std::initializer_list (C++11)

In a Nutshell

A lightweight, read-only proxy object that allows us to pass an arbitrary number of same-type initial values to containers or custom classes using braces {}.

Header

#include <initializer_list>

Core API Quick Reference

Operation	Signature	Description
Construction	initializer_list() noexcept	Creates an empty list (typically implicitly constructed by the compiler)
Element count	std::size_t size() const noexcept	Returns the number of elements in the list
Begin pointer	const T* begin() const noexcept	Pointer to the first element
End pointer	const T* end() const noexcept	Pointer to one past the last element
Begin iterator	const T* begin(std::initializer_list<T> il) noexcept	Overloaded std::begin
End iterator	const T* end(std::initializer_list<T> il) noexcept	Overloaded std::end

Minimal Example

// Standard: C++11
#include <iostream>
#include <initializer_list>
#include <vector>

struct Container {
    std::vector<int> v;
    Container(std::initializer_list<int> l) : v(l) {}
    void append(std::initializer_list<int> l) {
        v.insert(v.end(), l.begin(), l.end());
    }
};

int main() {
    Container c = {1, 2, 3}; // 隐式构造 initializer_list
    c.append({4, 5});
    for (int x : c.v) std::cout << x << ' ';
}

Embedded Applicability: High

• The underlying implementation typically contains only a pointer and a length (or two pointers), resulting in minimal memory overhead
• Copying std::initializer_list does not copy the underlying array; it only copies the proxy object itself, with no additional allocation overhead
• The underlying array may reside in read-only memory, making it suitable for initializing ROM-able static configuration tables

Compiler Support

GCC	Clang	MSVC
TBA	TBA	TBA

See Also

• Tutorial: Initializer Lists
• cppreference: std::initializer_list

---

Some content referenced from cppreference.com, licensed under CC-BY-SA 4.0