Overview

template< class T >
class initializer_list;

std::initializer_list is a light container that holds objects from list initialization or braced initialization.

Memory

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Technical details

Feature testing macros

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Technical definition

An object of type std::initializer_list<T> is a lightweight proxy object that provides access to an array of objects of type const T.

A std::initializer_list<T> object is automatically constructed when:

• A braced-init-list is used to list-initialize an object, where the corresponding constructor accepts an std::initializer_list<T> parameter
• A braced-init-list is used as the right operand of assignment or as a function call argument, and the corresponding assignment operator/function accepts an std::initializer_list<T> parameter
• A braced-init-list is bound to auto, including in a ranged for loop

Initializer lists may be implemented as a pair of pointers or pointer and length.

note

Copying a std::initializer_list does not copy the underlying objects.

The underlying array is a temporary array of type const T[N], in which each element is copy-initialized (except that narrowing conversions are invalid) from the corresponding element of the original initializer list. The lifetime of the underlying array is the same as any other temporary object, except that initializing an initializer list object from the array extends the lifetime of the array exactly like binding a reference to a temporary (with the same exceptions, such as for initializing a non-static class member). The underlying array may be allocated in read-only memory.

danger

The program is ill-formed

if an explicit or partial specialization of std::initializer_list is declared.

std::initializer_list

Defined in

initializer_list

Template parameters

pub

T

Type of the elements.

Type names

pub	value_type	T
pub	reference	const T&
pub	const_reference	const T&
pub	size_type	Unsigned integer type (usually std::size_t)
pub	iterator	const T*
pub	const_iterator	const T*

Member functions

pub	(constructors)	Constructs a initializer list.
pub	(destructor)	Destroys the initializer list.

Capacity

pub

size

Returns the number of elements.

Iterators

pub	begin cbegin  (since C++11)	Returns an iterator/const_iterator to the beginning.
pub	end cend  (since C++11)	Returns an iterator/const_iterator to the end.

Non-member functions

pub	std::begin (std::initializer_list)	An overload for a std::begin.
pub	std::end (std::initializer_list)	An overload for a std::end.

Free function templates overloaded for std::initializer_list

pub	rbegin crbegin  (since C++14)	Returns a reverse iterator/const_iterator to the beginning.
pub	rend crend  (since C++14)	Returns a reverse iterator/const_iterator to the end.
pub	empty  (since C++17)	Returns true if the initializer list is empty, otherwise false.
pub	data  (since C++17)	Returns a pointer to the first element of the underlying array.

Examples

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