std::indirect_array - cppreference.com (original) (raw)

| | | | | ------------------------------------------- | | | | 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.

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[edit] Member functions

[edit] Example

#include #include   int main() { std::valarray 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   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