Re: [Boost-bugs] [Boost C++ Libraries] #12071: Using iterator_facade with range-v3 fails to compile (was: postfix_increment_proxy is not DefaultConstructible and doesn't have a nested public value_type)

Subject: Re: [Boost-bugs] [Boost C++ Libraries] #12071: Using iterator_facade with range-v3 fails to compile (was: postfix_increment_proxy is not DefaultConstructible and doesn't have a nested public value_type)
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2016-04-20 15:21:25

#12071: Using iterator_facade with range-v3 fails to compile
----------------------------------------------+----------------------------
  Reporter:  Krzysztof Czaiński <1czajnik@…>  |      Owner:
      Type:  Bugs                             |  jeffrey.hellrung
 Milestone:  To Be Determined                 |     Status:  new
   Version:  Boost 1.61.0                     |  Component:  iterator
Resolution:                                   |   Severity:  Problem
                                              |   Keywords:  range-v3
----------------------------------------------+----------------------------

Comment (by Krzysztof Czaiński <1czajnik@…>):

 Maybe a high-level example will be helpful:

 {{{
 #include <iostream>

 #include "third_party/boost/allowed/iterator/iterator_facade.hpp"
 #include "third_party/range_v3/include/range/v3/algorithm/copy.hpp"
 #include "third_party/range_v3/include/range/v3/iterator_range.hpp"
 #include "third_party/range_v3/include/range/v3/utility/iterator.hpp"

 template <class V, class Category>
 class TestIter
     : public boost::iterator_facade<TestIter<V, Category>, V, Category, V>
 {
  public:
   using typename boost::iterator_facade<TestIter<V, Category>, V,
 Category,
                                         V>::difference_type;

   TestIter() : v_() {}

   explicit TestIter(V v) : v_(v) {}

  private:
   friend class boost::iterator_core_access;

   V dereference() const { return v_; }
   bool equal(const TestIter& other) const { return v_ == other.v_; }
   void increment() { ++v_; }
   void decrement() { --v_; }
   void advance(difference_type n) { v_ += n; }
   difference_type distance_to(const TestIter& other) const {
     return other.v_ - v_;
   }

   V v_;
 };

 using InIter = TestIter<int, std::input_iterator_tag>;

 template <class R>
 void print(R&& r) {
   ranges::copy(std::forward<R>(r), ranges::ostream_iterator<>(std::cout,
 ", "));
   std::cout << "\n";
 }

 int main() {
   print(ranges::make_iterator_range(InIter(1), InIter(10)));
 }
 }}}

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/12071#comment:2>
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