/*! @file Defines `boost::hana::detail::first_unsatisfied_index`. @copyright Louis Dionne 2013-2017 Distributed under the Boost Software License, Version 1.0. (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt) */ #ifndef BOOST_HANA_DETAIL_FIRST_UNSATISFIED_INDEX_HPP #define BOOST_HANA_DETAIL_FIRST_UNSATISFIED_INDEX_HPP #include <boost/hana/config.hpp> #include <boost/hana/integral_constant.hpp> #include <boost/hana/value.hpp> #include <utility> namespace boost { namespace hana { namespace detail { template <bool, typename Pred, typename ...Xs> struct find_tail_size; template <typename Pred, typename X, typename ...Xs> struct find_tail_size<true, Pred, X, Xs...> { static constexpr int value = find_tail_size< static_cast<bool>(hana::value<decltype(std::declval<Pred>()(std::declval<X>()))>()), Pred, Xs... >::value; }; template <typename Pred> struct find_tail_size<true, Pred> { static constexpr int value = -1; }; template <typename Pred, typename ...Xs> struct find_tail_size<false, Pred, Xs...> { static constexpr int value = sizeof...(Xs); }; //! @ingroup group-details //! Returns the index of the first element which does not satisfy `Pred`, //! or `sizeof...(Xs)` if no such element exists. template <typename Pred> struct first_unsatisfied_index { template <typename ...Xs> constexpr auto operator()(Xs&& ...) const { return hana::size_c< sizeof...(Xs) - 1 - find_tail_size<true, Pred, Xs&&...>::value >; } }; } }} // end namespace boost::hana #endif // !BOOST_HANA_DETAIL_FIRST_UNSATISFIED_INDEX_HPP