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

void clear();		(until C++11)
void clear() noexcept;		(since C++11) (until C++20)
constexpr void clear() noexcept;		(since C++20)

Erases all elements from the container. After this call, size() returns zero.

Invalidates any references, pointers, or iterators referring to contained elements. Any past-the-end iterators are also invalidated.

Leaves the capacity() of the vector unchanged (Note: the standard's restriction on the changes to capacity is in the specification of vector::reserve, see [1]).

Parameters

(none)

Return value

(none)

Complexity

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

Example

#include <iostream>
#include <string_view>
#include <vector>
 
void print_info(std::string_view rem, const std::vector<int>& v)
{
    std::cout << rem << "{ ";
    for (const auto& value : v)
        std::cout << value << ' ';
    std::cout << "}\n";
    std::cout << "Size=" << v.size() << ", Capacity=" << v.capacity() << '\n';
}
 
int main()
{
    std::vector<int> container{1, 2, 3};
    print_info("Before clear: ", container);
    container.clear();
    print_info("After clear: ", container);
}

Output:

Before clear: { 1 2 3 }
Size=3, Capacity=3
After clear: { }
Size=0, Capacity=3

Defect reports

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