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

 

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std::vector

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vector::vector vector::~vector vector::operator= vector::assign vector::assign_range (C++23)   vector::get_allocator Element access vector::operator[] vector::at vector::data vector::front vector::back Iterators vector::beginvector::cbegin (C++11) vector::endvector::cend (C++11) vector::rbeginvector::crbegin (C++11) vector::rendvector::crend (C++11)	Capacity vector::empty vector::size vector::max_size vector::reserve vector::capacity vector::shrink_to_fit (DR*) Modifiers vector::clear vector::erase vector::insert vector::insert_range (C++23) vector::append_range (C++23) vector::emplace (C++11) vector::emplace_back (C++11) vector::push_back vector::pop_back vector::resize vector::swap
Non-member functions
operator==operator<=> (C++20) swap(std::vector) erase(std::vector)erase_if(std::vector) (C++20)(C++20)	operator!=operator<operator>operator<=operator>= (until C++20)(until C++20)(until C++20)(until C++20)(until C++20)
Deduction guides(C++17)

 

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

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

Invalidates any references, pointers, and 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 reserve(), see SO).

Parameters

(none)

Return value

(none)

Complexity

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

Example

Run this code

#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.

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

erase

erases elements (public member function)