diff --git a/sprout/assert.hpp b/sprout/assert.hpp
index 795d3b21..99b9d937 100644
--- a/sprout/assert.hpp
+++ b/sprout/assert.hpp
@@ -26,9 +26,7 @@
 #	include <sprout/preprocessor/cat.hpp>
 #	include <sprout/preprocessor/variadic/size.hpp>
 #endif
-#if !(defined(SPROUT_DISABLE_ASSERTS) || defined(NDEBUG))
-#	include <sprout/preprocessor/stringize.hpp>
-#endif
+#include <sprout/preprocessor/stringize.hpp>
 
 //
 // SPROUT_ASSERTION_FAILED_FORMAT
diff --git a/sprout/container/container_range_traits.hpp b/sprout/container/container_range_traits.hpp
index 0b6b3c67..c1bda2df 100644
--- a/sprout/container/container_range_traits.hpp
+++ b/sprout/container/container_range_traits.hpp
@@ -337,6 +337,150 @@ namespace sprout {
 			}
 		};
 
+		template<typename T>
+		struct has_mem_nth_test {
+		public:
+			template<
+				typename U = T,
+				typename = typename sprout::identity<decltype(std::declval<U>().nth(std::declval<typename sprout::container_traits<U>::size_type>()))>::type
+			>
+			static sprout::true_type test(int);
+			static sprout::false_type test(...);
+		};
+#if defined(_MSC_VER)
+		template<typename T, typename Base_ = typename sprout::identity<decltype(sprout::detail::has_mem_nth_test<T>::test(0))>::type>
+		struct has_mem_nth
+			: public Base_
+		{};
+#else
+		template<typename T>
+		struct has_mem_nth
+			: public sprout::identity<decltype(sprout::detail::has_mem_nth_test<T>::test(0))>::type
+		{};
+#endif
+
+		template<typename Container, typename = void>
+		struct container_range_traits_range_nth_impl;
+		template<typename Container>
+		struct container_range_traits_range_nth_impl<
+			Container,
+			typename std::enable_if<sprout::detail::has_mem_nth<Container>::value>::type
+		> {
+		public:
+			static SPROUT_CONSTEXPR typename sprout::container_traits<Container>::iterator
+			range_nth(Container& cont, typename sprout::container_traits<Container>::size_type i) {
+				return cont.nth(i);
+			}
+		};
+		template<typename Container>
+		struct container_range_traits_range_nth_impl<
+			Container,
+			typename std::enable_if<!sprout::detail::has_mem_nth<Container>::value>::type
+		> {
+		public:
+			static SPROUT_CONSTEXPR typename sprout::container_traits<Container>::iterator
+			range_nth(Container& cont, typename sprout::container_traits<Container>::size_type i) {
+				return sprout::next(sprout::begin(cont), i);
+			}
+		};
+
+		template<typename Container, typename = void>
+		struct container_range_traits_range_nth_const_impl;
+		template<typename Container>
+		struct container_range_traits_range_nth_const_impl<
+			Container,
+			typename std::enable_if<sprout::detail::has_mem_nth<Container const>::value>::type
+		> {
+		public:
+			static SPROUT_CONSTEXPR typename sprout::container_traits<Container const>::iterator
+			range_nth(Container const& cont, typename sprout::container_traits<Container const>::size_type i) {
+				return cont.nth(i);
+			}
+		};
+		template<typename Container>
+		struct container_range_traits_range_nth_const_impl<
+			Container,
+			typename std::enable_if<!sprout::detail::has_mem_nth<Container const>::value>::type
+		> {
+		public:
+			static SPROUT_CONSTEXPR typename sprout::container_traits<Container const>::iterator
+			range_nth(Container const& cont, typename sprout::container_traits<Container const>::size_type i) {
+				return sprout::next(sprout::begin(cont), i);
+			}
+		};
+
+		template<typename T>
+		struct has_mem_index_of_test {
+		public:
+			template<
+				typename U = T,
