74 lines
2.4 KiB
C++
74 lines
2.4 KiB
C++
/*!
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@file
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Forward declares `boost::hana::contains` and `boost::hana::in`.
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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_CONTAINS_HPP
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#define BOOST_HANA_FWD_CONTAINS_HPP
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#include <boost/hana/config.hpp>
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#include <boost/hana/core/when.hpp>
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#include <boost/hana/functional/flip.hpp>
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#include <boost/hana/functional/infix.hpp>
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BOOST_HANA_NAMESPACE_BEGIN
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//! Returns whether the key occurs in the structure.
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//! @ingroup group-Searchable
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//!
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//! Given a `Searchable` structure `xs` and a `key`, `contains` returns
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//! whether any of the keys of the structure is equal to the given `key`.
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//! If the structure is not finite, an equal key has to appear at a finite
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//! position in the structure for this method to finish. For convenience,
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//! `contains` can also be applied in infix notation.
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//!
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//!
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//! @param xs
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//! The structure to search.
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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.
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//!
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//!
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//! Example
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//! -------
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//! @include example/contains.cpp
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#ifdef BOOST_HANA_DOXYGEN_INVOKED
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constexpr auto contains = [](auto&& xs, auto&& 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 contains_impl : contains_impl<S, when<true>> { };
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struct contains_t {
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template <typename Xs, typename Key>
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constexpr auto operator()(Xs&& xs, Key&& key) const;
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};
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constexpr auto contains = hana::infix(contains_t{});
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#endif
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//! Return whether the key occurs in the structure.
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//! @ingroup group-Searchable
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//!
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//! Specifically, this is equivalent to `contains`, except `in` takes its
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//! arguments in reverse order. Like `contains`, `in` can also be applied
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//! in infix notation for increased expressiveness. This function is not a
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//! method that can be overriden; it is just a convenience function
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//! provided with the concept.
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//!
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//!
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//! Example
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//! -------
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//! @include example/in.cpp
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constexpr auto in = hana::infix(hana::flip(hana::contains));
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BOOST_HANA_NAMESPACE_END
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#endif // !BOOST_HANA_FWD_CONTAINS_HPP
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