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/* Copyright (C) 2016 Murray Cumming
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/
*/
#ifndef SIGC_TUPLE_UTILS_TUPLE_END_H
#define SIGC_TUPLE_UTILS_TUPLE_END_H
#include <sigc++/tuple-utils/tuple_cdr.h>
namespace sigc {
namespace internal {
namespace detail {
template <typename T, std::size_t remove_from_start>
struct tuple_end_impl {
constexpr
static
decltype(auto) // typename tuple_type_end<T, size - remove_from_start>::type
tuple_end(T&& t) {
static_assert(remove_from_start > 0, "remove_from_start must be more than zero.");
using cdr = typename tuple_type_cdr<std::decay_t<T>>::type;
return tuple_end_impl<cdr, remove_from_start - 1>::tuple_end(
tuple_cdr(std::forward<T>(t)));
}
};
template <typename T>
struct tuple_end_impl<T, 1> {
constexpr
static
decltype(auto)
tuple_end(T&& t) {
return tuple_cdr(std::forward<T>(t));
}
};
template <typename T>
struct tuple_end_impl<T, 0> {
constexpr
static
decltype(auto)
tuple_end(T&& t) {
return std::forward<T>(t);
}
};
} // detail namespace
/**
* Get the tuple with the last @a len items of the original.
*/
template <std::size_t len, typename T>
constexpr
decltype(auto) // typename tuple_type_end<T, len>::type
tuple_end(T&& t) {
//We use std::decay_t<> because tuple_size is not defined for references.
constexpr auto size = std::tuple_size<std::decay_t<T>>::value;
static_assert(len <= size, "The tuple size must be less than or equal to the length.");
constexpr auto size_start = size - len;
return detail::tuple_end_impl<T, size_start>::tuple_end(std::forward<T>(t));
}
} // namespace internal
} // namespace sigc
#endif //SIGC_TUPLE_UTILS_TUPLE_END_H
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