c++ - syntax error while returning nested class of a template -

i have following class declaration:

template <typename key_t, typename mapped_t, size_t maxlevel = 5> class skiplist {  public:    class iterator   {     typedef std::pair<key_t, mapped_t> valuetype;     template <typename key1, typename obj1, size_t maxlevel1> friend class skiplist;     public:       //iterator functions      private:       //iterator data   };    skiplist();   ~skiplist();   skiplist(const skiplist &);   skiplist &operator=(const skiplist &);    std::pair<iterator, bool> insert(const valuetype &);   template <typename it_t>   void insert(it_t range_beg, it_t range_end);    void erase(iterator pos);   private:   //data }; 

when declaring skiplist insert function outside class definition

template <typename key_t, typename mapped_t, size_t maxlevel> typename std::pair<skiplist<key_t,mapped_t,maxlevel>::iterator, bool>  skiplist<key_t,mapped_t,maxlevel>::insert(const valuetype &input) 

the following error comes:

skiplist.cpp:349:69: error: type/value mismatch @ argument 1 in template parameter list ‘template<class _t1, class _t2> struct std::pair’ skiplist.cpp:349:69: error:   expected type, got ‘skiplist<key_t, mapped_t, maxlevel>::iterator’ skiplist.cpp:349:72: error: ‘skiplist’ in namespace ‘std’ not name type skiplist.cpp:349:80: error: expected unqualified-id before ‘<’ token 

what wrong code?

you need typename keyword:

typename std::pair<typename skiplist<key_t,mapped_t,maxlevel>::iterator, bool>  skiplist<key_t,mapped_t,maxlevel>::insert(const valuetype &input) 

or else compiler thinks iterator class member.