`<forward_list>`

[added with C++11]

namespace std {
template<class Ty, class Alloc>
    class forward_list;

        // TEMPLATE FUNCTIONS
template<class Ty, class Alloc>
    bool operator==(
        const forward_list<Ty, Alloc>& lhs,
        const forward_list<Ty, Alloc>& rhs);
template<class Ty, class Alloc>
    bool operator!=(
        const forward_list<Ty, Alloc>& lhs,
        const forward_list<Ty, Alloc>& rhs);
template<class Ty, class Alloc>
    bool operator<(
        const forward_list<Ty, Alloc>& lhs,
        const forward_list<Ty, Alloc>& rhs);
template<class Ty, class Alloc>
    bool operator>(
        const forward_list<Ty, Alloc>& lhs,
        const forward_list<Ty, Alloc>& rhs);
template<class Ty, class Alloc>
    bool operator<=(
        const forward_list<Ty, Alloc>& lhs,
        const forward_list<Ty, Alloc>& rhs);
template<class Ty, class Alloc>
    bool operator>=(
        const forward_list<Ty, Alloc>& lhs,
        const forward_list<Ty, Alloc>& rhs);

template<class Ty, class Alloc>
    void swap(
        forward_list<Ty, Alloc>& lhs,
        forward_list<Ty, Alloc>& rhs);
}  // namespace std

Include the STL standard header <forward_list> to define the container template class forward_list and several supporting templates.

`forward_list`

allocator_type · assign · cbefore_begin · before_begin · begin · cbegin · cend · clear · const_iterator · const_pointer · const_reference · difference_type · emplace_after · emplace_front · empty · end · erase_after · front · get_allocator · insert_after · iterator · forward_list · max_size · merge · operator= · pointer · pop_front · previous · push_front · reference · remove · remove_if · resize · reverse · size_type · sort · splice_after · swap · unique · value_type

template<class Ty, class Alloc = allocator<Ty> >
    class forward_list {
public:
    typedef Alloc allocator_type;
    typedef typename Alloc::pointer pointer;
    typedef typename Alloc::const_pointer
        const_pointer;
    typedef typename Alloc::reference reference;
    typedef typename Alloc::const_reference const_reference;
    typedef typename Alloc::value_type value_type;
    typedef typename Alloc::size_type size_type;
    typedef typename Alloc::difference_type difference_type;

    typedef T0 iterator;
    typedef T1 const_iterator;

    forward_list();
    explicit forward_list(const Alloc& al);

    explicit forward_list(size_type n);
    forward_list(size_type n, const Ty& val);
    forward_list(size_type n, const Ty& val,
        const Alloc& al);
    forward_list(const forward_list& right);
    forward_list(const forward_list& right,
        const Alloc& al);
    forward_list(list&& right);
    forward_list(list&& right,
        const Alloc& al);

    template<class InIt>
        forward_list(InIt first, InIt last);
    template<class InIt>
        forward_list(InIt first, InIt last,
            const Alloc& al);

    forward_list(initializer_list<Ty> init)
    forward_list(initializer_list<Ty> init,
        const Alloc& al);
    forward_list(list&& right);
    forward_list(list&& right,
        const Alloc& al);

    forward_list& operator=(const forward_list& right);
    forward_list& operator=(initializer_list<Ty> init)
    forward_list& operator=(forward_list&& right);

    iterator before_begin() noexcept;
    const_iterator before_begin() const noexcept;
    iterator begin();
    const_iterator begin() const;
    iterator end();
    const_iterator end() const;

    const_iterator cbefore_begin() noexcept;
    const_iterator cbegin() const;
    const_iterator cend() const;

    iterator previous(const_iterator it);
    const_iterator previous(const_iterator it) const;

    void resize(size_type n);
    void resize(size_type n, const Ty& x);
    size_type max_size() const;
    bool empty() const;

