std:: mask_array

std::mask_array is a helper template used by the valarray subscript operator with std:: valarray < bool > argument. It has reference semantics and provides access to the subset of the valarray consisting of the elements whose indices correspond to true values in the std:: valarray < bool > mask.

Member types

Member functions

Example

#include <iostream>
#include <valarray>
 
void println(auto rem, const auto& data)
{
    for (std::cout << rem; int n : data)
        std::cout << n << ' ';
    std::cout << '\n';
}
 
int main()
{
    std::valarray<int> data{0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
 
    println("Initial valarray: ", data);
 
    data[data > 5] = -1;
    // the type of data>5 is std::valarray<bool>
    // the type of data[data>5] is std::mask_array<int>
 
    println("After v[v>5]=-1:  ", data);
}

Initial valarray: 0 1 2 3 4 5 6 7 8 9
After v[v>5]=-1:  0 1 2 3 4 5 -1 -1 -1 -1

See also