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
|
/*!
@file
Adapts `std::integer_sequence` for use with Hana.
@copyright Louis Dionne 2013-2017
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_EXT_STD_INTEGER_SEQUENCE_HPP
#define BOOST_HANA_EXT_STD_INTEGER_SEQUENCE_HPP
#include <boost/hana/bool.hpp>
#include <boost/hana/config.hpp>
#include <boost/hana/detail/fast_and.hpp>
#include <boost/hana/ext/std/integral_constant.hpp>
#include <boost/hana/fwd/at.hpp>
#include <boost/hana/fwd/core/tag_of.hpp>
#include <boost/hana/fwd/drop_front.hpp>
#include <boost/hana/fwd/equal.hpp>
#include <boost/hana/fwd/is_empty.hpp>
#include <boost/hana/fwd/unpack.hpp>
#include <cstddef>
#include <type_traits>
#include <utility>
#ifdef BOOST_HANA_DOXYGEN_INVOKED
namespace std {
//! @ingroup group-ext-std
//! Adaptation of `std::integer_sequence` for Hana.
//!
//!
//!
//! Modeled concepts
//! ----------------
//! 1. `Comparable`\n
//! Two `std::integer_sequence`s are equal if and only if they have the
//! same number of elements, and if corresponding elements compare equal.
//! The types of the elements held in both `integer_sequence`s may be
//! different, as long as they can be compared.
//! @include example/ext/std/integer_sequence/comparable.cpp
//!
//! 2. `Foldable`\n
//! Folding an `integer_sequence` is equivalent to folding a sequence of
//! `std::integral_constant`s with the corresponding types.
//! @include example/ext/std/integer_sequence/foldable.cpp
//!
//! 3. `Iterable`\n
//! Iterating over an `integer_sequence` is equivalent to iterating over
//! a sequence of the corresponding `std::integral_constant`s.
//! @include example/ext/std/integer_sequence/iterable.cpp
//!
//! 4. `Searchable`\n
//! Searching through an `integer_sequence` is equivalent to searching
//! through the corresponding sequence of `std::integral_constant`s.
//! @include example/ext/std/integer_sequence/searchable.cpp
template <typename T, T ...v>
struct integer_sequence { };
}
#endif
BOOST_HANA_NAMESPACE_BEGIN
namespace ext { namespace std { struct integer_sequence_tag; }}
template <typename T, T ...v>
struct tag_of<std::integer_sequence<T, v...>> {
using type = ext::std::integer_sequence_tag;
};
//////////////////////////////////////////////////////////////////////////
// Comparable
//////////////////////////////////////////////////////////////////////////
template <>
struct equal_impl<ext::std::integer_sequence_tag, ext::std::integer_sequence_tag> {
template <typename X, X ...xs, typename Y, Y ...ys>
static constexpr hana::bool_<detail::fast_and<(xs == ys)...>::value>
apply(std::integer_sequence<X, xs...> const&, std::integer_sequence<Y, ys...> const&)
{ return {}; }
template <typename Xs, typename Ys>
static constexpr hana::false_ apply(Xs const&, Ys const&, ...)
{ return {}; }
};
//////////////////////////////////////////////////////////////////////////
// Foldable
//////////////////////////////////////////////////////////////////////////
template <>
struct unpack_impl<ext::std::integer_sequence_tag> {
template <typename T, T ...v, typename F>
static constexpr decltype(auto)
apply(std::integer_sequence<T, v...> const&, F&& f) {
return static_cast<F&&>(f)(std::integral_constant<T, v>{}...);
}
};
//////////////////////////////////////////////////////////////////////////
// Iterable
//////////////////////////////////////////////////////////////////////////
template <>
struct at_impl<ext::std::integer_sequence_tag> {
template <typename T, T ...v, typename N>
static constexpr auto apply(std::integer_sequence<T, v...> const&, N const&) {
constexpr std::size_t n = N::value;
constexpr T values_[] = {v...};
return std::integral_constant<T, values_[n]>{};
}
};
template <>
struct drop_front_impl<ext::std::integer_sequence_tag> {
template <std::size_t n, typename T, T ...t, std::size_t ...i>
static constexpr auto drop_front_helper(std::integer_sequence<T, t...>,
std::index_sequence<i...>)
{
constexpr T ts[sizeof...(t)+1] = {t...}; // avoid 0-sized array
return std::integer_sequence<T, ts[n + i]...>{};
}
template <typename T, T ...t, typename N>
static constexpr auto apply(std::integer_sequence<T, t...> ts, N const&) {
constexpr std::size_t n = N::value;
constexpr std::size_t len = sizeof...(t);
return drop_front_helper<n>(ts,
std::make_index_sequence<(n < len ? len - n : 0)>{});
}
};
template <>
struct is_empty_impl<ext::std::integer_sequence_tag> {
template <typename T, T ...xs>
static constexpr auto apply(std::integer_sequence<T, xs...> const&)
{ return hana::bool_c<sizeof...(xs) == 0>; }
};
BOOST_HANA_NAMESPACE_END
#endif // !BOOST_HANA_EXT_STD_INTEGER_SEQUENCE_HPP
|
