From 47ff2e6cb5c8479cf2b7875867590f0af1f99324 Mon Sep 17 00:00:00 2001
From: Kohei Takahashi <flast@flast.jp>
Date: Sat, 7 Jul 2018 07:18:56 +0900
Subject: [PATCH] find_if: Improved tag usage

The traversal tag is a bit complex than before.
---
 .../fusion/algorithm/query/detail/find_if.hpp | 25 ++++++-------------
 1 file changed, 8 insertions(+), 17 deletions(-)

diff --git a/include/boost/fusion/algorithm/query/detail/find_if.hpp b/include/boost/fusion/algorithm/query/detail/find_if.hpp
index 56c5296c..06a7af79 100644
--- a/include/boost/fusion/algorithm/query/detail/find_if.hpp
+++ b/include/boost/fusion/algorithm/query/detail/find_if.hpp
@@ -22,10 +22,9 @@
 #include <boost/fusion/sequence/intrinsic/begin.hpp>
 #include <boost/fusion/sequence/intrinsic/end.hpp>
 #include <boost/fusion/support/category_of.hpp>
+#include <boost/core/enable_if.hpp>
 
-namespace boost { namespace fusion { 
-    struct random_access_traversal_tag;
-namespace detail
+namespace boost { namespace fusion { namespace detail
 {
     template <typename Iterator, typename Pred>
     struct apply_filter
@@ -179,7 +178,7 @@ namespace detail
                 First
               , Last
               , Pred
-              , is_base_of<random_access_traversal_tag, typename traits::category_of<First>::type>::value
+              , traits::is_random_access<First>::value
             >::type
         type;
 
@@ -208,31 +207,23 @@ namespace detail
             return recursive_call(iter, found());
         }
 
-        template <typename Iterator, typename Tag>
+        template <typename Iterator>
         BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
-        static type
-        choose_call(Iterator const& iter, Tag)
+        static typename boost::disable_if<traits::is_random_access<Iterator>, type>::type
+        iter_call(Iterator const& iter)
         {
             return recursive_call(iter);
         }
 
         template <typename Iterator>
         BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
-        static type
-        choose_call(Iterator const& iter, random_access_traversal_tag)
+        static typename boost::enable_if<traits::is_random_access<Iterator>, type>::type
+        iter_call(Iterator const& iter)
         {
             typedef typename result_of::distance<Iterator, type>::type N;
             return fusion::advance<N>(iter);
         }
 
-        template <typename Iterator>
-        BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
-        static type
-        iter_call(Iterator const& iter)
-        {
-            return choose_call(iter, typename traits::category_of<Iterator>::type());
-        }
-
         template <typename Sequence>
         BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
         static type