    Alloc get_allocator() const;

    reference front();
    const_reference front() const;

    void push_front(const Ty& val);
    void push_front(Ty&& val);
    template<class... Valty>
        void emplace_front(Valty&&... val);
    void pop_front();

    template<class InIt>
        void assign(InIt first, InIt last);
    void assign(size_type n, const Ty& x);
    void assign(initializer_list<Ty> init)

    iterator insert_after(const_iterator where, const Ty& x);
    iterator insert_after(const_iterator where, size_type n, const Ty& x);
    template<class InIt>
        iterator insert_after(const_iterator where, InIt first, InIt last);
    iterator insert_after(const iterator where,
        initializer_list<Ty> init)
    iterator insert_after(const_iterator where, Ty&& x);

    template<class... Valty>
        iterator emplace_after(const_iterator where, Valty&&... val);

    iterator erase_after(const_iterator where);
    iterator erase_after(const_iterator first,
        const_iterator last);
    void clear() noexcept;

    void swap(forward_list& right);

    void splice_after(const_iterator where,
        forward_list& x);
    void splice_after(const_iterator where,
        forward_list& x, iterator first);
    void splice_after(const_iterator where,
        forward_list& x, iterator first, iterator last);

    void splice_after(const_iterator where,
        forward_list&& x);
    void splice_after(const_iterator where,
        forward_list&& x, iterator first);
    void splice_after(const_iterator where,
        forward_list&& x, iterator first, iterator last);

    void remove(const Ty& x);
    template<class Pred>
        void remove_if(Pred pr);
    void unique();
    template<class Pred>
        void unique(Pred pr);

    void merge(forward_list& x);
    template<class Pred>
        void merge(forward_list& x, Pred pr);

    void merge(forward_list&& x);
    template<class Pred>
        void merge(forward_list&& x, Pred pr);

    void sort();
    template<class Pred>
        void sort(Pred pr);
    void reverse() noexcept;
    };

The template class describes an object that controls a varying-length sequence of elements of type Ty. The sequence is stored as a singly linked list of elements, each containing a member of type Ty.

The object allocates and frees storage for the sequence it controls through a stored allocator object of class Alloc. Such an allocator object must have the same external interface as an object of template class allocator.

List reallocation occurs when a member function must insert, erase or splice elements of the controlled sequence. In all such cases, only iterators or references that designate erased or spliced elements of the controlled sequence become invalid.

All additions to the controlled sequence occur as if by calls to insert_after, which is the only member function that calls the constructor Ty(const Ty&). If such an expression throws an exception, the container object inserts no new elements and rethrows the exception. Thus, an object of template class forward_list is left in a known state when such exceptions occur.

`forward_list::allocator_type`

typedef Alloc allocator_type;

The type is a synonym for the template parameter Alloc.

`forward_list::assign`

template<class InIt>
    void assign(InIt first, InIt last);
void assign(size_type n, const Ty& x);
void assign(initializer_list<Ty> init)

If InIt is an integer type, the first member function behaves the same as assign((size_type)first, (Ty)last). Otherwise, the first member function replaces the sequence controlled by *this with the sequence [first, last), which must not overlap the initial controlled sequence. The second member function replaces the sequence controlled by *this with a repetition of n elements of value x.

The third member function replaces the controlled sequence from an object of class initializer_list<Ty>.

`forward_list::before_begin`

const_iterator before_begin() const noexcept;
iterator before_begin() noexcept;

The member function returns a forward iterator that points just before the first element of the sequence (or just before the end of an empty sequence).

`forward_list::begin`

const_iterator begin() const;
iterator begin();

The member function returns a forward iterator that points at the first element of the sequence (or just beyond the end of an empty sequence).

`forward_list::cbefore_begin`

const_iterator cbefore_begin() const noexcept;

The member function returns a forward iterator that points just before the first element of the sequence (or just before the end of an empty sequence).

`forward_list::cbegin`

const_iterator cbegin() const;

The member functions return a forward iterator that points at the first element of the sequence (or just beyond the end of an empty sequence).

`forward_list::cend`

const_reference cend() const;

The member functions return a forward iterator that points just beyond the end of the sequence.

`forward_list::clear`

void clear() noexcept;

The member function calls erase_after( before_begin(), end()).

`forward_list::const_iterator`

typedef T1 const_iterator;

The type describes an object that can serve as a constant forward iterator for the controlled sequence. It is described here as a synonym for the implementation-defined type T1.

`forward_list::const_pointer`

typedef typename Alloc::const_pointer
    const_pointer;

The type describes an object that can serve as a constant pointer to an element of the controlled sequence.

