Need some help fast with Template in Double Linked List

[Adryanmh]

Ok so i finally managed to finish a working DLL using only class...anyway now i have to use template. So here is what i tried:

#include <cstdlib>
#include <iostream>
using namespace std;
template <class Tip>
class nod{
      nod<Tip>* next;
      nod<Tip>* back;
      public:
             Tip x;
             nod(Tip a){back=NULL;x=a;next=NULL;}      
             friend class Lista;
             friend class ListaD;
      };     
template <class Tip>
class Lista{
public:
      nod<Tip>* first;
      nod<Tip>* last;
      Lista(){first=NULL;last=NULL;}       //-constructor
      Lista(Tip x){first=NULL;last=NULL;insert(x);}
      void creare();                       //Creates the list
      bool isEmpty(){return (first==NULL);}    //-Verifies if its empty
      virtual void insert(Tip x);   
      void afisare(){nod<Tip>* c;c=first;   while(c!=NULL){ cout<<c->x<<" ";c=c->next;} cout<<endl;} // Shows the whole list from right to left
      ~Lista();   //-destructor
};
template <class Tip>
void Lista<Tip>::creare()
{
 cout<<"How many elements should it contain? "<<endl;
 int n;
 Tip x;
 cin>>n;
 for(int i=1;i<=n;i++)
 {
 cout<<"Insert the element: (You have "<<(n-i+1)<<" elements left to insert)"<<endl;
 cin>>x;
 insert(x);
 }
}


template <class Tip>
void Lista<Tip>::insert(Tip x)
{

                   nod<Tip>* a=new nod<Tip>(x);
                   if(isEmpty())
                           {  first=a;
                              last=a;
                            }
                   else
                            {
                              last->next=a;
                              last=a;
                            }
                                                                 
}                      
template <class Tip>
Lista<Tip>::~Lista()
{
nod<Tip>* c;
               while(first!=NULL)
               {  
               c=first;
               first=first->next;
               delete c;               
               }
}


int main()

    Lista<int> A;
    return 0;
}

i get errors:

  In instantiation of `nod<int>': 
66 C:\Dev-Cpp\LP3 v2.cpp   instantiated from `Lista<Tip>::~Lista() [with Tip = int]' 
396 C:\Dev-Cpp\LP3 v2.cpp   instantiated from here 
9 C:\Dev-Cpp\LP3 v2.cpp template argument required for `struct Lista' 
 C:\Dev-Cpp\LP3 v2.cpp In destructor `Lista<Tip>::~Lista() [with Tip = int]': 
396 C:\Dev-Cpp\LP3 v2.cpp   instantiated from here 
6 C:\Dev-Cpp\LP3 v2.cpp `nod<int>*nod<int>::next' is private 
66 C:\Dev-Cpp\LP3 v2.cpp within this context 
 C:\Dev-Cpp\LP3 v2.cpp In member function `void Lista<Tip>::insert(Tip) [with Tip = int]': 
397 C:\Dev-Cpp\LP3 v2.cpp   instantiated from here 
6 C:\Dev-Cpp\LP3 v2.cpp `nod<int>*nod<int>::next' is private 
54 C:\Dev-Cpp\LP3 v2.cpp within this context 
  C:\Dev-Cpp\Makefile.win [Build Error]  ["LP3 v2.o"] Error 1   

Any help is appreciated.New to templates.(just 3 hours ago started reading about them)
Ty

[Adryanmh]

Its actually a simple linked list. I deleted the double linked list (its inherited). I want to make this one work for now...
If main is empty. i get no errors...>.<

[Zhuge]

On line 9, the first error is saying your friend declarations need to have be a template instantiation; i.e. you can't be a friend of Lista, you need to be a friend of Lista<int> or some other instance.

On line 54 and 66, the member 'first' is private and can't be accessed.

