60 lines
1.6 KiB
C++
60 lines
1.6 KiB
C++
/*!
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@file
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Forward declares `boost::hana::lift`.
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@copyright Louis Dionne 2013-2016
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Distributed under the Boost Software License, Version 1.0.
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(See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
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*/
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#ifndef BOOST_HANA_FWD_LIFT_HPP
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#define BOOST_HANA_FWD_LIFT_HPP
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#include <boost/hana/config.hpp>
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#include <boost/hana/core/when.hpp>
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BOOST_HANA_NAMESPACE_BEGIN
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//! Lift a value into an `Applicative` structure.
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//! @ingroup group-Applicative
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//!
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//! `lift<A>` takes a normal value and embeds it into a structure whose
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//! shape is represented by the `A` `Applicative`. Note that the value
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//! may be a function, in which case the created structure may be
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//! `ap`plied to another `Applicative` structure containing values.
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//!
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//!
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//! Signature
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//! ---------
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//! Given an Applicative `A`, the signature is
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//! @f$ \mathtt{lift}_A : T \to A(T) @f$.
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//!
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//! @tparam A
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//! A tag representing the `Applicative` into which the value is lifted.
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//!
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//! @param x
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//! The value to lift into the applicative.
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//!
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//!
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//! Example
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//! -------
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//! @include example/lift.cpp
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#ifdef BOOST_HANA_DOXYGEN_INVOKED
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template <typename A>
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constexpr auto lift = [](auto&& x) {
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return tag-dispatched;
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};
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#else
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template <typename A, typename = void>
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struct lift_impl : lift_impl<A, when<true>> { };
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template <typename A>
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struct lift_t;
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template <typename A>
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constexpr lift_t<A> lift{};
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#endif
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BOOST_HANA_NAMESPACE_END
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#endif // !BOOST_HANA_FWD_LIFT_HPP
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