std::indirect_array

Defined in header <valarray>

1	`template<` `class` `T >` `class` `indirect_array;`

std::gslice_array is a helper template used by std::indirect_array subscript operator. It has reference semantics to a subset of the array specified by an indirect array (std::valarray<std::size_t> object).

Member types

Type	Definition
`value_type`	`T`

Member functions

(constructor)	constructs a `indirect_array` (public member function)
(destructor)	destroys a `indirect_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 indirect array. (public member function)

Example

#include <iostream>
#include <valarray>
  
int main()
{
    std::valarray<int> data = {0,1,2,3,4,5,6,7,8,9};
  
    std::valarray<std::size_t> idx = {0,2,4,6,8};
  
    std::cout << "Original valarray: ";
    for(int n: data) std::cout << n << ' ';
    std::cout << '\n';
  
    data[idx] += data[idx]; // double the values at indexes 'idx'
  
    // the type of data[idx] is std::indirect_array<int>
  
    std::cout << "After indirect modification: ";
    for(int n: data) std::cout << n << ' ';
    std::cout << '\n';
}

Output:

Original valarray: 0 1 2 3 4 5 6 7 8 9 
After indirect modification: 0 1 4 3 8 5 12 7 16 9

Links:

http://en.cppreference.com/w/cpp/numeric/valarray/indirect_array

doc_CPP

2025-01-10 15:47:30

Comments