std::valarray::operator=
From cppreference.com
valarray<T>& operator=( const valarray<T>& other );
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(1) | |
valarray<T>& operator=( valarray<T>&& other );
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(2) | (since C++11) |
valarray<T>& operator=( const T& val );
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(3) | |
valarray<T>& operator=( const std::slice_array<T>& other);
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(4) | |
valarray<T>& operator=( const std::gslice_array<T>& other);
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(5) | |
valarray<T>& operator=( const std::mask_array<T>& other );
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(6) | |
valarray<T>& operator=( const std::indirect_array<T>& other );
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(7) | |
valarray<T>& operator=( std::initializer_list<T> il );
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(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).
Contents |
[edit] Parameters
other | - | another numeric array (or a mask) to assign |
val | - | the value to initialize each element with |
il | - | initializer list to assign |
[edit] Return value
*this
[edit] Exceptions
1) (none)
2)
noexcept specification:
noexcept
3-8) (none)
[edit] 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