C++

参考

<vector>

vector

public member function
<vector>

std::vector::operator=

copy (1)
 vector& operator= (const vector& x);
copy (1)
vector& operator= (const vector& x);
move (2)
vector& operator= (vector&& x);
initializer list (3)
vector& operator= (initializer_list<value_type> il);
Assign content
Assigns new contents to the container, replacing its current contents, and modifying its size accordingly.

Copies all the elements from x into the container.

The container preserves its current allocator, which is used to allocate storage in case of reallocation.
The copy assignment (1) copies all the elements from x into the container (with x preserving its contents).

The move assignment (2) moves the elements of x into the container (x is left in an unspecified but valid state).

The initializer list assignment (3) copies the elements of il into the container.

The container preserves its current allocator, except if the allocator traits indicate that x's allocator should propagate. This allocator is used (through its traits) to allocate and deallocate storage if a reallocation happens, and to construct or destroy elements, if needed.

Any elements held in the container before the call are either assigned to or destroyed.

参数

x
A vector object of the same type (i.e., with the same template parameters,T和Alloc).
il
一个 initializer_list 对象。编译器将自动从初始化列表声明器创建此类对象。
成员类型value_typeis the type of the elements in the container, defined in vector as an alias of its first template parameter (T).

返回值

*this

示例

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// vector assignment
#include <iostream>
#include <vector>

int main ()
{
  std::vector<int> foo (3,0);
  std::vector<int> bar (5,0);

  bar = foo;
  foo = std::vector<int>();

  std::cout << "Size of foo: " << int(foo.size()) << '\n';
  std::cout << "Size of bar: " << int(bar.size()) << '\n';
  return 0;
}

输出
Size of foo: 0
Size of bar: 3


复杂度

Linear in size.

迭代器有效性

All iterators, references and pointers related to this container before the call are invalidated.

In the move assignment, iterators, pointers and references referring to elements in x are also invalidated.

数据竞争

All copied elements are accessed.
The move assignment (2) modifies x.
The container and all its elements are modified.

异常安全

Basic guarantee: if an exception is thrown, the container is in a valid state.
If allocator_traits::construct is not supported with the appropriate arguments for the element constructions, or ifvalue_typeis not copy assignable (or move assignable for (2)), it causes undefined behavior.

另见

vector::assign
Assign vector content (public member function)