Current File : //backups/router/usr/local/include/boost/hana/fwd/take_back.hpp
/*!
@file
Forward declares `boost::hana::take_back`.
Copyright Louis Dionne 2013-2022
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_FWD_TAKE_BACK_HPP
#define BOOST_HANA_FWD_TAKE_BACK_HPP
#include <boost/hana/config.hpp>
#include <boost/hana/core/when.hpp>
#include <cstddef>
namespace boost { namespace hana {
//! Returns the last `n` elements of a sequence, or the whole sequence
//! if the sequence has less than `n` elements.
//! @ingroup group-Sequence
//!
//! Given a `Sequence` `xs` and an `IntegralConstant` `n`, `take_back(xs, n)`
//! is a new sequence containing the last `n` elements of `xs`, in the
//! same order. If `length(xs) <= n`, the whole sequence is returned and
//! no error is triggered.
//!
//!
//! @param xs
//! The sequence to take the elements from.
//!
//! @param n
//! A non-negative `IntegralConstant` representing the number of elements
//! to keep in the resulting sequence.
//!
//!
//! Example
//! -------
//! @include example/take_back.cpp
#ifdef BOOST_HANA_DOXYGEN_INVOKED
constexpr auto take_back = [](auto&& xs, auto const& n) {
return tag-dispatched;
};
#else
template <typename S, typename = void>
struct take_back_impl : take_back_impl<S, when<true>> { };
struct take_back_t {
template <typename Xs, typename N>
constexpr auto operator()(Xs&& xs, N const& n) const;
};
BOOST_HANA_INLINE_VARIABLE constexpr take_back_t take_back{};
#endif
//! Equivalent to `take_back`; provided for convenience.
//! @ingroup group-Sequence
//!
//!
//! Example
//! -------
//! @include example/take_back_c.cpp
#ifdef BOOST_HANA_DOXYGEN_INVOKED
template <std::size_t n>
constexpr auto take_back_c = [](auto&& xs) {
return hana::take_back(forwarded(xs), hana::size_c<n>);
};
#else
template <std::size_t n>
struct take_back_c_t;
template <std::size_t n>
BOOST_HANA_INLINE_VARIABLE constexpr take_back_c_t<n> take_back_c{};
#endif
}} // end namespace boost::hana
#endif // !BOOST_HANA_FWD_TAKE_BACK_HPP
Mini Shell