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1 | /*! |
2 | @file | |
3 | Forward declares `boost::hana::contains` and `boost::hana::in`. | |
4 | ||
b32b8144 | 5 | @copyright Louis Dionne 2013-2017 |
7c673cae FG |
6 | Distributed under the Boost Software License, Version 1.0. |
7 | (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt) | |
8 | */ | |
9 | ||
10 | #ifndef BOOST_HANA_FWD_CONTAINS_HPP | |
11 | #define BOOST_HANA_FWD_CONTAINS_HPP | |
12 | ||
13 | #include <boost/hana/config.hpp> | |
14 | #include <boost/hana/core/when.hpp> | |
15 | #include <boost/hana/functional/flip.hpp> | |
16 | #include <boost/hana/functional/infix.hpp> | |
17 | ||
18 | ||
19 | BOOST_HANA_NAMESPACE_BEGIN | |
20 | //! Returns whether the key occurs in the structure. | |
21 | //! @ingroup group-Searchable | |
22 | //! | |
23 | //! Given a `Searchable` structure `xs` and a `key`, `contains` returns | |
24 | //! whether any of the keys of the structure is equal to the given `key`. | |
25 | //! If the structure is not finite, an equal key has to appear at a finite | |
26 | //! position in the structure for this method to finish. For convenience, | |
27 | //! `contains` can also be applied in infix notation. | |
28 | //! | |
29 | //! | |
30 | //! @param xs | |
31 | //! The structure to search. | |
32 | //! | |
33 | //! @param key | |
34 | //! A key to be searched for in the structure. The key has to be | |
35 | //! `Comparable` with the other keys of the structure. | |
36 | //! | |
37 | //! | |
38 | //! Example | |
39 | //! ------- | |
40 | //! @include example/contains.cpp | |
41 | #ifdef BOOST_HANA_DOXYGEN_INVOKED | |
42 | constexpr auto contains = [](auto&& xs, auto&& key) { | |
43 | return tag-dispatched; | |
44 | }; | |
45 | #else | |
46 | template <typename S, typename = void> | |
47 | struct contains_impl : contains_impl<S, when<true>> { }; | |
48 | ||
49 | struct contains_t { | |
50 | template <typename Xs, typename Key> | |
51 | constexpr auto operator()(Xs&& xs, Key&& key) const; | |
52 | }; | |
53 | ||
54 | constexpr auto contains = hana::infix(contains_t{}); | |
55 | #endif | |
56 | ||
57 | //! Return whether the key occurs in the structure. | |
58 | //! @ingroup group-Searchable | |
59 | //! | |
60 | //! Specifically, this is equivalent to `contains`, except `in` takes its | |
61 | //! arguments in reverse order. Like `contains`, `in` can also be applied | |
62 | //! in infix notation for increased expressiveness. This function is not a | |
63 | //! method that can be overriden; it is just a convenience function | |
64 | //! provided with the concept. | |
65 | //! | |
66 | //! | |
67 | //! Example | |
68 | //! ------- | |
69 | //! @include example/in.cpp | |
70 | constexpr auto in = hana::infix(hana::flip(hana::contains)); | |
71 | BOOST_HANA_NAMESPACE_END | |
72 | ||
73 | #endif // !BOOST_HANA_FWD_CONTAINS_HPP |