`forward_list::const_reference`

typedef typename Alloc::const_reference const_reference;

The type describes an object that can serve as a constant reference to an element of the controlled sequence.

`forward_list::difference_type`

typedef typename Alloc::difference_type difference_type;

The signed integer type describes an object that can represent the difference between the addresses of any two elements in the controlled sequence.

`forward_list::emplace_after`

template<class... Valty>
    iterator emplace_after(const_iterator where, Valty&&... val);

The member function effectively returns insert_after(where, value_type(forward<Valty>(val)...)), except that the element value is constructed in place.

`forward_list::emplace_front`

template<class... Valty>
    void emplace_front(Valty&&... val);

The member function effectively returns insert_after(before_begin(), value_type(forward<Valty>(val)...)), except that the element value is constructed in place.

If an exception is thrown, the container is left unaltered and the exception is rethrown.

`forward_list::empty`

bool empty() const;

The member function returns true for an empty controlled sequence.

`forward_list::end`

const_iterator end() const;
iterator end();

The member function returns a forward iterator that points just beyond the end of the sequence.

`forward_list::erase_after`

iterator erase_after(const_iterator where);
iterator erase_after(const_iterator first,
    const_iterator last);

The first member function removes the element of the controlled sequence just after where. The second member function removes the elements of the controlled sequence in the range (first, last) (neither end point is included). Both return an iterator that designates the first element remaining beyond any elements removed, or end() if no such element exists.

Erasing N elements causes N destructor calls. Reallocation occurs, so iterators and references become invalid for the erased elements.

The member functions throws nothing.

`forward_list::forward_list`

forward_list();
explicit forward_list(const Alloc& al);

explicit forward_list(size_type n);
forward_list(size_type n, const Ty& val);
forward_list(size_type n, const Ty& val,
    const Alloc& al);

forward_list(const forward_list& right);
forward_list(const forward_list& right,
    const Alloc& al);
forward_list(forward_list&& right);
forward_list(forward_list&& right,
    const Alloc& al);

template<class InIt>
    forward_list(InIt first, InIt last);
template<class InIt>
    forward_list(InIt first, InIt last, const Alloc& al);

forward_list(initializer_list<Ty> init)
forward_list(initializer_list<Ty> init,
    const Alloc& al);

All constructors store an allocator object and initialize the controlled sequence. The allocator object is the argument al, if present. Otherwise, for the copy and move constructors, it is right.get_allocator(). Otherwise, it is Alloc().

The first two constructors specify an empty initial controlled sequence.

The next three constructors specify a repetition of count elements of value val, if specified. Otherwise the repeated value is Ty().

The next four constructors specify a copy of the sequence controlled by right. The last two of these constructors are the same as the first two, but with an rvalue reference.

The next two constructors specify the sequence [first, last).

The last two constructors specify the initial controlled sequence with an object of class initializer_list<Ty>.

`forward_list::front`

reference front();
const_reference front() const;

The member function returns a reference to the first element of the controlled sequence, which must be non-empty.

`forward_list::get_allocator`

Alloc get_allocator() const;

The member function returns the stored allocator object.

`forward_list::insert_after`

iterator insert_after(const_iterator where, const Ty& x);
iterator insert_after(const_iterator where, size_type n, const Ty& x);
template<class InIt>
    iterator insert_after(const_iterator where, InIt first, InIt last);
itereator insert_after(const iterator where,
    initializer_list<Ty> init)
iterator insert_after(const_iterator where, Ty&& x);

Each of the member functions inserts, just after the element pointed to by where in the controlled sequence, a sequence specified by the remaining operands, and returns an iterator that designates the last inserted element. The first member function inserts a single element with value x. The second member function inserts a repetition of n elements of value x.

If InIt is an integer type, the third member function behaves the same as insert(it, (size_type)first, (Ty)last). Otherwise, it inserts the sequence [first, last), which must not overlap the initial controlled sequence.

The fourth member function inserts the sequence specified by an object of class initializer_list<Ty>.

The last member function is the same as the first, but with an rvalue reference.

Inserting N elements causes N constructor calls. Reallocation occurs, but no iterators or references become invalid.

If an exception is thrown during the insertion of one or more elements, the container is left unaltered and the exception is rethrown.

