blob: 65568b0265bb25b3ca8b2f71d8579a4de70997ef (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
|
/*=============================================================================
Copyright (c) 2001-2014 Joel de Guzman
Copyright (c) 2001-2011 Hartmut Kaiser
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_OPTIONAL_TRAITS_FEBRUARY_06_2007_1001AM)
#define BOOST_SPIRIT_X3_OPTIONAL_TRAITS_FEBRUARY_06_2007_1001AM
#if defined(_MSC_VER)
#pragma once
#endif
#include <boost/spirit/home/x3/support/unused.hpp>
#include <boost/optional/optional.hpp>
#include <boost/mpl/identity.hpp>
namespace boost { namespace spirit { namespace x3 { namespace traits
{
///////////////////////////////////////////////////////////////////////////
template <typename T, typename Enable = void>
struct is_optional
: mpl::false_
{};
template <typename T>
struct is_optional<boost::optional<T>>
: mpl::true_
{};
///////////////////////////////////////////////////////////////////////////
// build_optional
//
// Build a boost::optional from T. Return unused_type if T is unused_type.
///////////////////////////////////////////////////////////////////////////
template <typename T>
struct build_optional
{
typedef boost::optional<T> type;
};
template <typename T>
struct build_optional<boost::optional<T> >
{
typedef boost::optional<T> type;
};
template <>
struct build_optional<unused_type>
{
typedef unused_type type;
};
///////////////////////////////////////////////////////////////////////////
// optional_value
//
// Get the optional's value_type. Handles unused_type as well.
///////////////////////////////////////////////////////////////////////////
template <typename T>
struct optional_value : mpl::identity<T> {};
template <typename T>
struct optional_value<boost::optional<T> >
: mpl::identity<T> {};
template <>
struct optional_value<unused_type>
: mpl::identity<unused_type> {};
template <>
struct optional_value<unused_type const>
: mpl::identity<unused_type> {};
}}}}
#endif
|
