| 1 | /*! |
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| 2 | @file |
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| 3 | Forward declares `boost::hana::find`. |
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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_FIND_HPP |
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| 11 | #define BOOST_HANA_FWD_FIND_HPP |
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| 12 | |
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| 13 | #include <boost/hana/config.hpp> |
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| 14 | #include <boost/hana/core/when.hpp> |
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| 15 | |
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| 16 | |
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| 17 | namespace boost { namespace hana { |
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| 18 | //! Finds the value associated to the given key in a structure. |
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| 19 | //! @ingroup group-Searchable |
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| 20 | //! |
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| 21 | //! Given a `key` and a `Searchable` structure, `find` returns the `just` |
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| 22 | //! the first value whose key is equal to the given `key`, or `nothing` if |
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| 23 | //! there is no such key. Comparison is done with `equal`. `find` satisfies |
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| 24 | //! the following: |
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| 25 | //! @code |
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| 26 | //! find(xs, key) == find_if(xs, equal.to(key)) |
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| 27 | //! @endcode |
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| 28 | //! |
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| 29 | //! |
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| 30 | //! @param xs |
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| 31 | //! The structure to be searched. |
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| 32 | //! |
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| 33 | //! @param key |
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| 34 | //! A key to be searched for in the structure. The key has to be |
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| 35 | //! `Comparable` with the other keys of the structure. In the current |
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| 36 | //! version of the library, the comparison of `key` with any other key |
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| 37 | //! of the structure must return a compile-time `Logical`. |
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| 38 | //! |
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| 39 | //! |
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| 40 | //! Example |
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| 41 | //! ------- |
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| 42 | //! @include example/find.cpp |
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| 43 | #ifdef BOOST_HANA_DOXYGEN_INVOKED |
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| 44 | constexpr auto find = [](auto&& xs, auto const& key) { |
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| 45 | return tag-dispatched; |
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| 46 | }; |
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| 47 | #else |
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| 48 | template <typename S, typename = void> |
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| 49 | struct find_impl : find_impl<S, when<true>> { }; |
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| 50 | |
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| 51 | struct find_t { |
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| 52 | template <typename Xs, typename Key> |
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| 53 | constexpr auto operator()(Xs&& xs, Key const& key) const; |
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| 54 | }; |
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| 55 | |
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| 56 | BOOST_HANA_INLINE_VARIABLE constexpr find_t find{}; |
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| 57 | #endif |
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| 58 | }} // end namespace boost::hana |
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| 59 | |
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| 60 | #endif // !BOOST_HANA_FWD_FIND_HPP |
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| 61 | |
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