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 Hu Chunming
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/*!
@file
Forward declares `boost::hana::lift`.
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_LIFT_HPP
#define BOOST_HANA_FWD_LIFT_HPP
#include <boost/hana/config.hpp>
#include <boost/hana/core/when.hpp>
namespace boost { namespace hana {
//! Lift a value into an `Applicative` structure.
//! @ingroup group-Applicative
//!
//! `lift<A>` takes a normal value and embeds it into a structure whose
//! shape is represented by the `A` `Applicative`. Note that the value
//! may be a function, in which case the created structure may be
//! `ap`plied to another `Applicative` structure containing values.
//!
//!
//! Signature
//! ---------
//! Given an Applicative `A`, the signature is
//! @f$ \mathtt{lift}_A : T \to A(T) @f$.
//!
//! @tparam A
//! A tag representing the `Applicative` into which the value is lifted.
//!
//! @param x
//! The value to lift into the applicative.
//!
//!
//! Example
//! -------
//! @include example/lift.cpp
#ifdef BOOST_HANA_DOXYGEN_INVOKED
template <typename A>
constexpr auto lift = [](auto&& x) {
return tag-dispatched;
};
#else
template <typename A, typename = void>
struct lift_impl : lift_impl<A, when<true>> { };
template <typename A>
struct lift_t {
template <typename X>
constexpr auto operator()(X&& x) const;
};
template <typename A>
BOOST_HANA_INLINE_VARIABLE constexpr lift_t<A> lift{};
#endif
}} // end namespace boost::hana
#endif // !BOOST_HANA_FWD_LIFT_HPP
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