std::indirect_array
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std::valarray
std::indirect_array
Member functions
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.
[edit] Member types
Type
Definition
value_type
T
[edit] Member functions
performs arithmetic operation on the array referred by indirect array.
(public member function) [edit]
(public member function) [edit]
[edit] 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