std::initializer_list<T>::empty

 

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Language support Type support (basic types, RTTI) Library feature-test macros (C++20) Program utilities Variadic functions initializer_list (C++11) is_constant_evaluated (C++20) is_within_lifetime (C++26) source_location (C++20) Coroutine support (C++20) Contract support (C++26) Three-way comparison three_way_comparablethree_way_comparable_with (C++20)(C++20) strong_ordering (C++20) weak_ordering (C++20) partial_ordering (C++20) common_comparison_category (C++20) compare_three_way_result (C++20) compare_three_way (C++20) strong_order (C++20) weak_order (C++20) partial_order (C++20) compare_strong_order_fallback (C++20) compare_weak_order_fallback (C++20) compare_partial_order_fallback (C++20)     type_order (C++26) is_eqis_ltis_lteq (C++20)(C++20)(C++20) is_neqis_gtis_gteq (C++20)(C++20)(C++20)

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std::initializer_list

Member functions

initializer_list::initializer_list

Capacity

initializer_list::size

initializer_list::empty

Iterators

initializer_list::begin

initializer_list::end

initializer_list::data

 

bool empty() const noexcept;		(since C++11) (constexpr since C++14)

Checks whether the initializer_list is empty. Equivalent to return size() == 0;.

Return value

true if the initializer_list is empty, false otherwise.

Complexity

Constant

Notes

As for 2026-05-27, libstdc++ has not treated the addition of the empty function from P3016R6 as a defect report against C++11, and only adds empty since C++26.

Example

Run this code

#include <initializer_list>
#include <iostream>

constexpr std::initializer_list<int> il1{};
constexpr std::initializer_list<int> il2{3, 1, 4, 1, 5, 9};

int main()
{
    static_assert(il1.empty(), "");
    static_assert(!il2.empty(), "");

    std::cout << std::boolalpha
        << il1.empty() << '\n'
        << il2.empty() << '\n';
}

Output:

true
false

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR	Applied to	Behavior as published	Correct behavior
P3016R6	C++11	std::initializer_list lacked empty function	added

See also

size (C++11)

returns the number of elements in the initializer list (public member function)