std::valarray<T>::operator=

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< cpp‎ | numeric‎ | valarray
 
 
 
 
valarray<T>& operator=( const valarray<T>& other );
(1)
valarray<T>& operator=( valarray<T>&& other ) noexcept;
(2) (since C++11)
valarray<T>& operator=( const T& val );
(3)
valarray<T>& operator=( const std::slice_array<T>& other);
(4)
valarray<T>& operator=( const std::gslice_array<T>& other);
(5)
valarray<T>& operator=( const std::mask_array<T>& other );
(6)
valarray<T>& operator=( const std::indirect_array<T>& other );
(7)
valarray<T>& operator=( std::initializer_list<T> il );
(8) (since C++11)

Replaces the contents of the numeric array.

1) Copy assignment operator. Each element of *this is assigned the value of the corresponding element of other. If the length of other does not equal the length of *this, the behavior is undefined (until C++11) first resizes as if by resize(other.size()) (since C++11).
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 the length of the argument does not equal the length of *this or if any value on the left depends on the value on the right (e.g v=v[v>2]).
8) Assigns the contents of initializer list il. Equivalent to *this = valarray(il).

Parameters

other - another numeric array (or a mask) to assign
val - the value to initialize each element with
il - initializer list to assign

Return value

*this

Exceptions

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

Example

#include <iomanip>
#include <iostream>
#include <valarray>
 
void print(const char* rem, const std::valarray<int>& 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<int> 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<int> 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