3 Forward declares `boost::hana::less`.
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)
10 #ifndef BOOST_HANA_FWD_LESS_HPP
11 #define BOOST_HANA_FWD_LESS_HPP
13 #include <boost/hana/config.hpp>
14 #include <boost/hana/core/when.hpp>
15 #include <boost/hana/detail/nested_than_fwd.hpp>
18 BOOST_HANA_NAMESPACE_BEGIN
19 //! Returns a `Logical` representing whether `x` is less than `y`.
20 //! @ingroup group-Orderable
25 //! Given a Logical `Bool` and two Orderables `A` and `B` with a common
26 //! embedding, the signature is
27 //! @f$ \mathrm{less} : A \times B \to Bool @f$.
30 //! Two objects to compare.
35 //! @include example/less.cpp
36 #ifdef BOOST_HANA_DOXYGEN_INVOKED
37 constexpr auto less = [](auto&& x, auto&& y) {
38 return tag-dispatched;
41 template <typename T, typename U, typename = void>
42 struct less_impl : less_impl<T, U, when<true>> { };
44 struct less_t : detail::nested_than<less_t> {
45 template <typename X, typename Y>
46 constexpr auto operator()(X&& x, Y&& y) const;
49 constexpr less_t less{};
51 BOOST_HANA_NAMESPACE_END
53 #endif // !BOOST_HANA_FWD_LESS_HPP