/in/foo.cc: In member function 'void IntLinkList::Append(int)':
/in/foo.cc:92:3: error: 'i' was not declared in this scope
   i->next = ntail;
   ^
/in/foo.cc: In member function 'void IntLinkList::InsertAt(int, int)':
/in/foo.cc:106:18: error: 'i' was not declared in this scope
    nnode->next = i;
                  ^
/in/foo.cc:110:7: error: 'i' was not declared in this scope
   if (i->next == NULL)//如果要插入尾结点
       ^
/in/foo.cc:115:17: error: 'i' was not declared in this scope
   nnode->next = i->next;//链接插入的结点和k号结点
                 ^
/in/foo.cc: In function 'int main(int, char**)':
/in/foo.cc:135:7: error: 'i' was not declared in this scope
  for (i = 0; i < n; i++)
       ^