+				typename = typename sprout::identity<decltype(std::declval<U>().index_of(std::declval<typename sprout::container_traits<U>::iterator>()))>::type
+			>
+			static sprout::true_type test(int);
+			static sprout::false_type test(...);
+		};
+#if defined(_MSC_VER)
+		template<typename T, typename Base_ = typename sprout::identity<decltype(sprout::detail::has_mem_index_of_test<T>::test(0))>::type>
+		struct has_mem_index_of
+			: public Base_
+		{};
+#else
+		template<typename T>
+		struct has_mem_index_of
+			: public sprout::identity<decltype(sprout::detail::has_mem_index_of_test<T>::test(0))>::type
+		{};
+#endif
+
+		template<typename Container, typename = void>
+		struct container_range_traits_range_index_of_impl;
+		template<typename Container>
+		struct container_range_traits_range_index_of_impl<
+			Container,
+			typename std::enable_if<sprout::detail::has_mem_index_of<Container>::value>::type
+		> {
+		public:
+			static SPROUT_CONSTEXPR typename sprout::container_traits<Container>::size_type
+			range_index_of(Container& cont, typename sprout::container_traits<Container>::iterator p) {
+				return cont.index_of(p);
+			}
+		};
+		template<typename Container>
+		struct container_range_traits_range_index_of_impl<
+			Container,
+			typename std::enable_if<!sprout::detail::has_mem_index_of<Container>::value>::type
+		> {
+		public:
+			static SPROUT_CONSTEXPR typename sprout::container_traits<Container>::size_type
+			range_index_of(Container& cont, typename sprout::container_traits<Container>::iterator p) {
+				return sprout::distance(sprout::begin(cont), p);
+			}
+		};
+
+		template<typename Container, typename = void>
+		struct container_range_traits_range_index_of_const_impl;
+		template<typename Container>
+		struct container_range_traits_range_index_of_const_impl<
+			Container,
+			typename std::enable_if<sprout::detail::has_mem_index_of<Container const>::value>::type
+		> {
+		public:
+			static SPROUT_CONSTEXPR typename sprout::container_traits<Container const>::size_type
+			range_index_of(Container const& cont, typename sprout::container_traits<Container const>::iterator p) {
+				return cont.index_of(p);
+			}
+		};
+		template<typename Container>
+		struct container_range_traits_range_index_of_const_impl<
+			Container,
+			typename std::enable_if<!sprout::detail::has_mem_index_of<Container const>::value>::type
+		> {
+		public:
+			static SPROUT_CONSTEXPR typename sprout::container_traits<Container const>::size_type
+			range_index_of(Container const& cont, typename sprout::container_traits<Container const>::iterator p) {
+				return sprout::distance(sprout::begin(cont), p);
+			}
+		};
+
 		//
 		// container_range_traits_default
 		//
@@ -350,6 +494,10 @@ namespace sprout {
 			, public sprout::detail::container_range_traits_range_back_const_impl<Container>
 			, public sprout::detail::container_range_traits_range_at_impl<Container>
 			, public sprout::detail::container_range_traits_range_at_const_impl<Container>
+			, public sprout::detail::container_range_traits_range_nth_impl<Container>
+			, public sprout::detail::container_range_traits_range_nth_const_impl<Container>
+			, public sprout::detail::container_range_traits_range_index_of_impl<Container>
+			, public sprout::detail::container_range_traits_range_index_of_const_impl<Container>
 		{
 			using sprout::detail::container_range_traits_range_front_impl<Container>::range_front;
 			using sprout::detail::container_range_traits_range_front_const_impl<Container>::range_front;
