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std::mask_array

From cppreference.com
< cpp‎ | numeric‎ | valarray
 
 
 
 
 
Defined in header <valarray>
template< class T > class 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.

Contents

[edit] Member types

Type Definition
value_type T

[edit] Member functions

constructs a mask_array
(public member function) [edit]
destroys a mask_array
(public member function) [edit]
assigns contents
(public member function) [edit]
performs arithmetic operation on the array referred by mask.
(public member function) [edit]

[edit] 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);
}

Output:

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

[edit] See also

(parallelism TS v2)
data-parallel type with the element type bool
(class template) [edit]