C++ Library - <forward_list>

Introduction

forward_list is a popularly used sequence container. Container is an object that holds data of same type. forward_list container is implemented as singly linked-list, hence it provides unidirectional sequential access to it's data.

forward_list doesn't provide fast random access, it only supports sequential access in only one directions. forward_list allows insertion and deletion operation anywhere within a sequence in constant time.

Elements of forward_list can be scattered in different chunks of memory. Container stores necessary information to allow sequential access to it's data. forward_lists can shrink or expand as needed from both ends at run time. The storage requirement is fulfilled automatically by internal allocator.

Zero sized forward_lists are also valid. In that case forward_list.begin() and forward_list.end() points to same location. But behavior of calling front() is undefined.

Definition

Below is definition of std::forward_list from <forward_list> header file

template < class T, class Alloc = allocator<T> > class forward_list;

Parameters

T − Type of the element contained.

T may be substituted by any other data type including user-defined type.
Alloc − Type of allocator object.

By default, the allocator class template is used, which defines the simplest memory allocation model and is value-independent.

Member types

Following member types can be used as parameters or return type by member functions.

Sr.No.	Member types	Definition
1	value_type	T (First parameter of the template)
2	allocator_type	Alloc (Second parameter of the template)
3	reference	value_type&
4	const_reference	const value_type&
5	pointer	value_type*
6	const_pointer	const value_type*
7	iterator	a random access iterator to value_type
8	const_iterator	a random access iterator to const value_type
9	size_type	size_t
10	difference_type	ptrdiff_t

Functions from <forward_list>

Below is list of all methods from <forward_list> header.

Constructors

Sr.No.	Method & Description
1	forward_list::forward_list `default constructor` Constructs an empty forward_list with zero elements.
2	forward_list::forward_list `fill constructor` Constructs a new forward_list with `n` elements and assigns `val` to each element of forward_list.
3	forward_list::forward_list `fill constructor` Constructs a new forward_list with `n` elements and assign zero value to each element of forward_list.
4	forward_list::forward_list `range constructor` Constructs a forward_list with as many elements as in range of `first` to `last`.
5	forward_list::forward_list `copy constructor` Constructs a forward_list with copy of each elements present in existing list.
6	forward_list::forward_list `move constructor` Constructs a forward_list with the contents of `other` using move semantics.
7	forward_list::forward_list `initializer list constructor` Constructs a forward_list from initialize list.

Destructor

Sr.No.	Method & Description
1	forward_list::~forward_list Destroys forward_list object by deallocating it's memory.

Member functions

Sr.No.	Method & Description
1	forward_list::assign `range version` Assigns new value to forward_list by replacing old ones.
2	forward_list::assign `fill version` Assigns new values to forward_list by replacing old ones.
3	forward_list::assign `initializer list version` Assigns new values to forward_list by replacing old ones.
4	forward_list::before_begin Returns a random access iterator which points to the position before the first element of the forward_list.
5	forward_list::begin Returns a random access iterator which points to the first element of the forward_list.
6	forward_list::cbefore_begin Returns a constant random access iterator which points to the position before the first element of the forward_list.
7	forward_list::cbegin Returns a constant random access iterator which points to the beginning of the forward_list.
8	forward_list::cend Returns a constant random access iterator which points to the end of the forward_list.
9	forward_list::clear Destroys the forward_list by removing all elements from the forward_list and sets size of forward_list to zero.
10	forward_list::emplace_after Constructs and inserts new element after `position` in the forward_list and increases size of forward_list by one.
11	forward_list::emplace_front Inserts new element at the beginning of the forward_list and increases size of forward_list by one.
12	forward_list::empty Tests whether forward_list is empty or not.
13	forward_list::end Returns a random access iterator which points to the last element of the forward_list.
14	forward_list::erase_after `position version` Removes single element after `position` from the the forward_list.
15	forward_list::erase `range version` Removes range of element from the the forward_list.
16	forward_list::front Returns a reference to the first element of the forward_list.
17	forward_list::get_allocator Returns an allocator associated with forward_list
18	forward_list::insert_after `single element version` Extends iterator by inserting new element after `position` in forward_list
19	forward_list::insert_after `move version` Extends iterator by inserting new element after `position` in forward_list
20	forward_list::insert_after `fill version` Extends iterator by inserting new element after `position` in forward_list
21	forward_list::insert_after `range version` Extends iterator by inserting new element after `position` in forward_list
22	forward_list::insert_after `initializer list version` Extends iterator by inserting new element after `position` in forward_list
23	forward_list::max_size Returns the maximum number of elements can be held by forward_list.
24	forward_list::merge Merges two sorted forward_lists into one.
25	forward_list::merge `move version` Merges two sorted forward_lists into one.
26	forward_list::merge `compare function` Merges two sorted forward_lists into one.
27	forward_list::merge `compare function move version` Merges two sorted forward_lists into one by using move semantics.
28	forward_list::operator= `copy version` Assigns new contents to the forward_list by replacing old ones.
29	forward_list::operator= `move version` Assign new contents to the forward_list by replacing old ones.
30	forward_list::operator= `initializer list version` Assign new contents to the forward_list by replacing old ones.
31	forward_list::pop_front Removes first element from forward_list.
32	forward_list::push_front `copy version` Inserts new element at the beginning of forward_list.
33	forward_list::push_front `move version` Inserts new element at the beginning of forward_list.
34	forward_list::remove removes element(s) from the forward_list that matches the value.
35	forward_list::remove_if removes elements from the forward_list that fulfills the condition.
36	forward_list::resize Changes the size of forward_list.
37	forward_list::resize `value version` Changes the size of forward_list.
38	forward_list::reverse Reverses the order of the elements present in the forward_list.
39	forward_list::sort Sorts the elements of the forward_list.
40	forward_list::sort `compare function` Sorts the elements of the forward_list.
41	forward_list::splice_after Transfers all elements from forward_list to *this.
42	forward_list::splice_after `move version` Transfers all elements from forward_list `x` to `*this` by using move semantics.
43	forward_list::splice_after `single element` Transfers a element pointed to by iterator `i` from forward_list `x` into `*this`.
44	forward_list::splice_after `single element move version` Transfers the element pointed to by iterator `i` from forward_list `x` into `*this` by using move semantics.
45	forward_list::splice_after `range version` Transfers the elements in the range of `first` to `last` from `x` to `*this`.
46	forward_list::splice `range and move version` Transfers the elements in the range of `first` to `last` from `x` to `*this` by using move semantics.
47	forward_list::swap Exchanges the content of a forward_list with contents of another forward_list `x`.
48	forward_list::unique Removes all consecutive duplicate elements from the forward_list.
49	forward_list::unique Removes all consecutive duplicate elements from the forward_list.

Non-member overloaded functions

Sr.No.	Method & Description
1	operator== Tests whether two forward_lists are equal or not.
2	operator!= Tests whether two forward_lists are equal or not.
3	operator< Tests whether first forward_list is less than other or not.
4	operator<= Tests whether first forward_list is less than or equal to other or not.
5	operator> Tests whether first forward_list is greater than other or not.
6	operator>= Tests whether first forward_list is greater than or equal to other or not.
7	swap Exchanges the contents of two forward_list.

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