1/*=============================================================================
2 Copyright (c) 2001-2014 Joel de Guzman
3 http://spirit.sourceforge.net/
4
5 Distributed under the Boost Software License, Version 1.0. (See accompanying
6 file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
7=============================================================================*/
8#if !defined(BOOST_SPIRIT_X3_VARIANT_HAS_SUBSTITUTE_APR_18_2014_925AM)
9#define BOOST_SPIRIT_X3_VARIANT_HAS_SUBSTITUTE_APR_18_2014_925AM
10
11#include <boost/spirit/home/x3/support/traits/is_substitute.hpp>
12#include <boost/mpl/find.hpp>
13
14namespace boost { namespace spirit { namespace x3 { namespace traits
15{
16 template <typename Variant, typename T>
17 struct variant_has_substitute_impl
18 {
19 // Find a type from the Variant that can be a substitute for T.
20 // return true_ if one is found, else false_
21
22 typedef Variant variant_type;
23 typedef typename variant_type::types types;
24 typedef typename mpl::end<types>::type end;
25
26 typedef typename mpl::find<types, T>::type iter_1;
27
28 typedef typename
29 mpl::eval_if<
30 is_same<iter_1, end>,
31 mpl::find_if<types, traits::is_substitute<T, mpl::_1>>,
32 mpl::identity<iter_1>
33 >::type
34 iter;
35
36 typedef mpl::not_<is_same<iter, end>> type;
37 };
38
39 template <typename Variant, typename T>
40 struct variant_has_substitute
41 : variant_has_substitute_impl<Variant, T>::type {};
42
43 template <typename T>
44 struct variant_has_substitute<unused_type, T> : mpl::true_ {};
45
46 template <typename T>
47 struct variant_has_substitute<unused_type const, T> : mpl::true_ {};
48
49}}}}
50
51#endif
52

source code of boost/libs/spirit/include/boost/spirit/home/x3/support/traits/variant_has_substitute.hpp