61 lines
1.8 KiB
C++
61 lines
1.8 KiB
C++
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/*!
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@file
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Forward declares `boost::hana::find`.
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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_FIND_HPP
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#define BOOST_HANA_FWD_FIND_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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//! Finds the value associated to the given key in a structure.
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//! @ingroup group-Searchable
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//!
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//! Given a `key` and a `Searchable` structure, `find` returns the `just`
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//! the first value whose key is equal to the given `key`, or `nothing` if
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//! there is no such key. Comparison is done with `equal`. `find` satisfies
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//! the following:
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//! @code
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//! find(xs, key) == find_if(xs, equal.to(key))
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//! @endcode
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//!
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//!
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//! @param xs
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//! The structure to be searched.
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//!
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//! @param key
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//! A key to be searched for in the structure. The key has to be
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//! `Comparable` with the other keys of the structure. In the current
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//! version of the library, the comparison of `key` with any other key
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//! of the structure must return a compile-time `Logical`.
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//!
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//!
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//! Example
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//! -------
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//! @include example/find.cpp
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#ifdef BOOST_HANA_DOXYGEN_INVOKED
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constexpr auto find = [](auto&& xs, auto const& key) {
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return tag-dispatched;
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};
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#else
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template <typename S, typename = void>
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struct find_impl : find_impl<S, when<true>> { };
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struct find_t {
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template <typename Xs, typename Key>
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constexpr auto operator()(Xs&& xs, Key const& key) const;
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};
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constexpr find_t find{};
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#endif
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BOOST_HANA_NAMESPACE_END
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#endif // !BOOST_HANA_FWD_FIND_HPP
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