std::forward_list<T,Allocator>::before_begin, cbefore_begin

 

C++

Compiler support

Freestanding and hosted

Language

Standard library

Standard library headers

Named requirements

Feature test macros (C++20)

Language support library

Concepts library (C++20)

Metaprogramming library (C++11)

Diagnostics library

General utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Numerics library

Localizations library

Input/output library

Filesystem library (C++17)

Regular expressions library (C++11)

Concurrency support library (C++11)

Technical specifications

Symbols index

External libraries

 

Containers library

Sequence

array (C++11)

vector

vector<bool>

deque

forward_list (C++11)

list

Associative

set

multiset

map

multimap

Unordered associative

unordered_set (C++11)

unordered_multiset (C++11)

unordered_map (C++11)

unordered_multimap (C++11)

Adaptors

stack

queue

priority_queue

flat_set (C++23)

flat_multiset (C++23)

flat_map (C++23)

flat_multimap (C++23)

Views

span (C++20)

mdspan (C++23)

Iterator invalidation

Member function table

Non-member function table

 

std::forward_list

Member functions

forward_list::forward_list

forward_list::~forward_list

forward_list::operator=

forward_list::assign

forward_list::assign_range (C++23)

forward_list::get_allocator

Element access

forward_list::front

Iterators

forward_list::before_beginforward_list::cbefore_begin

forward_list::beginforward_list::cbegin

forward_list::endforward_list::cend

Capacity

forward_list::empty

forward_list::max_size

Modifiers

forward_list::clear

forward_list::insert_after

forward_list::emplace_after

forward_list::insert_range_after (C++23)

forward_list::erase_after

forward_list::push_front

forward_list::emplace_front

forward_list::prepend_range (C++23)

forward_list::pop_front

forward_list::resize

forward_list::swap

Operations

forward_list::merge

forward_list::splice_after

forward_list::removeforward_list::remove_if

forward_list::reverse

forward_list::unique

forward_list::sort

Non-member functions

std::swap

eraseerase_if (C++20)(C++20)

operator==operator!=operator<operator>operator<=operator>=operator<=> (until C++20)(until C++20)(until C++20)(until C++20)(until C++20)(C++20)

Deduction guides(C++17)

 

iterator before_begin() noexcept;		(since C++11)
const_iterator before_begin() const noexcept;		(since C++11)
const_iterator cbefore_begin() const noexcept;		(since C++11)

Returns an iterator to the element before the first element of the container. This element acts as a placeholder, attempting to access it results in undefined behavior. The only usage cases are in functions insert_after(), emplace_after(), erase_after(), splice_after() and the increment operator: incrementing the before-begin iterator gives exactly the same iterator as obtained from begin()/cbegin().

Parameters

(none)

Return value

Iterator to the element before the first element.

Complexity

Constant.

See also

begin cbegin (C++11)	returns an iterator to the beginning (public member function)
end cend (C++11)	returns an iterator to the end (public member function)