#ifndef BOOST_METAPARSE_V1_CPP11_IMPL_NTH_OF_C_HPP #define BOOST_METAPARSE_V1_CPP11_IMPL_NTH_OF_C_HPP // Copyright Abel Sinkovics (abel@sinkovics.hu) 2017. // 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) #include <boost/metaparse/v1/cpp11/impl/nth_of_c_skip_remaining.hpp> #include <boost/metaparse/v1/is_error.hpp> #include <boost/metaparse/v1/get_remaining.hpp> #include <boost/metaparse/v1/get_position.hpp> #include <boost/metaparse/v1/get_result.hpp> #include <type_traits> namespace boost { namespace metaparse { namespace v1 { namespace impl { template <int N, class S, class Pos, class... Ps> struct nth_of_c; template <int N, class S, class Pos, class P, class... Ps> struct nth_of_c<N, S, Pos, P, Ps...> { private: template <class NextResult> struct apply_unchecked : nth_of_c< N - 1, typename get_remaining<NextResult>::type, typename get_position<NextResult>::type, Ps... > {}; public: typedef typename std::conditional< is_error<typename P::template apply<S, Pos>>::type::value, typename P::template apply<S, Pos>, apply_unchecked<typename P::template apply<S, Pos>> >::type::type type; }; template <class P, class S, class Pos, class... Ps> struct nth_of_c<0, S, Pos, P, Ps...> { private: template <class NextResult> struct apply_unchecked : nth_of_c_skip_remaining< typename get_result<NextResult>::type, typename get_remaining<NextResult>::type, typename get_position<NextResult>::type, Ps... > {}; public: typedef typename std::conditional< is_error<typename P::template apply<S, Pos>>::type::value, typename P::template apply<S, Pos>, apply_unchecked<typename P::template apply<S, Pos>> >::type::type type; }; } } } } #endif