Sprout/sprout/iterator/traits.hpp

#ifndef SPROUT_ITERATOR_TRAITS_HPP
#define SPROUT_ITERATOR_TRAITS_HPP

#include <iterator>
#include <type_traits>
#include <sprout/config.hpp>
#include <sprout/type_traits/has_xxx.hpp>

namespace sprout {
	namespace detail {
		// has_iterator_category
		SPROUT_HAS_XXX_TYPE_DEF_LAZY(iterator_category);
	}	// namespace detail
	//
	// is_iterator
	//
	template<typename Iterator>
	struct is_iterator
		: sprout::detail::has_iterator_category<std::iterator_traits<Iterator> >
	{};

	//
	// is_input_iterator_category
	//
	template<typename Category>
	struct is_input_iterator_category
		: public std::is_convertible<Category, std::input_iterator_tag>
	{};
	//
	// is_output_iterator_category
	//
	template<typename Category>
	struct is_output_iterator_category
		: public std::is_convertible<Category, std::output_iterator_tag>
	{};
	//
	// is_forward_iterator_category
	//
	template<typename Category>
	struct is_forward_iterator_category
		: public std::is_convertible<Category, std::forward_iterator_tag>
	{};
	//
	// is_bidirectional_iterator_category
	//
	template<typename Category>
	struct is_bidirectional_iterator_category
		: public std::is_convertible<Category, std::bidirectional_iterator_tag>
	{};
	//
	// is_random_access_iterator_category
	//
	template<typename Category>
	struct is_random_access_iterator_category
		: public std::is_convertible<Category, std::random_access_iterator_tag>
	{};

	//
	// is_input_iterator
	//
	template<typename Iterator>
	struct is_input_iterator
		: public sprout::is_input_iterator_category<typename std::iterator_traits<Iterator>::iterator_category>
	{};
	//
	// is_output_iterator
	//
	template<typename Iterator>
	struct is_output_iterator
		: public sprout::is_output_iterator_category<typename std::iterator_traits<Iterator>::iterator_category>
	{};
	//
	// is_forward_iterator
	//
	template<typename Iterator>
	struct is_forward_iterator
		: public sprout::is_forward_iterator_category<typename std::iterator_traits<Iterator>::iterator_category>
	{};
	//
	// is_bidirectional_iterator
	//
	template<typename Iterator>
	struct is_bidirectional_iterator
		: public sprout::is_bidirectional_iterator_category<typename std::iterator_traits<Iterator>::iterator_category>
	{};
	//
	// is_random_access_iterator
	//
	template<typename Iterator>
	struct is_random_access_iterator
		: public sprout::is_random_access_iterator_category<typename std::iterator_traits<Iterator>::iterator_category>
	{};

	namespace detail {
		template<typename Category, bool IsRandomAccess, bool IsBidirectional, bool IsForward, bool IsSinglePassOrIncrementable>
		struct iterator_category_hierarchy_impl;
		template<typename Category, bool IsBidirectional, bool IsForward, bool IsSinglePassOrIncrementable>
		struct iterator_category_hierarchy_impl<Category, true, IsBidirectional, IsForward, IsSinglePassOrIncrementable>
			: public std::integral_constant<int, 4>
		{};
		template<typename Category, bool IsForward, bool IsSinglePassOrIncrementable>
		struct iterator_category_hierarchy_impl<Category, false, true, IsForward, IsSinglePassOrIncrementable>
			: public std::integral_constant<int, 3>
		{};
		template<typename Category, bool IsSinglePassOrIncrementable>
		struct iterator_category_hierarchy_impl<Category, false, false, true, IsSinglePassOrIncrementable>
			: public std::integral_constant<int, 2>
		{};
		template<typename Category>
		struct iterator_category_hierarchy_impl<Category, false, false, false, true>
			: public std::integral_constant<int, 1>
		{};

		template<typename Category>
		struct iterator_category_hierarchy
			: public sprout::detail::iterator_category_hierarchy_impl<
				Category,
				sprout::is_random_access_iterator_category<Category>::value,
				sprout::is_bidirectional_iterator_category<Category>::value,
				sprout::is_forward_iterator_category<Category>::value,
				sprout::is_input_iterator_category<Category>::value || sprout::is_output_iterator_category<Category>::value
			>
		{};

		template<typename Category1, typename Category2>
		struct iterator_category_less
			: public std::integral_constant<
				bool,
				(sprout::detail::iterator_category_hierarchy<Category1>::value < sprout::detail::iterator_category_hierarchy<Category2>::value)
			>
		{};
	}	// namespace detail
	//
	// min_iterator_category
	//
	template<typename Head, typename... Tail>
	struct min_iterator_category;
	template<typename Category>
	struct min_iterator_category<Category>
		: public std::common_type<Category>
	{};
	template<typename Category1, typename Category2>
	struct min_iterator_category<Category1, Category2>
		: public std::conditional<
			sprout::detail::iterator_category_less<Category1, Category2>::value,
			Category1, Category2
		>
	{};
	template<typename Head, typename... Tail>
	struct min_iterator_category
		: public sprout::min_iterator_category<
			Head,
			typename sprout::min_iterator_category<Tail...>::type
		>
	{};
}	// namespace sprout

#endif	// #ifndef SPROUT_ITERATOR_TRAITS_HPP