/usr/include/boost/hana/fwd
Edit: /usr/include/boost/hana/fwd/empty.hpp (1306B)
/*!
@file
Forward declares `boost::hana::empty`.
@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_EMPTY_HPP
#define BOOST_HANA_FWD_EMPTY_HPP
#include
#include
BOOST_HANA_NAMESPACE_BEGIN
//! Identity of the monadic combination `concat`.
//! @ingroup group-MonadPlus
//!
//! Signature
//! ---------
//! Given a MonadPlus `M`, the signature is
//! @f$ \mathtt{empty}_M : \emptyset \to M(T) @f$.
//!
//! @tparam M
//! The tag of the monadic structure to return. This must be
//! a model of the MonadPlus concept.
//!
//!
//! Example
//! -------
//! @include example/empty.cpp
#ifdef BOOST_HANA_DOXYGEN_INVOKED
template
constexpr auto empty = []() {
return tag-dispatched;
};
#else
template
struct empty_impl : empty_impl> { };
template
struct empty_t {
constexpr auto operator()() const;
};
template
constexpr empty_t empty{};
#endif
BOOST_HANA_NAMESPACE_END
#endif // !BOOST_HANA_FWD_EMPTY_HPP