C++

參考

<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.

引數

x
一個 list 物件，具有相同的型別（即相同的模板引數，T和Alloc).
il
一個 initializer_list 物件。編譯器將自動從初始化列表宣告器建立此類物件。
成員型別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


複雜度

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.

資料競爭

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

異常安全

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.

另見

list::list
構造列表 (公開成員函式)
list::assign
給容器賦新值 (公開成員函式)