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RIntegerSequence.hxx
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1/// \file ROOT/RIntegerSequence.hxx
2/// \ingroup Base StdExt
3/// \author Enrico Guiraud <enrico.guiraud@cern.ch>
4/// \date 2018-04-06
5
6/*************************************************************************
7 * Copyright (C) 1995-2000, Rene Brun and Fons Rademakers. *
8 * All rights reserved. *
9 * *
10 * For the licensing terms see $ROOTSYS/LICENSE. *
11 * For the list of contributors see $ROOTSYS/README/CREDITS. *
12 *************************************************************************/
13
14#ifndef ROOT_RIntegerSequence
15#define ROOT_RIntegerSequence
16
17#include <RConfigure.h>
18#include "ROOT/RSpan.hxx"
19
20#ifdef R__HAS_STD_INDEX_SEQUENCE
21// no need to backport
22
23#include <utility>
24
25#else
26// backport libc++'s implementation (master branch, commit ece1de8)
27
28#include <cstddef>
29#include <type_traits>
30
31namespace ROOT {
32namespace Detail {
33
34template <class _IdxType, _IdxType... _Values>
36 template <template <class _OIdxType, _OIdxType...> class _ToIndexSeq, class _ToIndexType>
37 using __convert = _ToIndexSeq<_ToIndexType, _Values...>;
38};
39
40template<typename _Tp, size_t ..._Extra>
41struct __repeat;
42
43template<typename _Tp, _Tp ..._Np, size_t ..._Extra>
44struct __repeat<__integer_sequence<_Tp, _Np...>, _Extra...> {
45 typedef __integer_sequence<_Tp,
46 _Np...,
47 sizeof...(_Np) + _Np...,
48 2 * sizeof...(_Np) + _Np...,
49 3 * sizeof...(_Np) + _Np...,
50 4 * sizeof...(_Np) + _Np...,
51 5 * sizeof...(_Np) + _Np...,
52 6 * sizeof...(_Np) + _Np...,
53 7 * sizeof...(_Np) + _Np...,
54 _Extra...> type;
55};
56
57template<size_t _Np> struct __parity;
58template<size_t _Np> struct __make : __parity<_Np % 8>::template __pmake<_Np> {};
59
60template<> struct __make<0> { typedef __integer_sequence<size_t> type; };
61template<> struct __make<1> { typedef __integer_sequence<size_t, 0> type; };
62template<> struct __make<2> { typedef __integer_sequence<size_t, 0, 1> type; };
63template<> struct __make<3> { typedef __integer_sequence<size_t, 0, 1, 2> type; };
64template<> struct __make<4> { typedef __integer_sequence<size_t, 0, 1, 2, 3> type; };
65template<> struct __make<5> { typedef __integer_sequence<size_t, 0, 1, 2, 3, 4> type; };
68
69template <>
70struct __parity<0> {
71 template <size_t _Np>
72 struct __pmake : __repeat<typename __make<_Np / 8>::type> {
73 };
74};
75template<> struct __parity<1> { template<size_t _Np> struct __pmake : __repeat<typename __make<_Np / 8>::type, _Np - 1> {}; };
76template<> struct __parity<2> { template<size_t _Np> struct __pmake : __repeat<typename __make<_Np / 8>::type, _Np - 2, _Np - 1> {}; };
77template<> struct __parity<3> { template<size_t _Np> struct __pmake : __repeat<typename __make<_Np / 8>::type, _Np - 3, _Np - 2, _Np - 1> {}; };
78template<> struct __parity<4> { template<size_t _Np> struct __pmake : __repeat<typename __make<_Np / 8>::type, _Np - 4, _Np - 3, _Np - 2, _Np - 1> {}; };
79template<> struct __parity<5> { template<size_t _Np> struct __pmake : __repeat<typename __make<_Np / 8>::type, _Np - 5, _Np - 4, _Np - 3, _Np - 2, _Np - 1> {}; };
80template<> struct __parity<6> { template<size_t _Np> struct __pmake : __repeat<typename __make<_Np / 8>::type, _Np - 6, _Np - 5, _Np - 4, _Np - 3, _Np - 2, _Np - 1> {}; };
81template<> struct __parity<7> { template<size_t _Np> struct __pmake : __repeat<typename __make<_Np / 8>::type, _Np - 7, _Np - 6, _Np - 5, _Np - 4, _Np - 3, _Np - 2, _Np - 1> {}; };
82
83} // namespace Detail
84} // namespace ROOT
85
86namespace std {
87
88template <class _Tp, _Tp... _Ip>
89struct integer_sequence {
90 typedef _Tp value_type;
91 static_assert(is_integral<_Tp>::value, "std::integer_sequence can only be instantiated with an integral type");
92 static constexpr size_t size() noexcept { return sizeof...(_Ip); }
93};
94
95template <size_t... _Ip>
96using index_sequence = integer_sequence<size_t, _Ip...>;
97
98template <typename _Tp, _Tp _Np>
99using __make_integer_sequence_unchecked =
100 typename ROOT::Detail::__make<_Np>::type::template __convert<integer_sequence, _Tp>;
101
102template <class _Tp, _Tp _Ep>
103struct __make_integer_sequence_checked {
104 static_assert(is_integral<_Tp>::value, "std::make_integer_sequence can only be instantiated with an integral type");
105 static_assert(0 <= _Ep, "std::make_integer_sequence must have a non-negative sequence length");
106 // Workaround GCC bug by preventing bad installations when 0 <= _Ep
107 // https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68929
108 typedef __make_integer_sequence_unchecked<_Tp, 0 <= _Ep ? _Ep : 0> type;
109};
110
111template <class _Tp, _Tp _Ep>
112using __make_integer_sequence = typename __make_integer_sequence_checked<_Tp, _Ep>::type;
113
114template <class _Tp, _Tp _Np>
115using make_integer_sequence = __make_integer_sequence<_Tp, _Np>;
116
117template <size_t _Np>
118using make_index_sequence = make_integer_sequence<size_t, _Np>;
119
120template <class... _Tp>
121using index_sequence_for = make_index_sequence<sizeof...(_Tp)>;
122
123} // namespace std
124
125#endif // R__HAS_STD_INDEX_SEQUENCE
126#endif // ROOT_RIntegerSequence
int type
Definition: TGX11.cxx:120
Namespace for new ROOT classes and functions.
Definition: StringConv.hxx:21
_ToIndexSeq< _ToIndexType, _Values... > __convert
__integer_sequence< size_t > type
__integer_sequence< size_t, 0 > type
__integer_sequence< size_t, 0, 1 > type
__integer_sequence< size_t, 0, 1, 2 > type
__integer_sequence< size_t, 0, 1, 2, 3 > type
__integer_sequence< size_t, 0, 1, 2, 3, 4 > type
__integer_sequence< size_t, 0, 1, 2, 3, 4, 5 > type
__integer_sequence< size_t, 0, 1, 2, 3, 4, 5, 6 > type