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Question

I have the following classes and I am trying to overload the operator* from the inner class iterator

#ifndef __LISTMAP_H__
#define __LISTMAP_H__

#include "xless.h"
#include "xpair.h"

template <typename Key, typename Value, class Less=xless<Key>>
class listmap {
   public:
      using key_type = Key;
      using mapped_type = Value;
      using value_type = xpair<const key_type, mapped_type>;
   private:
      Less less;
      struct node;
      struct link {
         node* next{};
         node* prev{};
         link (node* next, node* prev): next(next), prev(prev){}
      };
      struct node: link {
         value_type value{};
         node (node* next, node* prev, const value_type&);
      };
      node* anchor() { return static_cast<node*> (&anchor_); }
      link anchor_ {anchor(), anchor()};
   public:
      class iterator;
      listmap(){};
      listmap (const listmap&) = default;
      listmap& operator= (const listmap&) = default;
      ~listmap();
      iterator insert (const value_type&);
      iterator find (const key_type&);
      iterator erase (iterator position);
      iterator begin() { return anchor()->next; }
      iterator end() { return anchor(); }
      bool empty() const { return begin() == end(); }
};


template <typename Key, typename Value, class Less>
class listmap<Key,Value,Less>::iterator {
   private:
      friend class listmap<Key,Value>;
      listmap<Key,Value,Less>::node* where {nullptr};
      iterator (node* where): where(where){};
   public:
      iterator(){}
      value_type& operator*();
      value_type* operator->();
      iterator& operator++(); //++itor
      iterator& operator--(); //--itor
      void erase();
      bool operator== (const iterator&) const;
      bool operator!= (const iterator&) const;
};

template <typename Key, typename Value, class Less>
value_type& listmap<Key,Value,Less>::iterator<Key,Value,Less>::operator*()
{
      return where->value;
}

#include "listmap.tcc"
#endif

The problem is that value_type is a public member from the class listmap and it's not static, so I don't know how to complete the declaration of operator*(). I wouldn't like to fix the bug by changing the structure of the code. Ex: making

using value_type = xpair<const key_type, mapped_type>;

Global. I am just wondering if there is some other trick I can use to access value_type.

....edit: I have no idea how the inner class recognizes value_type

Answer 1

It's barely the same as for iterator, you just have to add typename keyword

typename listmap<Key,Value,Less>::value_type

static ness doesn't matter for a type.

The alias ¹ inside iterator

template <typename Key, typename Value, class Less>
class listmap<Key,Value,Less>::iterator {
    ...
    using value_type = typename listmap<Key,Value,Less>::value_type;

};

allows you to write the definition more succinctly using auto suffix type:

template <typename Key, typename Value, class Less>
auto listmap<Key,Value,Less>::iterator::operator*() -> value_type&
{
      return where->value;
}

Careful: inner iterator class is not template, only listmap is:

listmap<Key,Value,Less>::iterator<Key,Value,Less>::operator
//                               ~~~~~~~~~~~~~~~~ remove this

---

¹ Btw don't forget the others .