@@ -357,6 +505,10 @@ namespace sprout {
 			using sprout::detail::container_range_traits_range_back_const_impl<Container>::range_back;
 			using sprout::detail::container_range_traits_range_at_impl<Container>::range_at;
 			using sprout::detail::container_range_traits_range_at_const_impl<Container>::range_at;
+			using sprout::detail::container_range_traits_range_nth_impl<Container>::range_nth;
+			using sprout::detail::container_range_traits_range_nth_const_impl<Container>::range_nth;
+			using sprout::detail::container_range_traits_range_index_of_impl<Container>::range_index_of;
+			using sprout::detail::container_range_traits_range_index_of_const_impl<Container>::range_index_of;
 		public:
 			// iterators:
 			static SPROUT_CONSTEXPR typename sprout::container_traits<Container>::iterator
@@ -422,6 +574,14 @@ namespace sprout {
 			range_at(Container const& cont, typename sprout::container_traits<Container const>::size_type i) {
 				return sprout::container_range_traits<Container>::range_at(cont, i);
 			}
+			static SPROUT_CONSTEXPR typename sprout::container_traits<Container const>::iterator
+			range_nth(Container const& cont, typename sprout::container_traits<Container const>::size_type i) {
+				return sprout::container_range_traits<Container>::range_nth(cont, i);
+			}
+			static SPROUT_CONSTEXPR typename sprout::container_traits<Container const>::size_type
+			range_index_of(Container const& cont, typename sprout::container_traits<Container const>::iterator p) {
+				return sprout::container_range_traits<Container>::range_index_of(cont, p);
+			}
 			// data access:
 			static SPROUT_CONSTEXPR typename sprout::container_traits<Container const>::pointer
 			range_data(Container const& cont) {
@@ -500,14 +660,36 @@ namespace sprout {
 		range_at(T const (& arr)[N], typename sprout::container_traits<T const[N]>::size_type i) {
 			return arr[i];
 		}
+		static SPROUT_CONSTEXPR typename sprout::container_traits<T[N]>::iterator
+		range_nth(T (& arr)[N], typename sprout::container_traits<T[N]>::size_type i) {
+			typedef typename sprout::container_traits<T[N]>::iterator type;
+			return type(arr) + i;
+		}
+		static SPROUT_CONSTEXPR typename sprout::container_traits<T const[N]>::iterator
+		range_nth(T const (& arr)[N], typename sprout::container_traits<T const[N]>::size_type i) {
+			typedef typename sprout::container_traits<T const[N]>::iterator type;
+			return type(arr) + i;
+		}
+		static SPROUT_CONSTEXPR typename sprout::container_traits<T[N]>::size_type
+		range_index_of(T (& arr)[N], typename sprout::container_traits<T[N]>::iterator p) {
+			typedef typename sprout::container_traits<T[N]>::iterator type;
+			return sprout::distance(type(arr), p);
+		}
+		static SPROUT_CONSTEXPR typename sprout::container_traits<T const[N]>::size_type
+		range_index_of(T const (& arr)[N], typename sprout::container_traits<T const[N]>::iterator p) {
+			typedef typename sprout::container_traits<T const[N]>::iterator type;
+			return sprout::distance(type(arr), p);
+		}
 		// data access:
 		static SPROUT_CONSTEXPR typename sprout::container_traits<T[N]>::pointer
 		range_data(T (& arr)[N]) {
-			return &arr[0];
+			typedef typename sprout::container_traits<T[N]>::pointer type;
+			return type(arr);
 		}
 		static SPROUT_CONSTEXPR typename sprout::container_traits<T const[N]>::pointer
 		range_data(T const (& arr)[N]) {
-			return &arr[0];
+			typedef typename sprout::container_traits<T const[N]>::pointer type;
+			return type(arr);
 		}
 	};
