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
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
|
/*!
@file
Defines `boost::hana::experimental::types`.
@copyright Louis Dionne 2013-2016
Distributed under the Boost Software License, Version 1.0.
(See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
*/
#ifndef BOOST_HANA_EXPERIMENTAL_TYPES_HPP
#define BOOST_HANA_EXPERIMENTAL_TYPES_HPP
#include <boost/hana/bool.hpp>
#include <boost/hana/concept/metafunction.hpp>
#include <boost/hana/config.hpp>
#include <boost/hana/detail/any_of.hpp>
#include <boost/hana/fwd/at.hpp>
#include <boost/hana/fwd/contains.hpp>
#include <boost/hana/fwd/core/tag_of.hpp>
#include <boost/hana/fwd/equal.hpp>
#include <boost/hana/fwd/is_empty.hpp>
#include <boost/hana/fwd/transform.hpp>
#include <boost/hana/fwd/unpack.hpp>
#include <boost/hana/type.hpp>
#include <cstddef>
#include <type_traits>
#include <utility>
BOOST_HANA_NAMESPACE_BEGIN
namespace experimental {
//! @ingroup group-experimental
//! Container optimized for holding types.
//!
//! It is often useful to manipulate a sequence that contains types
//! only, without any associated runtime value. This container allows
//! storing and manipulating pure types in a much more compile-time
//! efficient manner than using `hana::tuple`, which must assume that
//! its contents might have runtime values.
template <typename ...T>
struct types;
struct types_tag;
//////////////////////////////////////////////////////////////////////
template <typename ...T>
struct types { };
} // end namespace experimental
template <typename ...T>
struct tag_of<experimental::types<T...>> {
using type = experimental::types_tag;
};
// Foldable
template <>
struct unpack_impl<hana::experimental::types_tag> {
template <typename ...T, typename F, typename = typename std::enable_if<
!hana::Metafunction<F>::value
>::type>
static constexpr decltype(auto) apply(hana::experimental::types<T...> const&, F&& f) {
return static_cast<F&&>(f)(hana::type<T>{}...);
}
template <typename ...T, typename F, typename = typename std::enable_if<
hana::Metafunction<F>::value
>::type>
static constexpr hana::type<typename F::template apply<T...>::type>
apply(hana::experimental::types<T...> const&, F const&) { return {}; }
};
// Functor
template <>
struct transform_impl<hana::experimental::types_tag> {
template <typename ...T, typename F, typename = typename std::enable_if<
!hana::Metafunction<F>::value
>::type>
static constexpr auto apply(hana::experimental::types<T...> const&, F&& f)
-> hana::experimental::types<typename decltype(+f(hana::type<T>{}))::type...>
{ return {}; }
template <typename ...T, typename F, typename = typename std::enable_if<
hana::Metafunction<F>::value
>::type>
static constexpr hana::experimental::types<typename F::template apply<T>::type...>
apply(hana::experimental::types<T...> const&, F const&) { return {}; }
};
namespace types_detail {
template <std::size_t I, typename T>
struct elt { using type = T; };
template <typename Indices, typename ...T>
struct indexer;
template <std::size_t ...I, typename ...T>
struct indexer<std::index_sequence<I...>, T...>
: elt<I, T>...
{ };
template <std::size_t I, typename T>
elt<I, T> get_elt(elt<I, T> const&);
}
// Iterable
template <>
struct at_impl<hana::experimental::types_tag> {
template <typename ...T, typename N>
static constexpr auto
apply(hana::experimental::types<T...> const&, N const&) {
using Indexer = types_detail::indexer<std::make_index_sequence<sizeof...(T)>, T...>;
using Nth = typename decltype(types_detail::get_elt<N::value>(Indexer{}))::type;
return hana::type<Nth>{};
}
};
template <>
struct is_empty_impl<hana::experimental::types_tag> {
template <typename ...T>
static constexpr hana::bool_<sizeof...(T) == 0>
apply(hana::experimental::types<T...> const&)
{ return {}; }
};
template <>
struct drop_front_impl<hana::experimental::types_tag> {
template <std::size_t n, typename Indexer, std::size_t ...i>
static hana::experimental::types<
typename decltype(types_detail::get_elt<i + n>(Indexer{}))::type...
> helper(std::index_sequence<i...>);
template <typename ...T, typename N>
static constexpr auto
apply(hana::experimental::types<T...> const&, N const&) {
constexpr std::size_t n = N::value > sizeof...(T) ? sizeof...(T) : N::value;
using Indices = std::make_index_sequence<sizeof...(T) - n>;
using Indexer = types_detail::indexer<std::make_index_sequence<sizeof...(T)>, T...>;
return decltype(helper<n, Indexer>(Indices{})){};
}
};
// Searchable
template <>
struct contains_impl<hana::experimental::types_tag> {
template <typename U>
struct is_same_as {
template <typename T>
struct apply {
static constexpr bool value = std::is_same<U, T>::value;
};
};
template <typename ...T, typename U>
static constexpr auto apply(hana::experimental::types<T...> const&, U const&)
-> hana::bool_<
detail::any_of<is_same_as<typename U::type>::template apply, T...>::value
>
{ return {}; }
static constexpr hana::false_ apply(...) { return {}; }
};
// Comparable
template <>
struct equal_impl<hana::experimental::types_tag, hana::experimental::types_tag> {
template <typename Types>
static constexpr hana::true_ apply(Types const&, Types const&)
{ return {}; }
template <typename Ts, typename Us>
static constexpr hana::false_ apply(Ts const&, Us const&)
{ return {}; }
};
BOOST_HANA_NAMESPACE_END
#endif // !BOOST_HANA_EXPERIMENTAL_TYPES_HPP
|
