libstdc++: slice_array.h Source File

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slice_array.h
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1// The template and inlines for the -*- C++ -*- slice_array class.
2
3// Copyright (C) 1997-2026 Free Software Foundation, Inc.
4//
5// This file is part of the GNU ISO C++ Library. This library is free
6// software; you can redistribute it and/or modify it under the
7// terms of the GNU General Public License as published by the
8// Free Software Foundation; either version 3, or (at your option)
9// any later version.
10
11// This library is distributed in the hope that it will be useful,
12// but WITHOUT ANY WARRANTY; without even the implied warranty of
13// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14// GNU General Public License for more details.
15
16// Under Section 7 of GPL version 3, you are granted additional
17// permissions described in the GCC Runtime Library Exception, version
18// 3.1, as published by the Free Software Foundation.
19
20// You should have received a copy of the GNU General Public License and
21// a copy of the GCC Runtime Library Exception along with this program;
22// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
23// <http://www.gnu.org/licenses/>.
24
25/** @file bits/slice_array.h
26 * This is an internal header file, included by other library headers.
27 * Do not attempt to use it directly. @headername{valarray}
28 */
29
30// Written by Gabriel Dos Reis <Gabriel.Dos-Reis@DPTMaths.ENS-Cachan.Fr>
31
32#ifndef _SLICE_ARRAY_H
33#define _SLICE_ARRAY_H 1
34
35#ifdef _GLIBCXX_SYSHDR
36#pragma GCC system_header
37#endif
38
39namespace std _GLIBCXX_VISIBILITY(default)
40{
41_GLIBCXX_BEGIN_NAMESPACE_VERSION
42
43 /**
44 * @addtogroup numeric_arrays
45 * @{
46 */
47
48 /**
49 * @brief Class defining one-dimensional subset of an array.
50 *
51 * The slice class represents a one-dimensional subset of an array,
52 * specified by three parameters: start offset, size, and stride. The
53 * start offset is the index of the first element of the array that is part
54 * of the subset. The size is the total number of elements in the subset.
55 * Stride is the distance between each successive array element to include
56 * in the subset.
57 *
58 * For example, with an array of size 10, and a slice with offset 1, size 3
59 * and stride 2, the subset consists of array elements 1, 3, and 5.
60 */
61 class slice
62 {
63 public:
64 /// Construct an empty slice.
65 slice();
66
67 /**
68 * @brief Construct a slice.
69 *
70 * @param __o Offset in array of first element.
71 * @param __d Number of elements in slice.
72 * @param __s Stride between array elements.
73 */
74 slice(size_t __o, size_t __d, size_t __s);
75
76 /// Return array offset of first slice element.
77 size_t start() const;
78 /// Return size of slice.
79 size_t size() const;
80 /// Return array stride of slice.
81 size_t stride() const;
82
83#if __cpp_impl_three_way_comparison >= 201907L
84 /// Equality comparison
85 friend bool operator==(const slice&, const slice&) = default;
86#endif
87
88 private:
89 size_t _M_off; // offset
90 size_t _M_sz; // size
91 size_t _M_st; // stride unit
92 };
93
94 // _GLIBCXX_RESOLVE_LIB_DEFECTS
95 // 543. valarray slice default constructor
96 inline
97 slice::slice()
98 : _M_off(0), _M_sz(0), _M_st(0) {}
99
100 inline
101 slice::slice(size_t __o, size_t __d, size_t __s)
102 : _M_off(__o), _M_sz(__d), _M_st(__s) {}
103
104 inline size_t
105 slice::start() const
106 { return _M_off; }
107
108 inline size_t
109 slice::size() const
110 { return _M_sz; }
111
112 inline size_t
113 slice::stride() const
114 { return _M_st; }
115
116 /**
117 * @brief Reference to one-dimensional subset of an array.
118 *
119 * A slice_array is a reference to the actual elements of an array
120 * specified by a slice. The way to get a slice_array is to call
121 * operator[](slice) on a valarray. The returned slice_array then permits
122 * carrying operations out on the referenced subset of elements in the
123 * original valarray. For example, operator+=(valarray) will add values
124 * to the subset of elements in the underlying valarray this slice_array
125 * refers to.
126 *
127 * @param Tp Element type.
128 */
129 template<typename _Tp>
130 class slice_array
131 {
132 public:
133 typedef _Tp value_type;
134
135 // _GLIBCXX_RESOLVE_LIB_DEFECTS
136 // 253. valarray helper functions are almost entirely useless
137
138 /// Copy constructor. Both slices refer to the same underlying array.
139 slice_array(const slice_array&);
140
141 /// Assignment operator. Assigns slice elements to corresponding
142 /// elements of @a a.
