From 465c3f273b59e4341a249d05bb9fc856f50722fe Mon Sep 17 00:00:00 2001
From: Kohei Takahashi <flast@flast.jp>
Date: Mon, 10 Nov 2014 14:38:42 +0900
Subject: [PATCH] result_of::{copy,move,swap} are now SFINAE-friendly

---
 doc/algorithm.qbk                                 |  6 ++++--
 doc/fusion.qbk                                    |  2 ++
 doc/sequence.qbk                                  | 13 +++++++++----
 include/boost/fusion/algorithm/auxiliary/copy.hpp | 12 +++++-------
 include/boost/fusion/algorithm/auxiliary/move.hpp | 12 +++++-------
 include/boost/fusion/sequence/intrinsic/swap.hpp  | 12 +++++++-----
 6 files changed, 32 insertions(+), 25 deletions(-)

diff --git a/doc/algorithm.qbk b/doc/algorithm.qbk
index dcb911fd..d902ebe4 100644
--- a/doc/algorithm.qbk
+++ b/doc/algorithm.qbk
@@ -164,7 +164,8 @@ A metafunction returning the result type of applying __copy__, which is always `
 [heading Expression Semantics]
     result_of::copy<Seq1, Seq2>::type
 
-[*Return type]: `void`
+[*Return type]: `void` iff both of `Seq1` and `Seq2` are sequence.
+Otherwise, none.
 
 [*Semantics]: Returns the return type of __copy__ for 2 sequences of types `Seq1` and `Seq2`.
 
@@ -199,7 +200,8 @@ A metafunction returning the result type of applying __move__, which is always `
 [heading Expression Semantics]
     result_of::move<Seq1, Seq2>::type
 
-[*Return type]: `void`
+[*Return type]: `void` iff both of `Seq1` and `Seq2` are sequence.
+Otherwise, none.
 
 [*Semantics]: Returns the return type of __move__ for 2 sequences of types `Seq1` and `Seq2`.
 
diff --git a/doc/fusion.qbk b/doc/fusion.qbk
index 7a943c14..f6c5f654 100644
--- a/doc/fusion.qbk
+++ b/doc/fusion.qbk
@@ -178,6 +178,8 @@
 [def __result_of_value_at__     [link fusion.sequence.intrinsic.metafunctions.value_at `result_of::value_at`]]
 [def __result_of_value_at_c__   [link fusion.sequence.intrinsic.metafunctions.value_at_c `result_of::value_at_c`]]
 [def __result_of_value_at_key__ [link fusion.sequence.intrinsic.metafunctions.value_at_key `result_of::value_at_key`]]
+[def __swap__                   [link fusion.sequence.intrinsic.functions.swap `swap`]]
+[def __result_of_swap__         [link fusion.sequence.intrinsic.metafunctions.swap `result_of::swap`]]
 
 [def __conversion__             [link fusion.container.conversion.functions Conversion]]
 [def __result_of_conversion__   [link fusion.container.conversion.metafunctions Conversion Metafunctions]]
diff --git a/doc/sequence.qbk b/doc/sequence.qbk
index 40558cb7..3948a2ce 100644
--- a/doc/sequence.qbk
+++ b/doc/sequence.qbk
@@ -854,7 +854,8 @@ Performs an element by element swap of the elements in 2 sequences.
 
 [heading Synopsis]
     template<typename Seq1, typename Seq2>
-    void swap(Seq1& seq1, Seq2& seq2);
+    typename __result_of_swap__<Seq1, Seq2>::type
+    swap(Seq1& seq1, Seq2& seq2);
 
 [heading Parameters]
 
@@ -873,7 +874,10 @@ Performs an element by element swap of the elements in 2 sequences.
 
 [*Semantics]: Calls `swap(a1, b1)` for corresponding elements in `seq1` and `seq2`.
 
-/sequence/intrinsic/swap.hpp>
+[heading Header]
+
+    #include <boost/fusion/sequence/intrinsic/swap.hpp>
+    #include <boost/fusion/include/swap.hpp>
 
 [heading Example]
     __vector__<int, std::string> v1(1, "hello"), v2(2, "world");
@@ -1415,9 +1419,10 @@ Returns the return type of swap.
 [heading Expression Semantics]
     result_of::swap<Seq1, Seq2>::type
 
-[*Return type]: `void`.
+[*Return type]: `void` iff both of `Seq1` and `Seq2` are sequence.
+Otherwise, none.
 