`forward_list::iterator`

typedef T0 iterator;

The type describes an object that can serve as a forward iterator for the controlled sequence. It is described here as a synonym for the implementation-defined type T0.

`forward_list::max_size`

size_type max_size() const;

The member function returns the length of the longest sequence that the object can control.

`forward_list::merge`

void merge(forward_list& x);
template<class Pred>
    void merge(forward_list& x, Pred pr);

void merge(forward_list&& x);
template<class Pred>
    void merge(forward_list&& x, Pred pr);

The first two member functions remove all elements from the sequence controlled by x and insert them in the controlled sequence. Both sequences must be ordered by the same predicate, described below. The resulting sequence is also ordered by that predicate.

The last two member functions are the same as the first, but with rvalue references.

No pairs of elements in the original controlled sequence are reversed in the resulting controlled sequence. If a pair of elements in the resulting controlled sequence compares equal (!(*Pi < *Pj) && !(*Pj < *Pi)), an element from the original controlled sequence appears before an element from the sequence controlled by x.

An exception occurs only if pr throws an exception. In that case, the controlled sequence is left in unspecified order and the exception is rethrown.

`forward_list::operator=`

forward_list& operator=(const forward_list& right);
forward_list& operator=(initializer_list<Ty> init)
forward_list& operator=(forward_list&& right);

The first member operator replaces the controlled sequence with a copy of the sequence controlled by right.

The second member operator replaces the controlled sequence from an object of class initializer_list<Ty>.

The third member operator is the same as the first, but with an rvalue reference.

`forward_list::pointer`

typedef typename Alloc::pointer pointer;

The type describes an object that can serve as a pointer to an element of the controlled sequence.

`forward_list::pop_front`

void pop_front();

The member function removes the first element of the controlled sequence, which must be non-empty.

The member function never throws an exception.

`forward_list::previous`

iterator previous(const_iterator it);
const_iterator previous(const_iterator it) const;

The member function returns an iterator that designates the element immediately preceding it, if possible; otherwise it returns end(). This operation takes time proportional to the number of elements in the controlled sequence (linear time complexity).

`forward_list::push_front`

void push_front(const Ty& val);
void push_front(Ty&& val);

The member function inserts an element with value val at the beginning of the controlled sequence.

If an exception is thrown, the container is left unaltered and the exception is rethrown.

`forward_list::reference`

typedef typename Alloc::reference reference;

The type describes an object that can serve as a reference to an element of the controlled sequence.

`forward_list::remove`

void remove(const Ty& x);

The member function removes from the controlled sequence all elements, designated by the iterator P, for which *P == x.

The member function never throws an exception.

`forward_list::remove_if`

template<class Pred>
    void remove_if(Pred pr);

The member function removes from the controlled sequence all elements, designated by the iterator P, for which pr(*P) is true.

An exception occurs only if pr throws an exception. In that case, the controlled sequence is left in an unspecified state and the exception is rethrown.

`forward_list::resize`

void resize(size_type n);
void resize(size_type n, const Ty& x);

The member functions both ensure that the number of elements in the list henceforth is n. If it must make the controlled sequence longer, the first member function appends elements with value T(), while the second member function appends elements with value x. To make the controlled sequence shorter, both member functions effectively call erase_after(begin() + n - 1, end()).

`forward_list::reverse`

void reverse() noexcept;

The member function reverses the order in which elements appear in the controlled sequence.

`forward_list::size_type`

typedef typename Alloc::size_type size_type;

The unsigned integer type describes an object that can represent the length of any controlled sequence.

`forward_list::sort`

void sort();
template<class Pred>
    void sort(Pred pr);

Both member functions order the elements in the controlled sequence by a predicate, described below.

For the iterators Pi and Pj designating elements at positions i and j, the first member function imposes the order !(*Pj < *Pi) whenever i < j. (The elements are sorted in ascending order.) The member template function imposes the order !pr(*Pj, *Pi) whenever i < j. No ordered pairs of elements in the original controlled sequence are reversed in the resulting controlled sequence. (The sort is stable.)

An exception occurs only if pr throws an exception. In that case, the controlled sequence is left in unspecified order and the exception is rethrown.