143 slice_array& operator=(const slice_array&);
144
145 /// Assign slice elements to corresponding elements of @a v.
146 void operator=(const valarray<_Tp>&) const;
147 /// Multiply slice elements by corresponding elements of @a v.
148 void operator*=(const valarray<_Tp>&) const;
149 /// Divide slice elements by corresponding elements of @a v.
150 void operator/=(const valarray<_Tp>&) const;
151 /// Modulo slice elements by corresponding elements of @a v.
152 void operator%=(const valarray<_Tp>&) const;
153 /// Add corresponding elements of @a v to slice elements.
154 void operator+=(const valarray<_Tp>&) const;
155 /// Subtract corresponding elements of @a v from slice elements.
156 void operator-=(const valarray<_Tp>&) const;
157 /// Logical xor slice elements with corresponding elements of @a v.
158 void operator^=(const valarray<_Tp>&) const;
159 /// Logical and slice elements with corresponding elements of @a v.
160 void operator&=(const valarray<_Tp>&) const;
161 /// Logical or slice elements with corresponding elements of @a v.
162 void operator|=(const valarray<_Tp>&) const;
163 /// Left shift slice elements by corresponding elements of @a v.
164 void operator<<=(const valarray<_Tp>&) const;
165 /// Right shift slice elements by corresponding elements of @a v.
166 void operator>>=(const valarray<_Tp>&) const;
167 /// Assign all slice elements to @a t.
168 void operator=(const _Tp &) const;
169 // ~slice_array ();
170
171 template<class _Dom>
172 void operator=(const _Expr<_Dom, _Tp>&) const;
173 template<class _Dom>
174 void operator*=(const _Expr<_Dom, _Tp>&) const;
175 template<class _Dom>
176 void operator/=(const _Expr<_Dom, _Tp>&) const;
177 template<class _Dom>
178 void operator%=(const _Expr<_Dom, _Tp>&) const;
179 template<class _Dom>
180 void operator+=(const _Expr<_Dom, _Tp>&) const;
181 template<class _Dom>
182 void operator-=(const _Expr<_Dom, _Tp>&) const;
183 template<class _Dom>
184 void operator^=(const _Expr<_Dom, _Tp>&) const;
185 template<class _Dom>
186 void operator&=(const _Expr<_Dom, _Tp>&) const;
187 template<class _Dom>
188 void operator|=(const _Expr<_Dom, _Tp>&) const;
189 template<class _Dom>
190 void operator<<=(const _Expr<_Dom, _Tp>&) const;
191 template<class _Dom>
192 void operator>>=(const _Expr<_Dom, _Tp>&) const;
193
194 private:
195 friend class valarray<_Tp>;
196 slice_array(_Array<_Tp>, const slice&);
197
198 const size_t _M_sz;
199 const size_t _M_stride;
200 const _Array<_Tp> _M_array;
201
202#if __cplusplus < 201103L
203 // not implemented
204 slice_array();
205#else
206 public:
207 slice_array() = delete;
208#endif
209 };
210
211 template<typename _Tp>
212 inline
213 slice_array<_Tp>::slice_array(_Array<_Tp> __a, const slice& __s)
214 : _M_sz(__s.size()), _M_stride(__s.stride()),
215 _M_array(__a.begin() + __s.start()) {}
216
217 template<typename _Tp>
218 inline
219 slice_array<_Tp>::slice_array(const slice_array<_Tp>& __a)
220 : _M_sz(__a._M_sz), _M_stride(__a._M_stride), _M_array(__a._M_array) {}
221
222 // template<typename _Tp>
223 // inline slice_array<_Tp>::~slice_array () {}
224
225 template<typename _Tp>
226 inline slice_array<_Tp>&
227 slice_array<_Tp>::operator=(const slice_array<_Tp>& __a)
228 {
229 std::__valarray_copy(__a._M_array, __a._M_sz, __a._M_stride,
230 _M_array, _M_stride);
231 return *this;
232 }
233
234 template<typename _Tp>
235 inline void
236 slice_array<_Tp>::operator=(const _Tp& __t) const
237 { std::__valarray_fill(_M_array, _M_sz, _M_stride, __t); }
238
239 template<typename _Tp>
240 inline void
241 slice_array<_Tp>::operator=(const valarray<_Tp>& __v) const
242 { std::__valarray_copy(_Array<_Tp>(__v), _M_array, _M_sz, _M_stride); }
243
244 template<typename _Tp>
245 template<class _Dom>
246 inline void
247 slice_array<_Tp>::operator=(const _Expr<_Dom,_Tp>& __e) const
248 { std::__valarray_copy(__e, _M_sz, _M_array, _M_stride); }
249
250 /// @cond undocumented
251#undef _DEFINE_VALARRAY_OPERATOR
252#define _DEFINE_VALARRAY_OPERATOR(_Op,_Name) \
