std::indirect_array
From cppreference.com
| Defined in header <valarray>
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template< class T > class indirect_array; |
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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
constructs a indirect_array (public member function) | |
destroys a indirect_array (public member function) | |
| assigns contents (public member function) | |
| performs arithmetic operation on the array referred by indirect array. (public member function) |
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