NAME¶

std::indirect_array - std::indirect_array

Synopsis¶

Defined in header <valarray>
template< class T > class 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¶

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%= performs arithmetic operation on the array referred by indirect array.
operator&= (public member function)
operator|=
operator^=
operator<<=
operator>>=

Example¶

// Run this code

#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';
}

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