253 template<typename _Tp> \
254 inline void \
255 slice_array<_Tp>::operator _Op##=(const valarray<_Tp>& __v) const \
256 { \
257 _Array_augmented_##_Name(_M_array, _M_sz, _M_stride, _Array<_Tp>(__v));\
258 } \
259 \
260 template<typename _Tp> \
261 template<class _Dom> \
262 inline void \
263 slice_array<_Tp>::operator _Op##=(const _Expr<_Dom,_Tp>& __e) const\
264 { \
265 _Array_augmented_##_Name(_M_array, _M_stride, __e, _M_sz); \
266 }
267
268
269_DEFINE_VALARRAY_OPERATOR(*, __multiplies)
270_DEFINE_VALARRAY_OPERATOR(/, __divides)
271_DEFINE_VALARRAY_OPERATOR(%, __modulus)
272_DEFINE_VALARRAY_OPERATOR(+, __plus)
273_DEFINE_VALARRAY_OPERATOR(-, __minus)
274_DEFINE_VALARRAY_OPERATOR(^, __bitwise_xor)
275_DEFINE_VALARRAY_OPERATOR(&, __bitwise_and)
276_DEFINE_VALARRAY_OPERATOR(|, __bitwise_or)
277_DEFINE_VALARRAY_OPERATOR(<<, __shift_left)
278_DEFINE_VALARRAY_OPERATOR(>>, __shift_right)
279
280#undef _DEFINE_VALARRAY_OPERATOR
281 /// @endcond
282
283 /// @} group numeric_arrays
284
285_GLIBCXX_END_NAMESPACE_VERSION
286} // namespace
287
288#endif /* _SLICE_ARRAY_H */
std::slice::size
size_t size() const
Return size of slice.
Definition slice_array.h:109
std::slice_array::operator=
slice_array & operator=(const slice_array &)
Assignment operator. Assigns slice elements to corresponding elements of a.
Definition slice_array.h:227
std::slice::slice
slice()
Construct an empty slice.
Definition slice_array.h:97
std::slice_array::slice_array
slice_array(const slice_array &)
Copy constructor. Both slices refer to the same underlying array.
Definition slice_array.h:219
std::slice::stride
size_t stride() const
Return array stride of slice.
Definition slice_array.h:113
std::slice::start
size_t start() const
Return array offset of first slice element.
Definition slice_array.h:105
std
ISO C++ entities toplevel namespace is std.
std::size
constexpr auto size(const _Container &__cont) noexcept(noexcept(__cont.size())) -> decltype(__cont.size())
Return the size of a container.
Definition range_access.h:294
std::begin
constexpr auto begin(_Container &__cont) noexcept(noexcept(__cont.begin())) -> decltype(__cont.begin())
Return an iterator pointing to the first element of the container.
Definition range_access.h:55
std::valarray
Smart array designed to support numeric processing.
Definition valarray:137
std::slice_array
Reference to one-dimensional subset of an array.
Definition slice_array.h:131
std::slice_array::operator|=
void operator|=(const valarray< _Tp > &) const
Logical or slice elements with corresponding elements of v.
std::slice_array::operator<<=
void operator<<=(const valarray< _Tp > &) const
Left shift slice elements by corresponding elements of v.
std::slice_array::operator^=
void operator^=(const valarray< _Tp > &) const
Logical xor slice elements with corresponding elements of v.
std::slice_array::operator*=
void operator*=(const valarray< _Tp > &) const
Multiply slice elements by corresponding elements of v.
std::slice_array::operator%=
void operator%=(const valarray< _Tp > &) const
Modulo slice elements by corresponding elements of v.
std::slice_array::operator>>=
void operator>>=(const valarray< _Tp > &) const
Right shift slice elements by corresponding elements of v.
std::slice_array::operator&=
void operator&=(const valarray< _Tp > &) const
Logical and slice elements with corresponding elements of v.
std::slice_array::operator-=
void operator-=(const valarray< _Tp > &) const
Subtract corresponding elements of v from slice elements.
std::slice_array::operator+=
void operator+=(const valarray< _Tp > &) const
Add corresponding elements of v to slice elements.
std::slice_array::operator/=
void operator/=(const valarray< _Tp > &) const
Divide slice elements by corresponding elements of v.
std::slice
Class defining one-dimensional subset of an array.
Definition slice_array.h:62
std::slice::operator==
friend bool operator==(const slice &, const slice &)=default
Equality comparison.