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