C++

参考

<list>

list

public member function
<list>

std::list::operator=

copy (1)
 list& operator= (const list& x);
copy (1)
list& operator= (const list& x);
move (2)
list& operator= (list&& x);
initializer list (3)
list& 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 additional storage if needed.
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 x's allocator should propagate.
This allocator is used (through its traits) to allocate or deallocate if there are changes in storage requirements, 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
一个 list 对象，具有相同的类型（即相同的模板参数，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 list as an alias of its first template parameter (T).

返回值

*this

示例

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// assignment operator with lists
#include <iostream>
#include <list>

int main ()
{
  std::list<int> first (3);      // list of 3 zero-initialized ints
  std::list<int> second (5);     // list of 5 zero-initialized ints

  second = first;
  first = std::list<int>();

  std::cout << "Size of first: " << int (first.size()) << '\n';
  std::cout << "Size of second: " << int (second.size()) << '\n';
  return 0;
}
Both list containers ofintelements are initialized to sequences with different sizes. Then,secondis assigned tofirst, so both are now equal and with a size of3. And then,firstis assigned to a newly constructed empty container object, so its size is finally 0. Output
Size of first: 0
Size of second: 3


复杂度

Linear in size.

迭代器有效性

All iterators, references and pointers related to this container are invalidated, except the end iterators.

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

list::list
构造列表 (公开成员函数)
list::assign
给容器赋新值 (公开成员函数)