parameter/aux_/always_true_predicate.hpp

0001 // Copyright Cromwell D. Enage 2019.
0002 // Distributed under the Boost Software License, Version 1.0.
0003 // (See accompanying file LICENSE_1_0.txt or copy at
0004 // http://www.boost.org/LICENSE_1_0.txt)
0005
0006 #ifndef BOOST_PARAMETER_AUX_ALWAYS_TRUE_PREDICATE_HPP
0007 #define BOOST_PARAMETER_AUX_ALWAYS_TRUE_PREDICATE_HPP
0008
0009 #include <boost/parameter/config.hpp>
0010 #include <boost/mpl/bool.hpp>
0011
0012 #if defined(BOOST_PARAMETER_HAS_PERFECT_FORWARDING)
0013 #if defined(BOOST_PARAMETER_CAN_USE_MP11)
0014 #include <boost/mp11/integral.hpp>
0015 #endif
0016 #else
0017 #include <boost/mpl/always.hpp>
0018 #endif
0019
0020 namespace boost { namespace parameter { namespace aux {
0021
0022 #if defined(BOOST_PARAMETER_HAS_PERFECT_FORWARDING)
0023     struct always_true_predicate
0024     {
0025         template <typename ...>
0026         struct apply
0027         {
0028             typedef ::boost::mpl::true_ type;
0029         };
0030
0031 #if defined(BOOST_PARAMETER_CAN_USE_MP11)
0032         template <typename ...>
0033         using fn = ::boost::mp11::mp_true;
0034 #endif
0035     };
0036 #else
0037     typedef ::boost::mpl::always< ::boost::mpl::true_> always_true_predicate;
0038 #endif  // BOOST_NO_CXX11_VARIADIC_TEMPLATES
0039 }}} // namespace boost::parameter::aux
0040
0041 #endif  // include guard
0042