slice_array.h
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// The template and inlines for the -*- C++ -*- slice_array class.
// Copyright (C) 1997-2025 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library. This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 3, or (at your option)
// any later version.
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.
// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
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/** @file bits/slice_array.h
* This is an internal header file, included by other library headers.
* Do not attempt to use it directly. @headername{valarray}
*/
// Written by Gabriel Dos Reis <Gabriel.Dos-Reis@DPTMaths.ENS-Cachan.Fr>
#ifndef _SLICE_ARRAY_H
#define _SLICE_ARRAY_H 1
#ifdef _GLIBCXX_SYSHDR
#pragma GCC system_header
#endif
namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION
/**
* @addtogroup numeric_arrays
* @{
*/
/**
* @brief Class defining one-dimensional subset of an array.
*
* The slice class represents a one-dimensional subset of an array,
* specified by three parameters: start offset, size, and stride. The
* start offset is the index of the first element of the array that is part
* of the subset. The size is the total number of elements in the subset.
* Stride is the distance between each successive array element to include
* in the subset.
*
* For example, with an array of size 10, and a slice with offset 1, size 3
* and stride 2, the subset consists of array elements 1, 3, and 5.
*/
class slice
{
public:
/// Construct an empty slice.
slice();
/**
* @brief Construct a slice.
*
* @param __o Offset in array of first element.
* @param __d Number of elements in slice.
* @param __s Stride between array elements.
*/
slice(size_t __o, size_t __d, size_t __s);
/// Return array offset of first slice element.
size_t start() const;
/// Return size of slice.
size_t size() const;
/// Return array stride of slice.
size_t stride() const;
#if __cpp_impl_three_way_comparison >= 201907L
/// Equality comparison
friend bool operator==(const slice&, const slice&) = default;
#endif
private:
size_t _M_off; // offset
size_t _M_sz; // size
size_t _M_st; // stride unit
};
// _GLIBCXX_RESOLVE_LIB_DEFECTS
// 543. valarray slice default constructor
inline
slice::slice()
: _M_off(0), _M_sz(0), _M_st(0) {}
inline
slice::slice(size_t __o, size_t __d, size_t __s)
: _M_off(__o), _M_sz(__d), _M_st(__s) {}
inline size_t
slice::start() const
{ return _M_off; }
inline size_t
slice::size() const
{ return _M_sz; }
inline size_t
slice::stride() const
{ return _M_st; }
/**
* @brief Reference to one-dimensional subset of an array.
*
* A slice_array is a reference to the actual elements of an array
* specified by a slice. The way to get a slice_array is to call
* operator[](slice) on a valarray. The returned slice_array then permits
* carrying operations out on the referenced subset of elements in the
* original valarray. For example, operator+=(valarray) will add values
* to the subset of elements in the underlying valarray this slice_array
* refers to.
*
* @param Tp Element type.
*/
template<typename _Tp>
class slice_array
{
public:
typedef _Tp value_type;
// _GLIBCXX_RESOLVE_LIB_DEFECTS
// 253. valarray helper functions are almost entirely useless
/// Copy constructor. Both slices refer to the same underlying array.
slice_array(const slice_array&);
/// Assignment operator. Assigns slice elements to corresponding
/// elements of @a a.
slice_array& operator=(const slice_array&);
/// Assign slice elements to corresponding elements of @a v.
void operator=(const valarray<_Tp>&) const;
/// Multiply slice elements by corresponding elements of @a v.
void operator*=(const valarray<_Tp>&) const;
/// Divide slice elements by corresponding elements of @a v.
void operator/=(const valarray<_Tp>&) const;
/// Modulo slice elements by corresponding elements of @a v.
void operator%=(const valarray<_Tp>&) const;
/// Add corresponding elements of @a v to slice elements.
void operator+=(const valarray<_Tp>&) const;
/// Subtract corresponding elements of @a v from slice elements.
void operator-=(const valarray<_Tp>&) const;
/// Logical xor slice elements with corresponding elements of @a v.
void operator^=(const valarray<_Tp>&) const;
/// Logical and slice elements with corresponding elements of @a v.
void operator&=(const valarray<_Tp>&) const;
/// Logical or slice elements with corresponding elements of @a v.
void operator|=(const valarray<_Tp>&) const;
/// Left shift slice elements by corresponding elements of @a v.
void operator<<=(const valarray<_Tp>&) const;
/// Right shift slice elements by corresponding elements of @a v.
void operator>>=(const valarray<_Tp>&) const;
/// Assign all slice elements to @a t.