-[*Semantics]: Always returns `void`.
+[*Semantics]: Returns the return type of __swap__ for 2 sequences of types `Seq1` and `Seq2`.
 
 [heading Header]
 
diff --git a/include/boost/fusion/algorithm/auxiliary/copy.hpp b/include/boost/fusion/algorithm/auxiliary/copy.hpp
index dab1a410..683a5c87 100644
--- a/include/boost/fusion/algorithm/auxiliary/copy.hpp
+++ b/include/boost/fusion/algorithm/auxiliary/copy.hpp
@@ -64,17 +64,15 @@ namespace boost { namespace fusion
     {
         template <typename Seq1, typename Seq2>
         struct copy
-        {
-            typedef void type;
-        };
+            : enable_if<mpl::and_<
+                  traits::is_sequence<Seq1>,
+                  traits::is_sequence<Seq2>
+              > > {};
     }
 
     template <typename Seq1, typename Seq2>
     BOOST_FUSION_GPU_ENABLED
-    inline typename enable_if<mpl::and_<
-        traits::is_sequence<Seq1>,
-        traits::is_sequence<Seq2>
-    > >::type
+    inline typename result_of::copy<Seq1 const, Seq2>::type
     copy(Seq1 const& src, Seq2& dest)
     {
         BOOST_STATIC_ASSERT(
diff --git a/include/boost/fusion/algorithm/auxiliary/move.hpp b/include/boost/fusion/algorithm/auxiliary/move.hpp
index ea938111..76ff4692 100644
--- a/include/boost/fusion/algorithm/auxiliary/move.hpp
+++ b/include/boost/fusion/algorithm/auxiliary/move.hpp
@@ -64,17 +64,15 @@ namespace boost { namespace fusion
     {
         template <typename Seq1, typename Seq2>
         struct move
-        {
-            typedef void type;
-        };
+            : enable_if<mpl::and_<
+                  traits::is_sequence<Seq1>,
+                  traits::is_sequence<Seq2>
+              > > {};
     }
 
     template <typename Seq1, typename Seq2>
     BOOST_FUSION_GPU_ENABLED
-    inline typename enable_if<mpl::and_<
-        traits::is_sequence<Seq1>,
-        traits::is_sequence<Seq2>
-    > >::type
+    inline typename result_of::move<Seq1, Seq2>::type
     move(Seq1&& src, Seq2& dest)
     {
         BOOST_STATIC_ASSERT(
diff --git a/include/boost/fusion/sequence/intrinsic/swap.hpp b/include/boost/fusion/sequence/intrinsic/swap.hpp
index 5b00caac..8c49dc48 100644
--- a/include/boost/fusion/sequence/intrinsic/swap.hpp
+++ b/include/boost/fusion/sequence/intrinsic/swap.hpp
@@ -14,19 +14,21 @@
 #include <boost/fusion/support/is_sequence.hpp>
 #include <boost/fusion/view/zip_view.hpp>
 #include <boost/fusion/algorithm/iteration/for_each.hpp>
-#include <boost/utility/enable_if.hpp>
 #include <boost/fusion/sequence/intrinsic/front.hpp>
 #include <boost/fusion/sequence/intrinsic/back.hpp>
+#include <boost/core/enable_if.hpp>
 #include <boost/mpl/and.hpp>
 
 namespace boost { namespace fusion {
+
     namespace result_of
     {
         template<typename Seq1, typename Seq2>
         struct swap
-        {
-            typedef void type;
-        };
+            : enable_if<mpl::and_<
+                  traits::is_sequence<Seq1>,
+                  traits::is_sequence<Seq2>
+              > > {};
     }
 
     namespace detail
@@ -51,7 +53,7 @@ namespace boost { namespace fusion {
 
     template<typename Seq1, typename Seq2>
     BOOST_CXX14_CONSTEXPR BOOST_FUSION_GPU_ENABLED
-    inline typename enable_if<mpl::and_<traits::is_sequence<Seq1>, traits::is_sequence<Seq2> >, void>::type
+    inline typename result_of::swap<Seq1, Seq2>::type
     swap(Seq1& lhs, Seq2& rhs)
     {
         typedef vector<Seq1&, Seq2&> references;