std::valarray::operator= - cppreference.com (original) (raw)

Replaces the contents of the numeric array.

1. Copy assignment operator. If size() != other.size(), first resizes *this as if by resize(other.size()). Each element of *this is assigned the value of the corresponding element of other.

2. Move assignment operator. Replaces the contents of *this with those of other. The value of other is unspecified after this operation. The complexity of this operation may be linear if T has non-trivial destructors, but is usually constant otherwise.

3. Replaces each value in *this with a copy of val.

4-7) Replaces the contents of *this with the result of a generalized subscripting operation. The behavior is undefined if size() does not equal the length of other or if any value on the left depends on the value on the right (e.g. v = v[v > 2]).

1. Assigns the contents of initializer list il. Equivalent to *this = valarray(il).

[edit] Parameters

[edit] Return value

*this

[edit] Exceptions

1,3-8) May throw implementation-defined exceptions.

[edit] Example

#include #include #include   void print(const char* rem, const std::valarray& v) { std::cout << std::left << std::setw(36) << rem << std::right; for (int n : v) std::cout << std::setw(3) << n; std::cout << '\n'; }   int main() { std::valarray v1(3); v1 = -1; // (3) from a scalar print("assigned from scalar: ", v1);   v1 = {1, 2, 3, 4, 5, 6}; // (8): from initializer list of different size print("assigned from initializer_list:", v1);   std::valarray v2(3); v2 = v1[std::slice(0, 3, 2)]; // (4): from slice array print("every 2nd element starting at pos 0:", v2);   v2 = v1[v1 % 2 == 0]; // (6): from mask array print("values that are even:", v2);   std::valarray<std::size_t> idx = {0, 1, 2, 4}; // index array v2.resize(4); // sizes must match when assigning from gen subscript v2 = v1[idx]; // (7): from indirect array print("values at positions 0, 1, 2, 4:", v2); }

Output:

assigned from scalar: -1 -1 -1 assigned from initializer_list: 1 2 3 4 5 6 every 2nd element starting at pos 0: 1 3 5 values that are even: 2 4 6 values at positions 0, 1, 2, 4: 1 2 3 5

[edit] Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.