1 /*!
2 @file
3 Forward declares `boost::hana::find`.
4 
5 @copyright Louis Dionne 2013-2017
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_FIND_HPP
11 #define BOOST_HANA_FWD_FIND_HPP
12 
13 #include <boost/hana/config.hpp>
14 #include <boost/hana/core/when.hpp>
15 
16 
17 BOOST_HANA_NAMESPACE_BEGIN
18     //! Finds the value associated to the given key in a structure.
19     //! @ingroup group-Searchable
20     //!
21     //! Given a `key` and a `Searchable` structure, `find` returns the `just`
22     //! the first value whose key is equal to the given `key`, or `nothing` if
23     //! there is no such key. Comparison is done with `equal`. `find` satisfies
24     //! the following:
25     //! @code
26     //!     find(xs, key) == find_if(xs, equal.to(key))
27     //! @endcode
28     //!
29     //!
30     //! @param xs
31     //! The structure to be searched.
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. In the current
36     //! version of the library, the comparison of `key` with any other key
37     //! of the structure must return a compile-time `Logical`.
38     //!
39     //!
40     //! Example
41     //! -------
42     //! @include example/find.cpp
43 #ifdef BOOST_HANA_DOXYGEN_INVOKED
__anon9b4500460102(auto&& xs, auto const& key) 44     constexpr auto find = [](auto&& xs, auto const& key) {
45         return tag-dispatched;
46     };
47 #else
48     template <typename S, typename = void>
49     struct find_impl : find_impl<S, when<true>> { };
50 
51     struct find_t {
52         template <typename Xs, typename Key>
53         constexpr auto operator()(Xs&& xs, Key const& key) const;
54     };
55 
56     constexpr find_t find{};
57 #endif
58 BOOST_HANA_NAMESPACE_END
59 
60 #endif // !BOOST_HANA_FWD_FIND_HPP
61