 	template<typename T, std::size_t N>
@@ -544,6 +726,14 @@ namespace sprout {
 		range_at(T const (& arr)[N], typename sprout::container_traits<T const[N]>::size_type i) {
 			return sprout::container_range_traits<T[N]>::range_at(arr, i);
 		}
+		static SPROUT_CONSTEXPR typename sprout::container_traits<T const[N]>::iterator
+		range_nth(T const (& arr)[N], typename sprout::container_traits<T const[N]>::size_type i) {
+			return sprout::container_range_traits<T[N]>::range_nth(arr, i);
+		}
+		static SPROUT_CONSTEXPR typename sprout::container_traits<T const[N]>::size_type
+		range_index_of(T const (& arr)[N], typename sprout::container_traits<T const[N]>::iterator p) {
+			return sprout::container_range_traits<T[N]>::range_index_of(arr, p);
+		}
 		// data access:
 		static SPROUT_CONSTEXPR typename sprout::container_traits<T const[N]>::pointer
 		range_data(T const (& arr)[N]) {
diff --git a/sprout/container/index_of.hpp b/sprout/container/index_of.hpp
new file mode 100644
index 00000000..4de98676
--- /dev/null
+++ b/sprout/container/index_of.hpp
@@ -0,0 +1,87 @@
+/*=============================================================================
+  Copyright (c) 2011-2015 Bolero MURAKAMI
+  https://github.com/bolero-MURAKAMI/Sprout
+
+  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)
+=============================================================================*/
+#ifndef SPROUT_CONTAINER_INDEX_OF_HPP
+#define SPROUT_CONTAINER_INDEX_OF_HPP
+
+#include <sprout/config.hpp>
+#include <sprout/workaround/std/cstddef.hpp>
+#include <sprout/container/traits_fwd.hpp>
+#include <sprout/container/container_traits.hpp>
+#include <sprout/adl/not_found.hpp>
+
+namespace sprout_adl {
+	sprout::not_found_via_adl range_index_of(...);
+}	// namespace sprout_adl
+
+namespace sprout {
+	namespace container_detail {
+		template<typename Container>
+		inline SPROUT_CONSTEXPR typename sprout::container_traits<Container>::size_type
+		range_index_of(Container& cont, typename sprout::container_traits<Container>::iterator p) {
+			return sprout::container_range_traits<Container>::range_index_of(cont, p);
+		}
+		template<typename Container>
+		inline SPROUT_CONSTEXPR typename sprout::container_traits<Container const>::size_type
+		range_index_of(Container const& cont, typename sprout::container_traits<Container const>::iterator p) {
+			return sprout::container_range_traits<Container>::range_index_of(cont, p);
+		}
+	}	// namespace container_detail
+
+	//
+	// index_of
+	//
+	//	effect:
+	//		ADL callable range_index_of(cont, p) -> range_index_of(cont, p)
+	//		otherwise -> sprout::container_range_traits<Container>::range_index_of(cont, p)
+	//		[default]
+	//			callable cont.index_of(p) -> cont.index_of(p)
+	//			otherwise -> *next(begin(cont), p)
+	//
+	template<typename Container>
+	inline SPROUT_CONSTEXPR typename sprout::container_traits<Container>::size_type
+	index_of(Container& cont, typename sprout::container_traits<Container>::iterator p) {
+		using sprout::container_detail::range_index_of;
+		using sprout_adl::range_index_of;
+		return range_index_of(cont, p);
+	}
+	template<typename Container>
+	inline SPROUT_CONSTEXPR typename sprout::container_traits<Container const>::size_type
+	index_of(Container const& cont, typename sprout::container_traits<Container const>::iterator p) {
+		using sprout::container_detail::range_index_of;
+		using sprout_adl::range_index_of;
+		return range_index_of(cont, p);
+	}
+	template<typename T, std::size_t N>
