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/*============================================================================= Copyright (c) 2001-2014 Joel de Guzman http://spirit.sourceforge.net/ Distributed under the Boost Software License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) =============================================================================*/ #if !defined(BOOST_SPIRIT_X3_VARIANT_HAS_SUBSTITUTE_APR_18_2014_925AM) #define BOOST_SPIRIT_X3_VARIANT_HAS_SUBSTITUTE_APR_18_2014_925AM #include <boost/spirit/home/x3/support/traits/is_substitute.hpp> #include <boost/mpl/find.hpp> namespace boost { namespace spirit { namespace x3 { namespace traits { template <typename Variant, typename T> struct variant_has_substitute_impl { // Find a type from the Variant that can be a substitute for T. // return true_ if one is found, else false_ typedef Variant variant_type; typedef typename variant_type::types types; typedef typename mpl::end<types>::type end; typedef typename mpl::find<types, T>::type iter_1; typedef typename mpl::eval_if< is_same<iter_1, end>, mpl::find_if<types, traits::is_substitute<T, mpl::_1>>, mpl::identity<iter_1> >::type iter; typedef mpl::not_<is_same<iter, end>> type; }; template <typename Variant, typename T> struct variant_has_substitute : variant_has_substitute_impl<Variant, T>::type {}; template <typename T> struct variant_has_substitute<unused_type, T> : mpl::true_ {}; template <typename T> struct variant_has_substitute<unused_type const, T> : mpl::true_ {}; }}}} #endif