From a52257117e0e8df4b2ad2303f0547f5db962b512 Mon Sep 17 00:00:00 2001
From: bolero-MURAKAMI <bolero.murakami@gmail.com>
Date: Thu, 6 Oct 2011 15:08:59 +0900
Subject: [PATCH] =?UTF-8?q?next,=20prev=20=E4=BF=AE=E6=AD=A3?=
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---
 sprout/iterator/next.hpp |  6 ++++--
 sprout/iterator/prev.hpp | 16 ++++++++++------
 2 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/sprout/iterator/next.hpp b/sprout/iterator/next.hpp
index 54843544..a031f9b9 100644
--- a/sprout/iterator/next.hpp
+++ b/sprout/iterator/next.hpp
@@ -57,9 +57,10 @@ namespace sprout {
 	//
 	template<typename Iterator>
 	SPROUT_CONSTEXPR typename std::decay<Iterator>::type next(Iterator&& it) {
+		typedef typename std::iterator_traits<typename std::decay<Iterator>::type>::iterator_category* category;
 		return sprout::detail::next_impl(
 			sprout::forward<Iterator>(it),
-			static_cast<typename std::iterator_traits<typename std::decay<Iterator>::type>::iterator_category*>(nullptr)
+			category()
 			);
 	}
 	template<typename Iterator>
@@ -68,10 +69,11 @@ namespace sprout {
 		typename std::iterator_traits<typename std::decay<Iterator>::type>::difference_type n
 		)
 	{
+		typedef typename std::iterator_traits<typename std::decay<Iterator>::type>::iterator_category* category;
 		return sprout::detail::next_impl(
 			sprout::forward<Iterator>(it),
 			n,
-			static_cast<typename std::iterator_traits<typename std::decay<Iterator>::type>::iterator_category*>(nullptr)
+			category()
 			);
 	}
 }	// namespace sprout
diff --git a/sprout/iterator/prev.hpp b/sprout/iterator/prev.hpp
index 195edd4b..1eb9c099 100644
--- a/sprout/iterator/prev.hpp
+++ b/sprout/iterator/prev.hpp
@@ -20,12 +20,13 @@ namespace sprout {
 			return sprout::forward<Iterator>(it) - 1;
 		}
 		template<typename Iterator>
-		Iterator prev_impl(
+		SPROUT_CONSTEXPR typename std::decay<Iterator>::type prev_impl(
 			Iterator&& it,
 			void*
 			)
 		{
-			return std::prev(sprout::forward<Iterator>(it));
+			using std::prev;
+			return prev(sprout::forward<Iterator>(it));
 		}
 
 		template<typename Iterator>
@@ -41,13 +42,14 @@ namespace sprout {
 			return sprout::forward<Iterator>(it) - n;
 		}
 		template<typename Iterator>
-		Iterator prev_impl(
+		SPROUT_CONSTEXPR typename std::decay<Iterator>::type prev_impl(
 			Iterator it,
 			typename std::iterator_traits<typename std::decay<Iterator>::type>::difference_type n,
 			void*
 			)
 		{
-			return std::prev(sprout::forward<Iterator>(it), n);
+			using std::prev;
+			return prev(sprout::forward<Iterator>(it), n);
 		}
 	}	// namespace detail
 	//
@@ -55,9 +57,10 @@ namespace sprout {
 	//
 	template<typename Iterator>
 	SPROUT_CONSTEXPR typename std::decay<Iterator>::type prev(Iterator&& it) {
+		typedef typename std::iterator_traits<typename std::decay<Iterator>::type>::iterator_category* category;
 		return sprout::detail::prev_impl(
 			sprout::forward<Iterator>(it),
-			static_cast<typename std::iterator_traits<typename std::decay<Iterator>::type>::iterator_category*>(nullptr)
+			category()
 			);
 	}
 	template<typename Iterator>
@@ -66,10 +69,11 @@ namespace sprout {
 		typename std::iterator_traits<typename std::decay<Iterator>::type>::difference_type n
 		)
 	{
+		typedef typename std::iterator_traits<typename std::decay<Iterator>::type>::iterator_category* category;
 		return sprout::detail::prev_impl(
 			sprout::forward<Iterator>(it),
 			n,
-			static_cast<typename std::iterator_traits<typename std::decay<Iterator>::type>::iterator_category*>(nullptr)
+			category()
 			);
 	}
 }	// namespace sprout