public member function
<list>
std::list::assign
| range (1) | template <class InputIterator> void assign (InputIterator first, InputIterator last); |
|---|
| fill (2) | void assign (size_type n, const value_type& val); |
|---|
| range (1) | template <class InputIterator> void assign (InputIterator first, InputIterator last); |
|---|
| fill (2) | void assign (size_type n, const value_type& val); |
|---|
| initializer list (3) | void assign (initializer_list<value_type> il); |
|---|
Assign new content to container
Assigns new contents to the list container, replacing its current contents, and modifying its size accordingly.
In the
range version (1), the new contents are elements constructed from each of the elements in the range between
first and
last, in the same order.
In the
fill version (2), the new contents are
n elements, each initialized to a copy of
val.
Any storage needed for the assigned elements is allocated using the
internal allocator.
Any elements held in the container before the call are
destroyed and replaced by newly constructed elements (no assignments of elements take place).
In the
range version (1), the new contents are elements constructed from each of the elements in the range between
first and
last, in the same order.
In the
fill version (2), the new contents are
n elements, each initialized to a copy of
val.
In the
initializer list version (3), the new contents are copies of the values passed as initializer list, in the same order.
If there are changes in storage, the
internal allocator is used (through its
traits). It is also used to
destroy all existing elements, and to
construct the new ones.
Any elements held in the container before the call are either
assigned to or
destroyed.
参数
- first, last
- Input iterators to the initial and final positions in a sequence. The range used is[first,last)，它包括first和last之间的所有元素，包括first指向的元素，但不包括last指向的元素。
函数模板参数InputIteratorshall be an input iterator type that points to elements of a type from whichvalue_type对象的类型的元素。
- n
- New size for the container.
成员类型size_type是一种无符号整型类型。
- val
- Value to fill the container with. Each of the n elements in the container will be initialized to a copy of this value.
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).
- 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).
示例
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
|
// list::assign
#include <iostream>
#include <list>
int main ()
{
std::list<int> first;
std::list<int> second;
first.assign (7,100); // 7 ints with value 100
second.assign (first.begin(),first.end()); // a copy of first
int myints[]={1776,7,4};
first.assign (myints,myints+3); // assigning from array
std::cout << "Size of first: " << int (first.size()) << '\n';
std::cout << "Size of second: " << int (second.size()) << '\n';
return 0;
}
|
Size of first: 3
Size of second: 7
|
复杂度
Linear in initial and final sizes (destructions, constructions).
迭代器有效性
All iterators, references and pointers related to this container are invalidated, except the end iterators.
数据竞争
All copied elements are accessed.
The container is modified.
所有包含的元素都被修改。
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 if the range specified by[first,last)无效，则会导致未定义行为。