[Adryanmh]

Hmm, then how should i declare them friends? friend class<tip> Lista;
gives me " 'Lista' is not a template type ' " and some other errors.
And yes you are right with the private, Thank you! It works if i put public on all members. But how can i make it private and work? .
Thank you again
And one more question. With inheritance, should it work if i just add " template <class Tip>" like i did in this class?

[Adryanmh]

ok i managed somehow by declaring Lista as a template first row, now the next problem is how to declare a inheritance .
I declared it
template <class Tip>
class ListaD: public Lista<Tip> {


but i get error at the end " first is undeclared
last is undeclared " . If i declare
Class ListaD: public Lista<int> it works o.O

Edit: Even the overloading operators works,everything is fine now ,except that it only works with <int> and not <Tip> , so i can work only with integers..Can anyone please help me with this? The inherited class is not taking anything from the Lista. It acts like a independent. Even IsEmpty() isn't working.

[Adryanmh]

template <class Tip>
class ListaD : public Lista<Tip> {
      public:
      ListaD() : Lista<Tip>(){};
      void insert_back(Tip x);   
      void delete_last();  
      void delete_first();   
      void gasire_cheie(Tip k);    
      void delete_cheie(nod<Tip>* k);    
      void insert(Tip x);
       ~ListaD();
       ListaD& operator= (const ListaD &a);
       ListaD operator+ (const ListaD &a);
       ListaD(const ListaD &a)
       {
                   nod<Tip>* d = a.first ;
	               while(d!=NULL)
	               {
		           insert(d->x);
		           d=d->next;
	               }
       } 
      };
template <class Tip>
ListaD<Tip> & ListaD<Tip>::operator= (const ListaD & a)
{
	while(first!=NULL)
	{
		delete_first();
	}


	nod<Tip>* d = a.first ;
	while(d!=NULL)
	{
		insert(d->x);
		d=d->next;
	}

	return (*this) ;        
}
template <class Tip>

 
template <class Tip>
 ListaD<Tip> ListaD<Tip>::operator+ (const ListaD &a)
{
      ListaD art;
      nod<Tip>* c;
      nod<Tip>* d;
      Tip temp;
      d=a.first;
      c=first;
      while(c!=NULL && d!=NULL)
            {    
                
                 temp=((c->x)+(d->x));
                 art.insert(temp);
                 
            
            c=c->next;
            d=d->next;
            }
      return (art);
}
template <class Tip>
void ListaD<Tip>::delete_cheie(nod<Tip>* k)
{
      nod<Tip>* c;
      c=k->back;
      c->next=k->next;
      c=k->next;
      c->back=k->back;
      delete k;
}

template <class Tip>
void ListaD<Tip>::gasire_cheie(Tip k)
{
     nod<Tip>* c;
     nod<Tip>* p;
     int contur=0;
     c=first;
     while(c!=NULL)
     {
         if(k==c->x)
         {
         contur++;
         p=c;
              
         }
         c=c->next;
         
     }
     if(contur>1)
              {
              cout<<"In multimea exista "<<contur<<" elemente cu valoarea "<<k<<"."<<endl;
              cout<<"Pe al catelea doriti sa il stergeti?(Tastati 1,2,3...etc in functie de al catelea elem doriti)"<<endl;
              int choose;
              cin>>choose;
              while(choose<1 && choose>contur)
              {
              cout<<"Valoarea data nu exista!Reintroduceti!"<<endl;
              cin>>choose;
              }
              c=first;
                      while(c!=NULL)
                      { 
                                      if(k==c->x)
                                      {
                                                if(choose==1)
                                                {    
                                                     if(c!=last && c!=first)
                                                     {delete_cheie(c);}
                                                     else
                                                     {
                                                               if(c==last)
                                                               {
                                                               delete_last();
                                                               }
                                                               else
                                                               {
                                                               delete_first();
                                                               }
                                                     }
                                                     
