std::list<T,Allocator>::empty

 

C++

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Named requirements

Feature test macros (C++20)

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Concepts library (C++20)

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Diagnostics library

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Containers library

Iterators library

Ranges library (C++20)

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Technical specifications

Symbols index

External libraries

 

Containers library

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array (C++11)

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list

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Adaptors

stack

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std::list

Member functions

list::list

list::~list

list::operator=

list::assign

list::assign_range (C++23)

list::get_allocator

Element access

list::front

list::back

Iterators

list::beginlist::cbegin (C++11)

list::endlist::cend (C++11)

list::rbeginlist::crbegin (C++11)

list::rendlist::crend (C++11)

Capacity

list::empty

list::size

list::max_size

Modifiers

list::clear

list::insert

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list::emplace (C++11)

list::erase

list::push_front

list::emplace_front (C++11)

list::prepend_range (C++23)

list::pop_front

list::push_back

list::emplace_back (C++11)

list::append_range (C++23)

list::pop_back

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list::swap

Operations

list::merge

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list::removelist::remove_if

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Non-member functions

std::swap

eraseerase_if (C++20)(C++20)

operator==operator!=operator<operator>operator<=operator>=operator<=> (until C++20)(until C++20)(until C++20)(until C++20)(until C++20)(C++20)

Deduction guides(C++17)

 

bool empty() const;		(until C++11)
bool empty() const noexcept;		(since C++11) (until C++20)
[[nodiscard]] bool empty() const noexcept;		(since C++20)

Checks if the container has no elements, i.e. whether begin() == end().

Parameters

(none)

Return value

true if the container is empty, false otherwise

Complexity

Constant.

Example

The following code uses empty to check if a std::list<int> contains any elements:

Run this code

#include <list>
#include <iostream>
 
int main()
{
    std::list<int> numbers;
    std::cout << std::boolalpha;
    std::cout << "Initially, numbers.empty(): " << numbers.empty() << '\n';
 
    numbers.push_back(42);
    numbers.push_back(13317); 
    std::cout << "After adding elements, numbers.empty(): " << numbers.empty() << '\n';
}

Output:

Initially, numbers.empty(): true
After adding elements, numbers.empty(): false

See also

size	returns the number of elements (public member function)
empty (C++17)	checks whether the container is empty (function template)