+	inline SPROUT_CONSTEXPR typename sprout::container_traits<T[N]>::size_type
+	index_of(T (& arr)[N], typename sprout::container_traits<T[N]>::iterator p) {
+		return sprout::container_detail::range_index_of(arr, p);
+	}
+	template<typename T, std::size_t N>
+	inline SPROUT_CONSTEXPR typename sprout::container_traits<T const[N]>::size_type
+	index_of(T const (& arr)[N], typename sprout::container_traits<T const[N]>::iterator p) {
+		return sprout::container_detail::range_index_of(arr, p);
+	}
+
+	//
+	// cindex_of
+	//
+	template<typename Container>
+	inline SPROUT_CONSTEXPR typename sprout::container_traits<Container const>::size_type
+	cindex_of(Container const& cont, typename sprout::container_traits<Container const>::iterator p) {
+		return sprout::index_of(cont, p);
+	}
+	template<typename T, std::size_t N>
+	inline SPROUT_CONSTEXPR typename sprout::container_traits<T const[N]>::size_type
+	cindex_of(T const (& arr)[N], typename sprout::container_traits<T const[N]>::iterator p) {
+		return sprout::index_of(arr, p);
+	}
+}	// namespace sprout
+
+#include <sprout/container/container_range_traits.hpp>
+
+#endif	// #ifndef SPROUT_CONTAINER_INDEX_OF_HPP
diff --git a/sprout/container/nth.hpp b/sprout/container/nth.hpp
new file mode 100644
index 00000000..e4ff234f
--- /dev/null
+++ b/sprout/container/nth.hpp
@@ -0,0 +1,87 @@
+/*=============================================================================
+  Copyright (c) 2011-2015 Bolero MURAKAMI
+  https://github.com/bolero-MURAKAMI/Sprout
+
+  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)
+=============================================================================*/
+#ifndef SPROUT_CONTAINER_NTH_HPP
+#define SPROUT_CONTAINER_NTH_HPP
+
+#include <sprout/config.hpp>
+#include <sprout/workaround/std/cstddef.hpp>
+#include <sprout/container/traits_fwd.hpp>
+#include <sprout/container/container_traits.hpp>
+#include <sprout/adl/not_found.hpp>
+
+namespace sprout_adl {
+	sprout::not_found_via_adl range_nth(...);
+}	// namespace sprout_adl
+
+namespace sprout {
+	namespace container_detail {
+		template<typename Container>
+		inline SPROUT_CONSTEXPR typename sprout::container_traits<Container>::iterator
+		range_nth(Container& cont, typename sprout::container_traits<Container>::size_type i) {
+			return sprout::container_range_traits<Container>::range_nth(cont, i);
+		}
+		template<typename Container>
+		inline SPROUT_CONSTEXPR typename sprout::container_traits<Container const>::iterator
+		range_nth(Container const& cont, typename sprout::container_traits<Container const>::size_type i) {
+			return sprout::container_range_traits<Container>::range_nth(cont, i);
+		}
+	}	// namespace container_detail
+
+	//
+	// nth
+	//
+	//	effect:
+	//		ADL callable range_nth(cont, i) -> range_nth(cont, i)
+	//		otherwise -> sprout::container_range_traits<Container>::range_nth(cont, i)
+	//		[default]
+	//			callable cont.nth(i) -> cont.nth(i)
+	//			otherwise -> *next(begin(cont), i)
+	//
+	template<typename Container>
+	inline SPROUT_CONSTEXPR typename sprout::container_traits<Container>::iterator
+	nth(Container& cont, typename sprout::container_traits<Container>::size_type i) {
+		using sprout::container_detail::range_nth;
+		using sprout_adl::range_nth;
+		return range_nth(cont, i);
+	}
+	template<typename Container>
+	inline SPROUT_CONSTEXPR typename sprout::container_traits<Container const>::iterator
+	nth(Container const& cont, typename sprout::container_traits<Container const>::size_type i) {
