std::empty

Since C++17

Header: <array>

Returns whether the given range is empty.

# Declarations

template< class C >
constexpr auto empty( const C& c ) -> decltype(c.empty());

(since C++17)

template< class T, std::size_t N >
constexpr bool empty( const T (&array)[N] ) noexcept;

(since C++17)

template< class E >
constexpr bool empty( std::initializer_list<E> il ) noexcept;

(since C++17)

# Parameters

c: a container or view with an empty member function
array: an array of arbitrary type
il: an std::initializer_list

# Notes

The overload for std::initializer_list is necessary because it does not have a member function empty.

# Example

#include <iostream>
#include <vector>
 
template<class T>
void print(const T& container)
{
    if (std::empty(container))
        std::cout << "Empty\n";
    else
    {
        std::cout << "Elements:";
        for (const auto& element : container)
            std::cout << ' ' << element;
        std::cout << '\n';
    }
}
 
int main()
{
    std::vector<int> c = {1, 2, 3};
    print(c);
    c.clear();
    print(c);
 
    int array[] = {4, 5, 6};
    print(array);
 
    auto il = {7, 8, 9};
    print(il);
}

# See also

ranges::empty