class T>

void ll<T>::print()

{

node<T> *temp=head;

while(temp!=NULL)

{

cout<<temp->data<<endl;

temp=temp->next;

}

}

#include" dan.h" template <class T> 11<T>::11) head=NULL; cur=NULL; len=0; template <class T> void 1l<T>::insert(T item) node<T> *temp = new node<T>(); // use new to create object temp->data=item; if(head==NULL) head=temp; head->next=NULL; else temp->next=head; head=temp;

template <class T> void ll<T>:: print) node<T> *temp=head; while(temp!=NULL) cout<<temp->data<<endl; temp=temp->next;

/* OUTPUT */

55 Process exited after 3.538 seconds with return value o Press any key to continue ...