text: /*!
  @file
  Defines `boost::hana::detail::first_unsatisfied_index`.
  
  @copyright Louis Dionne 2013-2016
  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>
  
  
  BOOST_HANA_NAMESPACE_BEGIN 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
              >;
          }
      };
  } BOOST_HANA_NAMESPACE_END
  
  #endif // !BOOST_HANA_DETAIL_FIRST_UNSATISFIED_INDEX_HPP
  