58 lines
1.5 KiB
C++
58 lines
1.5 KiB
C++
/*!
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@file
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Forward declares `boost::hana::transform`.
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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_TRANSFORM_HPP
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#define BOOST_HANA_FWD_TRANSFORM_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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//! Map a function over a `Functor`.
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//! @ingroup group-Functor
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//!
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//!
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//! Signature
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//! ---------
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//! Given `F` a Functor, the signature is
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//! \f$
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//! \mathtt{transform} : F(T) \times (T \to U) \to F(U)
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//! \f$
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//!
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//! @param xs
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//! The structure to map `f` over.
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//!
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//! @param f
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//! A function called as `f(x)` on element(s) `x` of the structure,
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//! and returning a new value to replace `x` in the structure.
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//!
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//!
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//! Example
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//! -------
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//! @include example/transform.cpp
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#ifdef BOOST_HANA_DOXYGEN_INVOKED
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constexpr auto transform = [](auto&& xs, auto&& f) {
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return tag-dispatched;
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};
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#else
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template <typename Xs, typename = void>
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struct transform_impl : transform_impl<Xs, when<true>> { };
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struct transform_t {
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template <typename Xs, typename F>
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constexpr auto operator()(Xs&& xs, F&& f) const;
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};
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constexpr transform_t transform{};
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#endif
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BOOST_HANA_NAMESPACE_END
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#endif // !BOOST_HANA_FWD_TRANSFORM_HPP
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