+		using sprout::container_detail::range_nth;
+		using sprout_adl::range_nth;
+		return range_nth(cont, i);
+	}
+	template<typename T, std::size_t N>
+	inline SPROUT_CONSTEXPR typename sprout::container_traits<T[N]>::iterator
+	nth(T (& arr)[N], typename sprout::container_traits<T[N]>::size_type i) {
+		return sprout::container_detail::range_nth(arr, i);
+	}
+	template<typename T, std::size_t N>
+	inline SPROUT_CONSTEXPR typename sprout::container_traits<T const[N]>::iterator
+	nth(T const (& arr)[N], typename sprout::container_traits<T const[N]>::size_type i) {
+		return sprout::container_detail::range_nth(arr, i);
+	}
+
+	//
+	// cnth
+	//
+	template<typename Container>
+	inline SPROUT_CONSTEXPR typename sprout::container_traits<Container const>::iterator
+	cnth(Container const& cont, typename sprout::container_traits<Container const>::size_type i) {
+		return sprout::nth(cont, i);
+	}
+	template<typename T, std::size_t N>
+	inline SPROUT_CONSTEXPR typename sprout::container_traits<T const[N]>::iterator
+	cnth(T const (& arr)[N], typename sprout::container_traits<T const[N]>::size_type i) {
+		return sprout::nth(arr, i);
+	}
+}	// namespace sprout
+
+#include <sprout/container/container_range_traits.hpp>
+
+#endif	// #ifndef SPROUT_CONTAINER_NTH_HPP
diff --git a/sprout/container/range_functions.hpp b/sprout/container/range_functions.hpp
index 2dbd0f44..ee95f2fe 100644
--- a/sprout/container/range_functions.hpp
+++ b/sprout/container/range_functions.hpp
@@ -17,6 +17,8 @@
 #include <sprout/container/front.hpp>
 #include <sprout/container/back.hpp>
 #include <sprout/container/at.hpp>
+#include <sprout/container/nth.hpp>
+#include <sprout/container/index_of.hpp>
 #include <sprout/container/data.hpp>
 
 #endif	// #ifndef SPROUT_CONTAINER_RANGE_FUNCTIONS_HPP
diff --git a/sprout/container/range_functions_fwd.hpp b/sprout/container/range_functions_fwd.hpp
index 37444477..3da3f93e 100644
--- a/sprout/container/range_functions_fwd.hpp
+++ b/sprout/container/range_functions_fwd.hpp
@@ -76,6 +76,26 @@ namespace sprout {
 	SPROUT_CONSTEXPR typename sprout::container_traits<Container const>::reference
 	at(Container const& cont, typename sprout::container_traits<Container const>::size_type i);
 
+	//
+	// nth
+	//
+	template<typename Container>
+	SPROUT_CONSTEXPR typename sprout::container_traits<Container>::iterator
+	nth(Container& cont, typename sprout::container_traits<Container>::size_type i);
+	template<typename Container>
+	SPROUT_CONSTEXPR typename sprout::container_traits<Container const>::iterator
+	nth(Container const& cont, typename sprout::container_traits<Container const>::size_type i);
+
+	//
+	// index_of
+	//
+	template<typename Container>
+	SPROUT_CONSTEXPR typename sprout::container_traits<Container>::size_type
+	index_of(Container& cont, typename sprout::container_traits<Container>::iterator p);
+	template<typename Container>
+	SPROUT_CONSTEXPR typename sprout::container_traits<Container const>::size_type
+	index_of(Container const& cont, typename sprout::container_traits<Container const>::iterator p);
+
 	//
 	// data
 	//
diff --git a/testspr/assert.hpp b/testspr/assert.hpp
index 11a12ac2..57f6d38e 100644
--- a/testspr/assert.hpp
+++ b/testspr/assert.hpp
@@ -54,7 +54,7 @@ namespace testspr {
 #define TESTSPR_STATIC_ASSERT(expr) \
 	static_assert(expr, #expr)
 #define TESTSPR_ASSERT(expr) \
-	((void)sprout::detail::assertion_check((expr), SPROUT_ASSERTION_FAILED_FORMAT(expr, __FILE__, __LINE__)))
+	SPROUT_ASSERT(expr)
 //
 // TESTSPR_BOTH_ASSERT
 //