std::mask_array
From cppreference.com
Defined in header
<valarray>
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template< class T > class mask_array;
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std::gslice_array
is a helper template used by std::mask_array subscript operator. It has reference semantics to a subset of the array specified by an mask array (std::valarray<bool> object).
[edit] Member types
Type | Definition |
value_type
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T
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[edit] Member functions
constructs a mask_array (public member function) |
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destroys a mask_array (public member function) |
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assigns contents (public member function) |
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performs arithmetic operation on the array referred by mask. (public member function) |
[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::cout << "Initial valarray: "; for(int n: data) std::cout << n << ' '; std::cout << '\n'; data[data > 5] = -1; // the type of data>5 is std::valarray<bool> // the type of data[data>5] is std::mask_array<int> std::cout << "After v[v>5]=-1: "; for(int n: data) std::cout << n << ' '; std::cout << '\n'; }
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