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Diffstat (limited to 'boost/hana/fwd/lift.hpp')
| -rw-r--r-- | boost/hana/fwd/lift.hpp | 59 |
1 files changed, 59 insertions, 0 deletions
diff --git a/boost/hana/fwd/lift.hpp b/boost/hana/fwd/lift.hpp new file mode 100644 index 0000000000..2f30fd68d5 --- /dev/null +++ b/boost/hana/fwd/lift.hpp @@ -0,0 +1,59 @@ +/*! +@file +Forward declares `boost::hana::lift`. + +@copyright Louis Dionne 2013-2016 +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> + + +BOOST_HANA_NAMESPACE_BEGIN + //! 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 A> + constexpr lift_t<A> lift{}; +#endif +BOOST_HANA_NAMESPACE_END + +#endif // !BOOST_HANA_FWD_LIFT_HPP |