std::forward_list<T,Allocator>::clear

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C++
 
Containers library
Sequence
(C++11)
(C++11)
Associative
Unordered associative
(C++11)
(C++11)
(C++11)
(C++11)
Adaptors
Views
(C++20)
 
std::forward_list
Member functions
Element access
Iterators
Capacity
Modifiers
forward_list::clear
Operations
Non-member functions
(C++20)(C++20)
(until C++20)(until C++20)(until C++20)(until C++20)(until C++20)(C++20)
Deduction guides(C++17)
 
void clear() noexcept;
 (since C++11)

Erases all elements from the container.

Invalidates any references, pointers, or iterators referring to contained elements. Any past-the-end iterator remains valid.

Parameters

(none)

Return value

(none)

Complexity

Linear in the size of the container, i.e., the number of elements.

Example

Run this code
#include <algorithm>
#include <iostream>
#include <forward_list>
 
int main()
{
    std::forward_list<int> container{1, 2, 3};
 
    auto print = [](const int& n) { std::cout << " " << n; };
 
    std::cout << "Before clear:";
    std::for_each(container.begin(), container.end(), print);
    std::cout << '\n';
 
    std::cout << "Clear\n";
    container.clear();
 
    std::cout << "After clear:";
    std::for_each(container.begin(), container.end(), print);
    std::cout << '\n';
}

Output: 

Before clear: 1 2 3
Clear
After clear:

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR Applied to Behavior as published Correct behavior
LWG 2231 C++11 complexity guarantee was mistakenly omitted in C++11 complexity reaffirmed as linear


See also

(C++11)
 erases an element after an element
(public member function)
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