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1 | /*! |
2 | @file | |
3 | Forward declares `boost::hana::or_`. | |
4 | ||
5 | @copyright Louis Dionne 2013-2016 | |
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_OR_HPP | |
11 | #define BOOST_HANA_FWD_OR_HPP | |
12 | ||
13 | #include <boost/hana/config.hpp> | |
14 | #include <boost/hana/core/when.hpp> | |
15 | ||
16 | ||
17 | BOOST_HANA_NAMESPACE_BEGIN | |
18 | //! Return whether any of the arguments is true-valued. | |
19 | //! @ingroup group-Logical | |
20 | //! | |
21 | //! `or_` can be called with one argument or more. When called with | |
22 | //! two arguments, `or_` uses tag-dispatching to find the right | |
23 | //! implementation. Otherwise, | |
24 | //! @code | |
25 | //! or_(x) == x | |
26 | //! or_(x, y, ...z) == or_(or_(x, y), z...) | |
27 | //! @endcode | |
28 | //! | |
29 | //! | |
30 | //! Example | |
31 | //! ------- | |
32 | //! @include example/or.cpp | |
33 | #ifdef BOOST_HANA_DOXYGEN_INVOKED | |
34 | constexpr auto or_ = [](auto&& x, auto&& ...y) -> decltype(auto) { | |
35 | return tag-dispatched; | |
36 | }; | |
37 | #else | |
38 | template <typename L, typename = void> | |
39 | struct or_impl : or_impl<L, when<true>> { }; | |
40 | ||
41 | struct or_t { | |
42 | template <typename X, typename Y> | |
43 | constexpr decltype(auto) operator()(X&& x, Y&& y) const; | |
44 | ||
45 | template <typename X, typename ...Y> | |
46 | constexpr decltype(auto) operator()(X&& x, Y&& ...y) const; | |
47 | }; | |
48 | ||
49 | constexpr or_t or_{}; | |
50 | #endif | |
51 | BOOST_HANA_NAMESPACE_END | |
52 | ||
53 | #endif // !BOOST_HANA_FWD_OR_HPP |