NAME¶

std::forward_list - std::forward_list

Synopsis¶

Defined in header <forward_list>
template<

class T, (1) (since C++11)
class Allocator = std::allocator<T>

> class forward_list;
namespace pmr {

template< class T >
using forward_list = std::forward_list<T, (2) (since C++17)
std::pmr::polymorphic_allocator<T>>;

}

std::forward_list is a container that supports fast insertion and removal of
elements from anywhere in the container. Fast random access is not supported. It is
implemented as a singly-linked list. Compared to std::list this container provides
more space efficient storage when bidirectional iteration is not needed.

Adding, removing and moving the elements within the list, or across several lists,
does not invalidate the iterators currently referring to other elements in the list.
However, an iterator or reference referring to an element is invalidated when the
corresponding element is removed (via erase_after) from the list.

std::forward_list meets the requirements of Container (except for the size member
function and that operator=='s complexity is always linear), AllocatorAwareContainer
and SequenceContainer.

Template parameters¶

The type of the elements.

The requirements that are imposed on the elements depend on the
actual operations performed on the container. Generally, it is (until
required that element type is a complete type and meets the C++17)
requirements of Erasable, but many member functions impose
stricter requirements.
The requirements that are imposed on the elements depend on the
actual operations performed on the container. Generally, it is
required that element type meets the requirements of Erasable, but
T - many member functions impose stricter requirements. This container
(but not its members) can be instantiated with an incomplete
element type if the allocator satisfies the allocator completeness (since
requirements. C++17)

Feature-test macro Value Std Feature
Minimal
__cpp_lib_incomplete_container_elements 201505L (C++17) incomplete
type
support

An allocator that is used to acquire/release memory and to
construct/destroy the elements in that memory. The type must meet the
requirements of Allocator.
Allocator - The behavior is undefined
(until C++20)
The program is ill-formed
(since C++20) if Allocator::value_type is not the same as T.

Member types¶

Member type Definition
value_type T
allocator_type Allocator
size_type Unsigned integer type (usually std::size_t)
difference_type Signed integer type (usually std::ptrdiff_t)
reference value_type&
const_reference const value_type&
pointer std::allocator_traits<Allocator>::pointer
const_pointer std::allocator_traits<Allocator>::const_pointer
iterator LegacyForwardIterator to value_type
const_iterator LegacyForwardIterator to const value_type

Member functions¶

constructor constructs the forward_list
(public member function)
destructor destructs the forward_list
(public member function)
operator= assigns values to the container
(public member function)
assign assigns values to the container
(public member function)
assign_range assigns a range of values to the container
(C++23) (public member function)
get_allocator returns the associated allocator
(public member function)

Element access¶

front access the first element
(public member function)

Iterators¶

before_begin returns an iterator to the element before beginning
cbefore_begin (public member function)
begin returns an iterator to the beginning
cbegin (public member function)
end returns an iterator to the end
cend (public member function)

Capacity¶

empty checks whether the container is empty
(public member function)
max_size returns the maximum possible number of elements
(public member function)

Modifiers¶

clear clears the contents
(public member function)
insert_after inserts elements after an element
(public member function)
emplace_after constructs elements in-place after an element
(public member function)
insert_range_after inserts a range of elements after an element
(C++23) (public member function)
erase_after erases an element after an element
(public member function)
push_front inserts an element to the beginning
(public member function)
emplace_front constructs an element in-place at the beginning
(public member function)
prepend_range adds a range of elements to the beginning
(C++23) (public member function)
pop_front removes the first element
(public member function)
resize changes the number of elements stored
(public member function)
swap swaps the contents
(public member function)

Operations¶

merge merges two sorted lists
(public member function)
splice_after moves elements from another forward_list
(public member function)
remove removes elements satisfying specific criteria
remove_if (public member function)
reverse reverses the order of the elements
(public member function)
unique removes consecutive duplicate elements
(public member function)
sort sorts the elements
(public member function)

Non-member functions¶

operator==
operator!=
operator<
operator<=
operator>
operator>= lexicographically compares the values of two
operator<=> forward_lists
(C++11) (function template)
(C++11)(removed in C++20)
(C++11)(removed in C++20)
(C++11)(removed in C++20)
(C++11)(removed in C++20)
(C++11)(removed in C++20)
(C++20)
std::swap(std::forward_list) specializes the std::swap algorithm
(C++11) (function template)
erase(std::forward_list) erases all elements satisfying specific criteria
erase_if(std::forward_list) (function template)
(C++20)

Deduction guides (since C++17)

Notes¶

Feature-test macro Value Std Feature
__cpp_lib_containers_ranges 202202L (C++23) Ranges construction and insertion for
containers

Example¶

This section is incomplete
Reason: no example

Category:¶

* Todo no example