麻烦各位帮忙看看，哪错了，该怎么修改


#include <iostream>
using namespace std;
struct node
{
 int data;
 struct node *next;
};

class list
{
private:
    node *head;
    node *tail;
    int length;
public:
    list()
    {head=NULL;tail=NULL;}

    void insert(int x)
    {
        
      if(head=new node)  cout<<"this is a new list"<<endl;
      
      node *p;
      p=new node;
      p->next=NULL;
      p->data=x;
      if(p->data==NULL) cout<<"error"<<endl;
     if(head->next==NULL)
        head=p;
     else

         tail->next=p;
     tail=p;
     length++;
     }

    void put()
    {
        node *q;
        q=new node;
        q->next=NULL;
        if(head->next=NULL)  cout<<"error"<<endl;
        while(!head->next)
        {
          cout<<q->data<<endl;

          q=q->next;
        }
          cout<<length<<endl;
     }
      ~list()
      {  node *q=NULL;
        while(head)
        {
           q=head;
           head=head->next;
           delete q;        
        }
        head=NULL;
        tail=NULL;            
      }   

};

void main()
{
   list obj1;
   int x;
   cout<<"print x"<<endl;
   cin>>x;
   obj1.insert(x);
   obj1.put();
}

[ 本帖最后由 ou1111 于 2010-10-29 12:58 编辑 ]

失误，不小心把一括号删了，这里的问题是运行不对，调试中显示          cout<<q->data<<endl;
这句有问题，该怎么改呀

[ 本帖最后由 ou1111 于 2010-10-29 12:56 编辑 ]

非常感谢，我刚学C++，懂得好少