std:: indirect_array

std::indirect_array is a helper template used by the valarray subscript operator with std:: valarray < std:: size_t > argument. It has reference semantics to a subset of the array whose indices specified by the std:: valarray < std:: size_t > object.

Member types

Member functions

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 indices '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';
}

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