std::vector::empty

 

C++

Language

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Regular expressions library (C++11)

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Thread support library (C++11)

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Technical Specifications

 

Containers library

array (C++11)

vector

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list

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unordered_multiset (C++11)

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std::vector

Member functions

vector::vector

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Element access

vector::at

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vector::data (C++11)

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 (C++11)

Modifiers

vector::clear

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vector::erase

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vector::pop_back

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vector::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::vector<int> contains any elements:

Run this code

#include <vector>
#include <iostream>
 
int main()
{
    std::vector<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)