hana/fwd/is_disjoint.hpp

0001 /*!
0002 @file
0003 Forward declares `boost::hana::is_disjoint`.
0004
0005 Copyright Louis Dionne 2013-2022
0006 Distributed under the Boost Software License, Version 1.0.
0007 (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
0008  */
0009
0010 #ifndef BOOST_HANA_FWD_IS_DISJOINT_HPP
0011 #define BOOST_HANA_FWD_IS_DISJOINT_HPP
0012
0013 #include <boost/hana/config.hpp>
0014 #include <boost/hana/core/when.hpp>
0015
0016
0017 namespace boost { namespace hana {
0018     //! Returns whether two `Searchable`s are disjoint.
0019     //! @ingroup group-Searchable
0020     //!
0021     //! Given two `Searchable`s `xs` and `ys`, `is_disjoint` returns a
0022     //! `Logical` representing whether the keys in `xs` are disjoint from
0023     //! the keys in `ys`, i.e. whether both structures have no keys in common.
0024     //!
0025     //!
0026     //! @param xs, ys
0027     //! Two `Searchable`s to test for disjointness.
0028     //!
0029     //!
0030     //! Example
0031     //! -------
0032     //! @include example/is_disjoint.cpp
0033 #ifdef BOOST_HANA_DOXYGEN_INVOKED
0034     constexpr auto is_disjoint = [](auto const& xs, auto const& ys) {
0035         return tag-dispatched;
0036     };
0037 #else
0038     template <typename S1, typename S2, typename = void>
0039     struct is_disjoint_impl : is_disjoint_impl<S1, S2, when<true>> { };
0040
0041     struct is_disjoint_t {
0042         template <typename Xs, typename Ys>
0043         constexpr auto operator()(Xs&& xs, Ys&& ys) const;
0044     };
0045
0046     BOOST_HANA_INLINE_VARIABLE constexpr is_disjoint_t is_disjoint{};
0047 #endif
0048 }} // end namespace boost::hana
0049
0050 #endif // !BOOST_HANA_FWD_IS_DISJOINT_HPP