`forward_list::splice_after`

void splice_after(const_iterator where,
    forward_list& x);
void splice_after(const_iterator where,
    forward_list& x, iterator first);
void splice_after(const_iterator where,
    forward_list& x, iterator first, iterator last);

void splice_after(const_iterator where,
    forward_list&& x);
void splice_after(const_iterator where,
    forward_list&& x, iterator first);
void splice_after(const_iterator where,
    forward_list&& x, iterator first, iterator last);

The first member function inserts the sequence controlled by x just after the element in the controlled sequence pointed to by where. It also removes all elements from x. (&x must not equal this.)

The second member function removes the element just after first in the sequence controlled by x and inserts it just after the element in the controlled sequence pointed to by where. (If where == first || where == ++first, no change occurs.)

The third member function inserts the subrange designated by (first, last) from the sequence controlled by x just after the element in the controlled sequence pointed to by where. It also removes the original subrange from the sequence controlled by x. (If &x == this, the range (first, last) must not include the element pointed to by where.)

If the third member function inserts N elements, and &x != this, an object of class iterator is incremented N times. For all splice_after member functions, if get_allocator() == str.get_allocator(), no exception occurs. Otherwise, a copy and a destructor call also occur for each inserted element.

The last three member functions are the same as the first, but with rvalue references.

No iterators or references that designate spliced elements become invalid.

The member functions throw nothing.

`forward_list::swap`

void swap(forward_list& right);

The member function swaps the controlled sequences between *this and right. If get_allocator() == right.get_allocator(), it does so in constant time, it throws no exceptions, and it invalidates no references, pointers, or iterators that designate elements in the two controlled sequences. Otherwise, it performs a number of element assignments and constructor calls proportional to the number of elements in the two controlled sequences.

`forward_list::unique`

void unique();
template<class Pred>
    void unique(Pred pr);

The first member function removes from the controlled sequence every element that compares equal to its preceding element. For the iterators Pi and Pj designating elements at positions i and j, the second member function removes every element for which i + 1 == j && pr(*Pi, *Pj).

For a controlled sequence of length N (> 0), the predicate pr(*Pi, *Pj) is evaluated N - 1 times.

An exception occurs only if pr throws an exception. In that case, the controlled sequence is left in an unspecified state and the exception is rethrown.

`forward_list::value_type`

typedef typename Alloc::value_type value_type;

The type is a synonym for the template parameter Ty.

`operator!=`

template<class Ty, class Alloc>
    bool operator!=(
        const forward_list <Ty, Alloc>& lhs,
        const forward_list <Ty, Alloc>& rhs);

The template function returns !(lhs == rhs).

`operator==`

template<class Ty, class Alloc>
    bool operator==(
        const forward_list <Ty, Alloc>& lhs,
        const forward_list <Ty, Alloc>& rhs);

The template function overloads operator== to compare two objects of template class forward_list. The function returns distance( lhs.begin(), end()) == distance(rhs.begin(), rhs.end()) && equal(lhs. begin(), lhs. end(), rhs.begin()).

`operator<`

template<class Ty, class Alloc>
    bool operator<(
        const forward_list <Ty, Alloc>& lhs,
        const forward_list <Ty, Alloc>& rhs);

The template function overloads operator< to compare two objects of template class forward_list. The function returns lexicographical_compare(lhs. begin(), lhs. end(), rhs.begin(), rhs.end()).

`operator<=`

template<class Ty, class Alloc>
    bool operator<=(
        const forward_list <Ty, Alloc>& lhs,
        const forward_list <Ty, Alloc>& rhs);

The template function returns !(rhs < lhs).

`operator>`

template<class Ty, class Alloc>
    bool operator>(
        const forward_list <Ty, Alloc>& lhs,
        const forward_list <Ty, Alloc>& rhs);

The template function returns rhs < lhs.

`operator>=`

template<class Ty, class Alloc>
    bool operator>=(
        const forward_list <Ty, Alloc>& lhs,
        const forward_list <Ty, Alloc>& rhs);

The template function returns !(lhs < rhs).

`swap`

template<class Ty, class Alloc>
    void swap(
        forward_list <Ty, Alloc>& lhs,
        forward_list <Ty, Alloc>& rhs);

The template function executes lhs.swap(rhs).

See also the Table of Contents and the Index.