/usr/include/boost/hana/fwd
Edit: /usr/include/boost/hana/fwd/back.hpp (1355B)
/*!
@file
Forward declares `boost::hana::back`.
@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_FWD_BACK_HPP
#define BOOST_HANA_FWD_BACK_HPP
#include
#include
BOOST_HANA_NAMESPACE_BEGIN
//! Returns the last element of a non-empty and finite iterable.
//! @ingroup group-Iterable
//!
//! Given a non-empty and finite iterable `xs` with a linearization of
//! `[x1, ..., xN]`, `back(xs)` is equal to `xN`. Equivalently, `back(xs)`
//! must be equivalent to `at_c(xs)`, and that regardless of the
//! value category of `xs` (`back` must respect the reference semantics
//! of `at`).
//!
//!
//! Example
//! -------
//! @include example/back.cpp
#ifdef BOOST_HANA_DOXYGEN_INVOKED
constexpr auto back = [](auto&& xs) -> decltype(auto) {
return tag-dispatched;
};
#else
template
struct back_impl : back_impl> { };
struct back_t {
template
constexpr decltype(auto) operator()(Xs&& xs) const;
};
constexpr back_t back{};
#endif
BOOST_HANA_NAMESPACE_END
#endif // !BOOST_HANA_FWD_BACK_HPP