templates - C++ Custom List Iterator Errors -

i have started writing own library common data structures, educational purposes (ie: personal practice). however, encountered few problems cannot seem resolve myself on singly linked list. not c++ expert , code may have problems, please don't harsh on me :)

i have tried implement list_node class declares , defines node list, list_iterator class acts forward iterator singly linked list requires, list class supposed give make use of mentioned classes , provide functionality list.

i attach code , errors under visual studio.

list_node.h

/**  *  list_node.h  *  *  @author raul butuc.  *  @version 1.0.0 16/03/2015  */  #pragma once  #include "list.h" #include "list_iterator.h"  namespace my_library {    template <class _tp>   class list_node {      friend class list<_tp>;     friend class list_iterator<_tp>;      private:       _tp m_node;       list_node<_tp> *m_pnext;        list_node(const _tp&, list_node<_tp>*);       ~list_node();   };    template <class _tp>   list_node<_tp>::list_node(const _tp& node, list_node<_tp>* next) : m_node(node), m_pnext(next) {}    template <class _tp>   list_node<_tp>::~list_node() {     delete m_pnext;   }  } 

list_iterator.h

/**  *  list_iterator.h  *  *  @author raul butuc.  *  @version 1.0.0 16/03/2015  */  #pragma once  #include <cassert> #include <iterator> #include "list.h" #include "list_node.h"  namespace my_library {    template <class _tp> class list;   template <class _tp> class list_node;    template <class _tp>   class list_iterator {      public:       // line below has error c2059: syntax error : '<'       // error c2238: unexpected token(s) preceding ';'        friend class list<_tp>;       typedef list_iterator<_tp> iterator;       typedef size_t size_type;       typedef _tp value_type;       typedef _tp& reference;       typedef _tp* pointer;       typedef std::forward_iterator_tag iterator_category;       typedef int difference_type;        const iterator& operator++();       const iterator& operator++(int);       reference operator*();       pointer operator->();       bool operator==(const iterator&) const;       bool operator!=(const iterator&) const;      private:       list_node<_tp>* m_pnode;       list_iterator(list_node<_tp>*);    };    template <class _tp>   list_iterator<_tp>::list_iterator(list_node<_tp>* pnode) : m_pnode(pnode) {}    template <class _tp>   const list_iterator<_tp>::iterator& list_iterator<_tp>::operator++() {     assert(m_pnode != null);     m_pnode = m_pnode->m_pnext;     return *this;   }    template <class _tp>   const list_iterator<_tp>::iterator& list_iterator<_tp>::operator++(int) {     list_iterator<_tp>::iterator _tmp = *this;     ++(*this);     return _tmp;   }    template <class _tp>   list_iterator<_tp>::reference list_iterator<_tp>::operator*() {     return m_pnode->m_node;   }    template <class _tp>   list_iterator<_tp>::pointer list_iterator<_tp>::operator->() {     return m_pnode;   }    template <class _tp>   bool list_iterator<_tp>::operator==(const list_iterator<_tp>::iterator& other) const {     return m_pnode == other->m_pnode;   }    template <class _tp>   bool list_iterator<_tp>::operator!=(const list_iterator<_tp>::iterator& other) const {     return m_pnode != other->m_pnode;   }  } 

list.h

/**  *  list.h  *  *  @author raul butuc.  *  @version 1.0.0 16/03/2015  */  #pragma once  #include "list_node.h" #include "list_iterator.h"  namespace my_library {    template <class _tp>   class list {      public:       typedef list_iterator<_tp> iterator;        list();       ~list();        bool empty() const;       void push_back(const _tp&);        iterator begin();       iterator end();      private:       list_node<_tp>* m_phead;       list_node<_tp>* m_ptail;   };    template <class _tp>   list<_tp>::list() : m_phead(null), m_ptail(null) {}    template <class _tp>   list<_tp>::~list() {     delete m_phead;   }    template <class _tp>   bool list<_tp>::empty() const {     return m_phead == null;   }    template <class _tp>   void list<_tp>::push_back(const _tp& node) {     list_node<_tp>* _node = new list_node<_tp>(node, null);     if (m_phead == null) {       m_phead = _node;     }     else {       m_ptail->m_pnext = _node;     }     m_ptail = _node;   }    template <class _tp>   list<_tp>::iterator list<_tp>::begin() {     return list_iterator<_tp>(m_phead);   }    template <class _tp>   list<_tp>::iterator list<_tp>::end() {     return list_iterator<_tp>(null);   }  } 