                                                     break;
                                                }
                                                choose--;
                                      } 
                      c=c->next;
                      }
              }
     if(contur==1)
     {
                  if(p!=last && p!=first)
                  {
                  delete_cheie(p);
                  }
                  else
                  {
                      if(p==last)
                      {
                                 delete_last();
                      }
                      else
                      {
                         delete_first();
                      }
                  }
     }
     if(contur==0)
     {
     cout<<"Elementul cautat nu exista."<<endl;
     }
    
}

template <class Tip>
void ListaD<Tip>::insert_back(Tip x)
{
     nod<Tip>* a=new nod<Tip>(x);
                   if(isEmpty())
                            {  first=a;
                               last=a;
                            }
                   else 
                            {
                              first->back=a;
                              a->next=first;
                              first=a;
                            }
     
}

template <class Tip>
void ListaD<Tip>::delete_first()
{
              if(isEmpty())
              {
              cout<<"Eroare.Lista este goala."<<endl;             
              }
              else
              {
                  if(first->next==NULL)
                  {
                  delete first;
                  last=NULL;
                  first=NULL;
                   
                  }
                  else{
              nod<Tip>* c;
              c=first;
              first=first->next;
              first->back=NULL;    
              delete c;
              }
              }
}

template <class Tip>
void ListaD<Tip>::delete_last()
{
              if(isEmpty())
              {
              cout<<"Eroare.Lista este goala."<<endl;             
              }
              else
              {
                    if(last->back==NULL)
                    {
                    delete last;
                    last=NULL;
                    first=NULL;
                    }
                    else
                    {
                    nod<Tip>* c;
                    c=last;
                    last=last->back;
                    last->next=NULL;    
                    delete c;
                    }
              }
}

template <class Tip>
void ListaD<Tip>::insert(Tip x)
{

                   nod<Tip>* a=new nod<Tip>(x);
                   if(isEmpty())
                           {  first=a;
                              last=a;
                            }
                   else
                            {
                              last->next=a;
                              a->back=last;
                              last=a;
                            }
                                                                 
} 

template <class Tip>
ListaD<Tip>::~ListaD()
{
nod<Tip>* c;
               while(first!=NULL)
               {  
               c=first;
               first=first->next;
               delete c;               
               }
}

[clanmjc]

"Hmm, then how should i declare them friends? friend class<tip> Lista;
gives me " 'Lista' is not a template type ' " and some other errors."

Template friend class:
template <typename T> friend class Lista;

As for it only working for ints, I don't understand what you are saying completely. So this works...

ListaD<int> mylista;

But this doesn't??

ListaD<SomeClass> mylista;

What is confusing me is you are using the template type in your wording. Meaning, when you do ListaD<int>, where Tip = int. Are you truly saying you are doing ListaD<Tip>, where Tip = Tip?

Your declaration, see how this confuses the reader, can you elaborate or show how you are trying to instantiate the template as well as this "Tip" class?:

template <class Tip>
class ListaD : public Lista<Tip> {
      public:

[Adryanmh]

I just wanted a Double Linked List inherited(derived) from the Simple Linked List using only classes. And i wanted to switch int/float/double whenever i want. Exemple:
1st List: ListD <int>A;
2nd List: ListD <float>B; etc..
Doing operations and such (I'm aware that i must make only int + int (A+B) with this kind of code).
Anyway just one type everywhere. I managed to mae the friend class work. Thank you ^^. i was missing a piece of code at the beggining of the code:

template <class Tip>
class Lista;

(thats needed before declaring friend class, or else i get "Lista is not a template".
Now i don't get it. If i insert the code written above on my last post, it doesn't work and says:" first is undeclared.... last is undeclared,..... a function IsEmpty() is necessary..." things like that. If i put class ListaD : public Lista<int> { replacing Tip with int it works perfectly. For now i just declared nod<Tip> last, nod<Tip> first, afisare() and isEmpty(). But they should be already be declared, being a inherited class right? Also weird thing is that the only thing inherited is the citire() function. (It works only if i redeclare them)
Sorry for my bad english,i hope you understood.