std::gslice_array

 

C++

Compiler support

Freestanding and hosted

Language

Standard library

Standard library headers

Named requirements

Feature test macros(C++20)

Language support library

Concepts library(C++20)

Diagnostics library

Memory management library

Metaprogramming library(C++11)

General utilities library

Containers library

Iterators library

Ranges library(C++20)

Algorithms library

Strings library

Text processing library

Numerics library

Date and time library

Input/output library

Filesystem library(C++17)

Concurrency support library(C++11)

Execution control library(C++26)

Technical specifications

Symbols index

External libraries

 

Numerics library

Common mathematical functions
Mathematical special functions(C++17)
Mathematical constants(C++20)
Basic linear algebra algorithms(C++26)
Data-parallel types (SIMD)(C++26)
Floating-point environment(C++11)
Complex numbers
Numeric array (valarray)
Pseudo-random number generation
Bit manipulation(C++20)
Saturation arithmetic(C++26)
Factor operations
gcd (C++17)	lcm (C++17)
Interpolations
midpoint (C++20)	lerp (C++20)
Generic numeric operations
iota (C++11) ranges::iota (C++23) accumulate inner_product adjacent_difference    partial_sum	reduce (C++17) transform_reduce (C++17) inclusive_scan (C++17) exclusive_scan (C++17) transform_inclusive_scan (C++17) transform_exclusive_scan (C++17)
C-style checked integer arithmetic
ckd_add (C++26) ckd_sub (C++26)	ckd_mul (C++26)

 

std::valarray

Member functions
valarray::valarray valarray::~valarray valarray::operator= valarray::operator[] valarray::swap valarray::size valarray::resize valarray::sum valarray::min valarray::max valarray::shift valarray::cshift valarray::apply	valarray::operator+valarray::operator-valarray::operator~valarray::operator! valarray::operator+=valarray::operator-=valarray::operator*=valarray::operator/=valarray::operator%=valarray::operator&=valarray::operator|=valarray::operator^=valarray::operator<<=valarray::operator>>=
Non-member functions
swap(std::valarray) (C++11) begin(std::valarray) (C++11)   end(std::valarray) (C++11) abs exp log log10 pow sqrt sin cos tan asin acos atan atan2 sinh cosh tanh	operator*operator/operator%operator+operator-operator^operator&operator|operator<<operator>>operator&&operator|| operator==operator!=operator<operator>operator<=operator>=
Helper classes
slice_array gslice_array indirect_array	slice gslice mask_array
Deduction guides(C++17)

 

std::gslice_array

Member functions

gslice_array::gslice_array

gslice_array::~gslice_array

gslice_array::operator=

gslice_array::operator+=gslice_array::operator-=gslice_array::operator*=gslice_array::operator/=gslice_array::operator%=gslice_array::operator&=gslice_array::operator|=gslice_array::operator^=gslice_array::operator<<=gslice_array::operator>>=

 

Defined in header <valarray>
template<class T > class gslice_array;

std::gslice_array is a helper template used by the valarray subscript operator with std::gslice argument. It has reference semantics to a subset of the array specified by the std::gslice object.

Member types

Type	Definition
value_type	T

Member functions

(constructor)	constructs a gslice_array (public member function)
(destructor)	destroys a gslice_array (public member function)
operator=	assigns contents (public member function)
operator+=operator-=operator*=operator/=operator%=operator&=operator|=operator^=operator<<=operator>>=	performs arithmetic operation on the array referred by generic slice. (public member function)

Example

Run this code

#include <cassert>#include <cstddef>#include <iomanip>#include <iostream>#include <numeric>#include <valarray>   int main(){std::valarray<int> data(32);std::iota(std::begin(data), std::end(data), 0);   conststd::size_t offset =1, z =2, y =3, x =4;conststd::valarray<std::size_t> sizes{z, y, x};conststd::valarray<std::size_t> strides{15, 5, 1};conststd::gslice gslice =std::gslice(offset, sizes, strides);// Indices are generated according to the formula:// index[k] = offset + [0,1,2)*15 + [0,1,2,3)*5 + [0,1,2,3,4)*1// = offset + inner_product(sizes[k], strides);// where sizes[k] = {[0,z), [0,y), [0,x)}, while the rightmost index (x)// runs fastest. As a result we have following set of indices:// index[0] = 1 + 0*15 + 0*5 + 0*1 = 1// index[1] = 1 + 0*15 + 0*5 + 1*1 = 2// index[2] = 1 + 0*15 + 0*5 + 2*1 = 3// index[3] = 1 + 0*15 + 0*5 + 3*1 = 4// index[4] = 1 + 0*15 + 1*5 + 0*1 = 6// index[5] = 1 + 0*15 + 1*5 + 1*1 = 7// index[6] = 1 + 0*15 + 1*5 + 2*1 = 8// index[7] = 1 + 0*15 + 1*5 + 3*1 = 9// ...// index[22] = 1 + 1*15 + 2*5 + 2*1 = 28// index[23] = 1 + 1*15 + 2*5 + 3*1 = 29   conststd::valarray<int> indices = data[gslice];for(unsigned i =0; i != indices.size();++i)std::cout<<std::setfill('0')<<std::setw(2)<< indices[i]<<' ';std::cout<<"\nTotal indices: "<< indices.size()<<'\n';assert(indices.size()== x * y * z);   data =0; std::gslice_array<int> gslice_array = data[gslice]; gslice_array =1;// Cells that correspond to generated indices = '1', skipped cells = '0'.for(auto i : data)std::cout<< i <<' ';std::cout<<"\nSum of ones = "<< data.sum()<<'\n';}

Output:

01 02 03 04 06 07 08 09 11 12 13 14 16 17 18 19 21 22 23 24 26 27 28 29 Total indices: 24 0 1 1 1 1 0 1 1 1 1 0 1 1 1 1 0 1 1 1 1 0 1 1 1 1 0 1 1 1 1 0 0 Sum of ones = 24

See also

slice_array	proxy to a subset of a valarray after applying a slice (class template)
mdspan (C++23)	a multi-dimensional non-owning array view (class template)