#ifndef SPROUT_ITERATOR_PREV_HPP #define SPROUT_ITERATOR_PREV_HPP #include #include #include #include #include #include namespace sprout_adl { sprout::not_found_via_adl iterator_prev(...); } // namespace sprout_adl namespace sprout { namespace iterator_detail { template inline SPROUT_CONSTEXPR typename std::enable_if< std::is_literal_type::value, RandomAccessIterator >::type prev_impl(RandomAccessIterator const& it, std::random_access_iterator_tag*) { return it - 1; } template inline SPROUT_CONSTEXPR BidirectionalIterator prev_impl(BidirectionalIterator const& it, std::bidirectional_iterator_tag*) { return std::prev(it); } template inline SPROUT_CONSTEXPR typename std::enable_if< std::is_literal_type::value, RandomAccessIterator >::type prev_impl( RandomAccessIterator const& it, typename std::iterator_traits::difference_type n, std::random_access_iterator_tag* ) { return it - n; } template inline SPROUT_CONSTEXPR BidirectionalIterator prev_impl_1_neg(BidirectionalIterator const& it, typename std::iterator_traits::difference_type n) { return n == -1 ? sprout::next(it) : sprout::iterator_detail::prev_impl_1_neg( sprout::iterator_detail::prev_impl_1_neg(it, n / 2), n - (n / 2) ) ; } template inline SPROUT_CONSTEXPR BidirectionalIterator prev_impl_1(BidirectionalIterator const& it, typename std::iterator_traits::difference_type n) { return n == 1 ? sprout::prev(it) : sprout::iterator_detail::prev_impl_1( sprout::iterator_detail::prev_impl_1(it, n / 2), n - (n / 2) ) ; } template inline SPROUT_CONSTEXPR typename std::enable_if< std::is_literal_type::value, BidirectionalIterator >::type prev_impl( BidirectionalIterator const& it, typename std::iterator_traits::difference_type n, std::bidirectional_iterator_tag* ) { return n == 0 ? it : n > 0 ? sprout::iterator_detail::prev_impl_1(it, n) : sprout::iterator_detail::prev_impl_1_neg(it, n) ; } template inline SPROUT_CONSTEXPR typename std::enable_if< !std::is_literal_type::value, BidirectionalIterator >::type prev_impl( BidirectionalIterator const& it, typename std::iterator_traits::difference_type n, std::bidirectional_iterator_tag* ) { return std::prev(it, n); } template inline SPROUT_CONSTEXPR BidirectionalIterator iterator_prev(BidirectionalIterator const& it) { typedef typename std::iterator_traits::iterator_category* category; return sprout::iterator_detail::prev_impl(it, category()); } template inline SPROUT_CONSTEXPR BidirectionalIterator iterator_prev(BidirectionalIterator const& it, typename std::iterator_traits::difference_type n) { typedef typename std::iterator_traits::iterator_category* category; return sprout::iterator_detail::prev_impl(it, n, category()); } } // namespace iterator_detail } // namespace sprout namespace sprout_iterator_detail { template inline SPROUT_CONSTEXPR BidirectionalIterator prev(BidirectionalIterator const& it) { using sprout::iterator_detail::iterator_prev; using sprout_adl::iterator_prev; return iterator_prev(it); } template inline SPROUT_CONSTEXPR BidirectionalIterator prev(BidirectionalIterator const& it, typename std::iterator_traits::difference_type n) { using sprout::iterator_detail::iterator_prev; using sprout_adl::iterator_prev; return iterator_prev(it, n); } } // namespace sprout_iterator_detail namespace sprout { // // prev // // effect: // ADL callable iterator_prev(it) -> iterator_prev(it) // it is RandomAccessIterator && LiteralType -> it - 1 // otherwise -> std::prev(it) // template inline SPROUT_CONSTEXPR BidirectionalIterator prev(BidirectionalIterator const& it) { return sprout_iterator_detail::prev(it); } // // effect: // ADL callable iterator_prev(it, n) -> iterator_prev(it, n) // it is RandomAccessIterator && LiteralType -> it - n // it is LiteralType -> sprout::prev(it)... || sprout::next(it)... // otherwise -> std::prev(it, n) // template inline SPROUT_CONSTEXPR BidirectionalIterator prev(BidirectionalIterator const& it, typename std::iterator_traits::difference_type n) { return sprout_iterator_detail::prev(it, n); } } // namespace sprout #endif // #ifndef SPROUT_ITERATOR_PREV_HPP