Include remove_reference.hpp only when needed.

add forward reference assignment operator to function_output_iterator

appveyor.yml

@@ -22,19 +22,24 @@ environment:
       ADDRMD: 32,64
       APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015
     - TOOLSET: msvc-14.0
+      CXXSTD: 14,latest
       ADDRMD: 32,64
       APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015
     - TOOLSET: msvc-14.1
-      CXXSTD: 14,17
+      CXXSTD: 14,17,latest
       ADDRMD: 32,64
       APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
     - TOOLSET: msvc-14.2
       ADDRMD: 32,64
-      CXXSTD: 14,17
+      CXXSTD: 14,17,20,latest
       APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2019
+    - TOOLSET: msvc-14.3
+      ADDRMD: 32,64
+      CXXSTD: 14,17,20,latest
+      APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2022
     - TOOLSET: clang-win
       ADDRMD: 32,64
-      CXXSTD: 14,17
+      CXXSTD: 14,17,latest
       APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
     - TOOLSET: gcc
       CXXSTD: 03,11,14,1z

include/boost/iterator/function_output_iterator.hpp

@@ -12,13 +12,53 @@
 #define BOOST_ITERATOR_FUNCTION_OUTPUT_ITERATOR_HPP
 
 #include <iterator>
+#include <boost/config.hpp>
+#include <boost/core/enable_if.hpp>
+#include <boost/type_traits/is_same.hpp>
+#include <boost/type_traits/remove_cv.hpp>
+#ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
+#include <boost/type_traits/remove_reference.hpp>
+#endif
 
 namespace boost {
 namespace iterators {
 
   template <class UnaryFunction>
   class function_output_iterator {
+  private:
     typedef function_output_iterator self;
+
+    class output_proxy {
+    public:
+      explicit output_proxy(UnaryFunction& f) BOOST_NOEXCEPT : m_f(f) { }
+
+#ifdef BOOST_NO_CXX11_RVALUE_REFERENCES
+      template <class T>
+      typename boost::disable_if_c<
+        boost::is_same< typename boost::remove_cv< T >::type, output_proxy >::value,
+        output_proxy&
+      >::type operator=(const T& value) {
+        m_f(value);
+        return *this;
+      }
+#else
+      template <class T>
+      typename boost::disable_if_c<
+        boost::is_same< typename boost::remove_cv< typename boost::remove_reference< T >::type >::type, output_proxy >::value,
+        output_proxy&
+      >::type operator=(T&& value) {
+        m_f(static_cast< T&& >(value));
+        return *this;
+      }
+#endif
+
+      BOOST_DEFAULTED_FUNCTION(output_proxy(output_proxy const& that), BOOST_NOEXCEPT : m_f(that.m_f) {})
+      BOOST_DELETED_FUNCTION(output_proxy& operator=(output_proxy const&))
+
+    private:
+      UnaryFunction& m_f;
+    };
+
   public:
     typedef std::output_iterator_tag iterator_category;
     typedef void                value_type;
@@ -31,17 +71,10 @@ namespace iterators {
     explicit function_output_iterator(const UnaryFunction& f)
       : m_f(f) {}
 
-    struct output_proxy {
-      output_proxy(UnaryFunction& f) : m_f(f) { }
-      template <class T> output_proxy& operator=(const T& value) {
-        m_f(value);
-        return *this;
-      }
-      UnaryFunction& m_f;
-    };
     output_proxy operator*() { return output_proxy(m_f); }
     self& operator++() { return *this; }
     self& operator++(int) { return *this; }
+
   private:
     UnaryFunction m_f;
   };

test/Jamfile.v2

@@ -50,6 +50,8 @@ test-suite iterator
     [ run permutation_iterator_test.cpp : : : # <stlport-iostream>on
     ]
     [ run function_input_iterator_test.cpp ]
+    [ run function_output_iterator_test.cpp ]
+    [ compile-fail function_output_iterator_cf.cpp ]
 
     [ run generator_iterator_test.cpp ]
 

test/function_output_iterator_cf.cpp

@@ -0,0 +1,37 @@
+// Copyright 2022 (c) Andrey Semashev
+// Distributed under the Boost Software License Version 1.0.
+// (See accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt)
+
+#include <boost/iterator/function_output_iterator.hpp>
+
+namespace {
+
+struct sum_func
+{
+    typedef void result_type;
+
+    explicit sum_func(int& n) : m_n(n) {}
+    result_type operator() (int x) const
+    {
+        m_n += x;
+    }
+
+private:
+    int& m_n;
+};
+
+} // namespace
+
+int main()
+{
+    int n = 0;
+    boost::iterators::function_output_iterator< sum_func > it1 =
+        boost::iterators::make_function_output_iterator(sum_func(n));
+    boost::iterators::function_output_iterator< sum_func > it2 =
+        boost::iterators::make_function_output_iterator(sum_func(n));
+
+    *it1 = *it2;
+
+    return 0;
+}

test/function_output_iterator_test.cpp

@@ -0,0 +1,61 @@
+// Copyright 2022 (c) Andrey Semashev
+// Distributed under the Boost Software License Version 1.0.
+// (See accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt)
+
+#include <boost/config.hpp>
+
+#include <boost/core/lightweight_test.hpp>
+#include <boost/iterator/function_output_iterator.hpp>
+
+namespace {
+
+struct sum_func
+{
+    typedef void result_type;
+
+    explicit sum_func(int& n) : m_n(n) {}
+    result_type operator() (int x) const
+    {
+        m_n += x;
+    }
+
+private:
+    int& m_n;
+};
+
+} // namespace
+
+int main()
+{
+    {
+        int n = 0;
+        boost::iterators::function_output_iterator< sum_func > it =
+            boost::iterators::make_function_output_iterator(sum_func(n));
+
+        *it = 1;
+        ++it;
+        *it = 2;
+        ++it;
+        *it = 3;
+
+        BOOST_TEST_EQ(n, 6);
+    }
+
+#if !defined(BOOST_NO_CXX11_LAMBDAS) && !defined(BOOST_NO_CXX11_AUTO_DECLARATIONS)
+    {
+        int n = 0;
+        auto it = boost::iterators::make_function_output_iterator([&n](int x) { n -= x; });
+
+        *it = 1;
+        ++it;
+        *it = 2;
+        ++it;
+        *it = 3;
+
+        BOOST_TEST_EQ(n, -6);
+    }
+#endif
+
+    return boost::report_errors();
+}