일반적인 데이터 구조 list template

#include<iostream>
using namespace std;

template<typename T> 
struct Node{
       Node(T& d):c(d),next(0),pref(0){}
       T c;
       Node *next,*pref;
       };
       
template<typename T>
class List{
      Node<T> *first,*last;
public:
       List();
       void add(T& c);
       void remove(T& c);
       Node<T>* find(T& c);
       void print();
       ~List();
      };
template<typename T>
List<T>::List():first(0),last(0){}

template<typename T>
void List<T>::add(T& n){
     Node<T>* p=new Node<T>(n);
     p->next=first;
     first=p;
     (last ? p->next->pref : last)=p;
     }
template<typename T>
void List<T>::remove(T& n){
     Node<T>* p=find(n);
     if(!p)  return;
     (p->next?p->next->pref:last)=p->pref;
     (p->pref?p->pref->next:first)=p->next;
     delete p;
     }

template<typename T>
Node<T>* List<T>::find(T& n){
         for(Node<T>* p=first;p;p=p->next)
            if(p->c==n)  return p;
         return 0;
         }
template<typename T>
List<T>::~List(){
                 for(Node<T>* p;p=first;delete p)
                    first=first->next;
                 }
template<typename T>
void List<T>::print(){
     for(Node<T>* p=first;p;p=p->next)
        cout<<p->c<<"  ";
     cout<<"
";
     }
     


int main(int argc, char *argv[])
{
    //    template List<double>;
//    template List<int>;
    List<double> dList;
    double input1 = 3.6;
    double input2 = 5.8;
    dList.add(input1);
    dList.add(input2);
    dList.print();
    
    List<int> iList;
    int n1 = 5;
    int n2 = 8;
    iList.add(n1);
    iList.add(n2);

    iList.print();
    
    return 0;
}