std::valarray<T>::operator= (3) - Linux Manuals

std::valarray<T>::operator=: std::valarray<T>::operator=

NAME

std::valarray<T>::operator= - std::valarray<T>::operator=

Synopsis

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) (none)
3-8) (none)

Example

// Run this code

  #include <valarray>
  #include <iostream>

  int main()
  {
      std::valarray<int> v1(3);
      v1 = -1; // from a scalar
      std::cout << "assigned from scalar: ";
      for(int n: v1) std::cout << n << ' '; std::cout << '\n';

      v1 = {1, 2, 3, 4, 5, 6}; // from initializer list of different size
      std::cout << "assigned from initializer_list: ";
      for(int n: v1) std::cout << n << ' '; std::cout << '\n';

      std::valarray<int> v2(3);
      v2 = v1[std::slice(0,3,2)]; // from slice array
      std::cout << "every 2nd element starting at pos 0: ";
      for(int n: v2) std::cout << n << ' '; std::cout << '\n';

      v2 = v1[v1 % 2 == 0]; // from mask array
      std::cout << "values that are even : ";
      for(int n: v2) std::cout << n << ' '; std::cout << '\n';

      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]; // from indirect array
      std::cout << "values at positions 0,1,2,4: ";
      for(int n: v2) std::cout << n << ' '; std::cout << '\n';
  }

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