std::deque::empty

 

C++

Language

Standard library headers

Concepts

Utilities library

Strings library

Containers library

Algorithms library

Iterators library

Numerics library

Input/output library

Localizations library

Regular expressions library (C++11)

Atomic operations library (C++11)

Thread support library (C++11)

 

Containers library

array (C++11)

vector

deque

forward_list (C++11)

list

set

multiset

map

multimap

unordered_set (C++11)

unordered_multiset (C++11)

unordered_map (C++11)

unordered_multimap (C++11)

stack

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std::deque

Member functions

deque::deque

deque::~deque

deque::operator=

deque::assign

deque::get_allocator

Element access

deque::front

deque::back

Iterators

deque::begindeque::cbegin (C++11)

deque::enddeque::cend (C++11)

deque::rbegindeque::crbegin (C++11)

deque::renddeque::crend (C++11)

Capacity

deque::empty

deque::size

deque::max_size

deque::shrink_to_fit

Modifiers

deque::clear

deque::insert

deque::emplace

deque::erase

deque::push_front

deque::emplace_front

deque::pop_front

deque::push_back

deque::emplace_back

deque::pop_back

deque::resize

deque::swap

 

bool empty() const;

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

Parameters

(none)

Return value

true if the container is empty, false otherwise

Exceptions

(none)	(until C++11)
noexcept specification:   noexcept	(since C++11)

Complexity

Constant.

Example

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

Run this code

#include <deque>
#include <iostream>
 
int main()
{
    std::deque<int> numbers;
    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(): 1
After adding elements, numbers.empty(): 0

See also

size	returns the number of elements (public member function)