std::initializer_list::initializer_list

 

C++

Language

Standard Library Headers

Freestanding and hosted implementations

Named requirements

Language support library

Concepts library (C++20)

Diagnostics library

Utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Numerics library

Input/output library

Localizations library

Regular expressions library (C++11)

Atomic operations library (C++11)

Thread support library (C++11)

Filesystem library (C++17)

Technical Specifications

 

Utilities library

Type support (basic types, RTTI, type traits)
Dynamic memory management
Error handling
Program utilities
Variadic functions
Library feature-test macros
Date and time
Function objects
initializer_list (C++11)
bitset
hash (C++11)
integer_sequence (C++14)
Relational operators (deprecated in C++20)
rel_ops::operator!=rel_ops::operator>rel_ops::operator<=rel_ops::operator>=
Comparisons (C++20)
strong_order weak_order partial_order strong_equal weak_equal	strong_ordering weak_ordering partial_ordering strong_equality weak_equality	is_eqis_neqis_ltis_lteqis_gtis_gteq
common_comparison_category
Common vocabulary types
pair tuple (C++11) apply (C++17) make_from_tuple (C++17)	optional (C++17) any (C++17) variant (C++17)
Swap, forward and move
swap
exchange (C++14)
forward (C++11)
move (C++11)
move_if_noexcept (C++11)
Elementary string conversions
to_chars (C++17)
from_chars (C++17)
chars_format (C++17)
Type operations
declval (C++11)
as_const (C++17)
launder (C++17)

 

std::initializer_list

Member functions

initializer_list::initializer_list

Capacity

initializer_list::size

Iterators

initializer_list::begin

initializer_list::end

Non-member functions

std::begin

std::end

std::rbegin (C++14)

std::rend (C++14)

 

initializer_list() noexcept;		(since C++11) (until C++14)
constexpr initializer_list() noexcept;		(since C++14)

Constructs an empty initializer list.

Parameters

(none)

Complexity

Constant

Example

Run this code

#include <iostream>
#include <initializer_list>
 
int main() 
{
    std::initializer_list<int> empty_list;
    std::cout << "empty_list.size(): " << empty_list.size() << '\n';
 
    // create initializer lists using list-initialization
    std::initializer_list<int> digits {1, 2, 3, 4, 5};
    std::cout << "digits.size(): " << digits.size() << '\n';
 
    // special rule for auto means 'fractions' has the
    // type std::initializer_list<double>
    auto fractions = {3.14159, 2.71828};
    std::cout << "fractions.size(): " << fractions.size() << '\n';
}

Output:

empty_list.size(): 0
digits.size(): 5
fractions.size(): 2

Notes

Despite a lack of constructors, it is possible to create non-empty initializer lists. Instances of std::initializer_list are implicitly constructed when:

• a braced-init-list is used in list-initialization, including function-call list initialization and assignment expressions (not to be confused with constructor initializer lists)
• a braced-init-list is bound to auto, including in a ranged for loop