void operator=(const _Tp &) const;
// ~slice_array ();
template<class _Dom>
void operator=(const _Expr<_Dom, _Tp>&) const;
template<class _Dom>
void operator*=(const _Expr<_Dom, _Tp>&) const;
template<class _Dom>
void operator/=(const _Expr<_Dom, _Tp>&) const;
template<class _Dom>
void operator%=(const _Expr<_Dom, _Tp>&) const;
template<class _Dom>
void operator+=(const _Expr<_Dom, _Tp>&) const;
template<class _Dom>
void operator-=(const _Expr<_Dom, _Tp>&) const;
template<class _Dom>
void operator^=(const _Expr<_Dom, _Tp>&) const;
template<class _Dom>
void operator&=(const _Expr<_Dom, _Tp>&) const;
template<class _Dom>
void operator|=(const _Expr<_Dom, _Tp>&) const;
template<class _Dom>
void operator<<=(const _Expr<_Dom, _Tp>&) const;
template<class _Dom>
void operator>>=(const _Expr<_Dom, _Tp>&) const;
private:
friend class valarray<_Tp>;
slice_array(_Array<_Tp>, const slice&);
const size_t _M_sz;
const size_t _M_stride;
const _Array<_Tp> _M_array;
#if __cplusplus < 201103L
// not implemented
slice_array();
#else
public:
slice_array() = delete;
#endif
};
template<typename _Tp>
inline
slice_array<_Tp>::slice_array(_Array<_Tp> __a, const slice& __s)
: _M_sz(__s.size()), _M_stride(__s.stride()),
_M_array(__a.begin() + __s.start()) {}
template<typename _Tp>
inline
slice_array<_Tp>::slice_array(const slice_array<_Tp>& __a)
: _M_sz(__a._M_sz), _M_stride(__a._M_stride), _M_array(__a._M_array) {}
// template<typename _Tp>
// inline slice_array<_Tp>::~slice_array () {}
template<typename _Tp>
inline slice_array<_Tp>&
slice_array<_Tp>::operator=(const slice_array<_Tp>& __a)
{
std::__valarray_copy(__a._M_array, __a._M_sz, __a._M_stride,
_M_array, _M_stride);
return *this;
}
template<typename _Tp>
inline void
slice_array<_Tp>::operator=(const _Tp& __t) const
{ std::__valarray_fill(_M_array, _M_sz, _M_stride, __t); }
template<typename _Tp>
inline void
slice_array<_Tp>::operator=(const valarray<_Tp>& __v) const
{ std::__valarray_copy(_Array<_Tp>(__v), _M_array, _M_sz, _M_stride); }
template<typename _Tp>
template<class _Dom>
inline void
slice_array<_Tp>::operator=(const _Expr<_Dom,_Tp>& __e) const
{ std::__valarray_copy(__e, _M_sz, _M_array, _M_stride); }
/// @cond undocumented
#undef _DEFINE_VALARRAY_OPERATOR
#define _DEFINE_VALARRAY_OPERATOR(_Op,_Name) \
template<typename _Tp> \
inline void \
slice_array<_Tp>::operator _Op##=(const valarray<_Tp>& __v) const \
{ \
_Array_augmented_##_Name(_M_array, _M_sz, _M_stride, _Array<_Tp>(__v));\
} \
\
template<typename _Tp> \
template<class _Dom> \
inline void \
slice_array<_Tp>::operator _Op##=(const _Expr<_Dom,_Tp>& __e) const\
{ \
_Array_augmented_##_Name(_M_array, _M_stride, __e, _M_sz); \
}
_DEFINE_VALARRAY_OPERATOR(*, __multiplies)
_DEFINE_VALARRAY_OPERATOR(/, __divides)
_DEFINE_VALARRAY_OPERATOR(%, __modulus)
_DEFINE_VALARRAY_OPERATOR(+, __plus)
_DEFINE_VALARRAY_OPERATOR(-, __minus)
_DEFINE_VALARRAY_OPERATOR(^, __bitwise_xor)
_DEFINE_VALARRAY_OPERATOR(&, __bitwise_and)
_DEFINE_VALARRAY_OPERATOR(|, __bitwise_or)
_DEFINE_VALARRAY_OPERATOR(<<, __shift_left)
_DEFINE_VALARRAY_OPERATOR(>>, __shift_right)
#undef _DEFINE_VALARRAY_OPERATOR
/// @endcond
/// @} group numeric_arrays
_GLIBCXX_END_NAMESPACE_VERSION
} // namespace
#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::begin
_Tp * begin(valarray< _Tp > &__va) noexcept
Return an iterator pointing to the first element of the valarray.
Definition valarray:1229
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:274
std::valarray
Smart array designed to support numeric processing.
Definition valarray:132
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.