test.cpp

/**  *  test.cpp  *  *  @author raul butuc.  *  @version 1.0.0 16/03/2015  */  #include <iostream> #include "list.h"  using std::cout; using namespace my_library;  int main(int argc, char* argv[]) {   list<int> list;    if (list.empty()) {     std::cout << "list empty" << "\n";   }    (int = 0; < 100; += 10) {     list.push_back(i);   }    // here should allow me write like:   // list<int>::iterator = list.begin();   // however, not. please explain   // why so? sorry if due naive mistake   // trying learn. again :)   list_iterator<int> = list.begin();    (; != list.end(); ++it) {     std::cout << *it << " ";   }   std::cout << "\n";    system("pause");   return 0; } 

errors @ compilation

1>------ build started: project: list, configuration: debug win32 ------
1> test.cpp
1>d:...\list_iterator.h(23): error c2059: syntax error : '<'
1>\d:...\list_iterator.h(43) : see reference class template instantiation 'my_library::list_iterator<_tp>' being compiled
1>d:...\list_iterator.h(23): error c2238: unexpected token(s) preceding ';'
1>d:...\list_iterator.h(40): error c2143: syntax error : missing ';' before '<'
1>d:...\list_iterator.h(40): error c4430: missing type specifier - int assumed. note: c++ not support default-int
1>d:...\list_iterator.h(40): error c2238: unexpected token(s) preceding ';'
1>d:...\list_iterator.h(41): error c2061: syntax error : identifier 'list_node'
1>d:...\list_iterator.h(46): error c2061: syntax error : identifier 'list_node'
1>d:...\list_iterator.h(49): warning c4346: 'my_library::list_iterator<_tp>::iterator' : dependent name not type
1> prefix 'typename' indicate type
1>d:...\list_iterator.h(49): error c2143: syntax error : missing ';' before '&'
1>d:...\list_iterator.h(49): error c2065: '_tp' : undeclared identifier
1>d:...\list_iterator.h(49): error c2923: 'my_library::list_iterator' : '_tp' not valid template type argument parameter '_tp'
1>d:...\list_iterator.h(53): error c2509: '++' : member function not declared in 'my_library::list_iterator'
1>
d:...\list_iterator.h(18) : see declaration of 'my_library::list_iterator'
1>d:...\list_iterator.h(53): fatal error c1903: unable recover previous error(s); stopping compilation
========== build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

thank taking time!

edit:

thanks mebob, indeed main problem. however, after fixing that, errors on line 52 , 56 in list_iterator.h:

1>d:\programming - data structures\list\list\list_iterator.h(52): warning c4346: 'my_library::list_iterator::iterator' : dependent name not type
1> prefix 'typename' indicate type
1>d:\programming - data structures\list\list\list_iterator.h(52): error c2143: syntax error : missing ';' before '&'
1>d:\programming - data structures\list\list\list_iterator.h(52): error c2065: 't' : undeclared identifier
1>d:\programming - data structures\list\list\list_iterator.h(52): error c2923: 'my_library::list_iterator' : 't' not valid template type argument parameter 't'
1>d:\programming - data structures\list\list\list_iterator.h(56): error c2509: '++' : member function not declared in 'my_library::list_iterator'
1>
d:\programming - data structures\list\list\list_iterator.h(21) : see declaration of 'my_library::list_iterator'
1>d:\programming - data structures\list\list\list_iterator.h(56): fatal error c1903: unable recover previous error(s); stopping compilation

i changed _tp t in classes (in code, didn't update here)

edit 2:

even after getting on errors, seems won't compile, time because of operators.

the code directly involved is:

  // other code...   template <class _tp>   typename list_iterator<_tp>::pointer list_iterator<_tp>::operator->() {     return m_pnode;   }    template <class _tp>   bool list_iterator<_tp>::operator==(const typename list_iterator<_tp>::iterator& other) const {     /*  error c2678: binary '->' : no operator found takes left-hand operand       of type 'const my_library::list_iterator<_tp>' (or there no acceptable conversion) */     return m_pnode == other->m_pnode;   }   // other code... 

from list_iterator.h

you must have forward declarations, so:

template <class _tp> class list; template <class _tp> class list_iterator; 

before friend declarations because otherwise, when compiler sees friend class list doesn't know expect template argument list.

as other error, must use const typename list_iterator<_tp>::iterator& type. time refer type that's member of templated class (or struct) must use typename keyword beforehand clarify compiler expecting type.

your last error because attempting call non-const operator->() on const. fix create const version of returns const pointer.

also, neil kirk commented, _tp reserved identifier shouldn't using that.