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/*!
@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>
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
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