Wed, 23 Mar 2016 14:58:22 GMT

Here's a simple fix, which works as long as the value type is DefaultConstructible:

--- boost/boost/iterator/iterator_facade.hpp
+++ boost/boost/iterator/iterator_facade.hpp
@@ -152,8 +152,9 @@
     template <class Iterator>
     class postfix_increment_proxy
     {
+     public:
         typedef typename iterator_value<Iterator>::type value_type;
-     public:
+        postfix_increment_proxy() {}
         explicit postfix_increment_proxy(Iterator const& x)
           : stored_value(*x)
         {}
@@ -178,8 +179,9 @@
     template <class Iterator>
     class writable_postfix_increment_proxy
     {
+     public:
         typedef typename iterator_value<Iterator>::type value_type;
-     public:
+        writable_postfix_increment_proxy() {}
         explicit writable_postfix_increment_proxy(Iterator const& x)
           : stored_value(*x)
           , stored_iterator(x)

To work around values which aren't DefaultConstructible, it might be necessary to wrap the stored_value in optional, but the above simple fix will work for majority of cases.

summary changed

Wed, 20 Apr 2016 15:21:25 GMT

summary postfix_increment_proxy is not DefaultConstructible and doesn't have a nested public value_type → Using iterator_facade with range-v3 fails to compile

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)));
}

Boost C++ Libraries: Ticket #12071: Using iterator_facade with range-v3 fails to compile

summary changed