| 1 | /*! |
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| 2 | @file |
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| 3 | Forward declares `boost::hana::fuse`. |
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| 4 | |
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| 5 | Copyright Louis Dionne 2013-2022 |
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| 6 | Distributed under the Boost Software License, Version 1.0. |
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| 7 | (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt) |
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| 8 | */ |
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| 9 | |
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| 10 | #ifndef BOOST_HANA_FWD_FUSE_HPP |
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| 11 | #define BOOST_HANA_FWD_FUSE_HPP |
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| 12 | |
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| 13 | #include <boost/hana/config.hpp> |
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| 14 | |
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| 15 | |
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| 16 | namespace boost { namespace hana { |
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| 17 | //! Transform a function taking multiple arguments into a function that |
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| 18 | //! can be called with a compile-time `Foldable`. |
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| 19 | //! @ingroup group-Foldable |
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| 20 | //! |
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| 21 | //! |
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| 22 | //! This function is provided for convenience as a different way of |
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| 23 | //! calling `unpack`. Specifically, `fuse(f)` is a function such that |
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| 24 | //! @code |
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| 25 | //! fuse(f)(foldable) == unpack(foldable, f) |
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| 26 | //! == f(x...) |
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| 27 | //! @endcode |
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| 28 | //! where `x...` are the elements in the foldable. This function is |
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| 29 | //! useful when one wants to create a function that accepts a foldable |
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| 30 | //! which is not known yet. |
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| 31 | //! |
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| 32 | //! @note |
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| 33 | //! This function is not tag-dispatched; customize `unpack` instead. |
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| 34 | //! |
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| 35 | //! |
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| 36 | //! Example |
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| 37 | //! ------- |
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| 38 | //! @include example/fuse.cpp |
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| 39 | #ifdef BOOST_HANA_DOXYGEN_INVOKED |
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| 40 | constexpr auto fuse = [](auto&& f) { |
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| 41 | return [perfect-capture](auto&& xs) -> decltype(auto) { |
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| 42 | return unpack(forwarded(xs), forwarded(f)); |
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| 43 | }; |
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| 44 | }; |
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| 45 | #else |
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| 46 | struct fuse_t { |
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| 47 | template <typename F> |
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| 48 | constexpr auto operator()(F&& f) const; |
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| 49 | }; |
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| 50 | |
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| 51 | BOOST_HANA_INLINE_VARIABLE constexpr fuse_t fuse{}; |
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| 52 | #endif |
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| 53 | }} // end namespace boost::hana |
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| 54 | |
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| 55 | #endif // !BOOST_HANA_FWD_FUSE_HPP |
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| 56 | |
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