std::forward_list<T,Allocator>::clear
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forward_list::clear
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void clear() noexcept;
(since C++11) (constexpr since C++26)
Erases all elements from the container.
Invalidates any references, pointers, and iterators referring to contained elements. Any past-the-end iterator remains valid.
Contents
[edit] Complexity
Linear in the size of the container, i.e., the number of elements.
[edit] Example
Run this code
#include <iostream> #include <string_view> #include <forward_list> void print_info(std::string_view rem, const std::forward_list <int>& v) { std::cout << rem << "{ "; for (const auto& value : v) std::cout << value << ' '; std::cout << "}\n"; } int main() { std::forward_list <int> container{1, 2, 3}; print_info("Before clear: ", container); container.clear(); print_info("After clear: ", container); }
Output:
Before clear: { 1 2 3 }
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 |