A list is a sequence container that supports bidirectional iterators and allows constant time insert and erase operations anywhere within the sequence, with storage management handled automatically. Unlike vectors ([vector]) and deques ([deque]), fast random access to list elements is not supported, but many algorithms only need sequential access anyway.
A list satisfies all of the requirements of a container, of a reversible container (given in two tables in [container.requirements]), of a sequence container, including most of the optional sequence container requirements ([sequence.reqmts]), and of an allocator-aware container (Table [tab:containers.allocatoraware]). The exceptions are the operator[] and at member functions, which are not provided.265 Descriptions are provided here only for operations on list that are not described in one of these tables or for operations where there is additional semantic information.
namespace std {
template <class T, class Allocator = allocator<T> >
class list {
public:
// types:
typedef value_type& reference;
typedef const value_type& const_reference;
typedef implementation-defined iterator; // see [container.requirements]
typedef implementation-defined const_iterator; // see [container.requirements]
typedef implementation-defined size_type; // see [container.requirements]
typedef implementation-defined difference_type;// see [container.requirements]
typedef T value_type;
typedef Allocator allocator_type;
typedef typename allocator_traits<Allocator>::pointer pointer;
typedef typename allocator_traits<Allocator>::const_pointer const_pointer;
typedef std::reverse_iterator<iterator> reverse_iterator;
typedef std::reverse_iterator<const_iterator> const_reverse_iterator;
// [list.cons], construct/copy/destroy:
explicit list(const Allocator& = Allocator());
explicit list(size_type n);
list(size_type n, const T& value, const Allocator& = Allocator());
template <class InputIterator>
list(InputIterator first, InputIterator last, const Allocator& = Allocator());
list(const list& x);
list(list&& x);
list(const list&, const Allocator&);
list(list&&, const Allocator&);
list(initializer_list<T>, const Allocator& = Allocator());
~list();
list& operator=(const list& x);
list& operator=(list&& x);
list& operator=(initializer_list<T>);
template <class InputIterator>
void assign(InputIterator first, InputIterator last);
void assign(size_type n, const T& t);
void assign(initializer_list<T>);
allocator_type get_allocator() const noexcept;
// iterators:
iterator begin() noexcept;
const_iterator begin() const noexcept;
iterator end() noexcept;
const_iterator end() const noexcept;
reverse_iterator rbegin() noexcept;
const_reverse_iterator rbegin() const noexcept;
reverse_iterator rend() noexcept;
const_reverse_iterator rend() const noexcept;
const_iterator cbegin() const noexcept;
const_iterator cend() const noexcept;
const_reverse_iterator crbegin() const noexcept;
const_reverse_iterator crend() const noexcept;
// [list.capacity], capacity:
bool empty() const noexcept;
size_type size() const noexcept;
size_type max_size() const noexcept;
void resize(size_type sz);
void resize(size_type sz, const T& c);
// element access:
reference front();
const_reference front() const;
reference back();
const_reference back() const;
// [list.modifiers], modifiers:
template <class... Args> void emplace_front(Args&&... args);
void pop_front();
template <class... Args> void emplace_back(Args&&... args);
void push_front(const T& x);
void push_front(T&& x);
void push_back(const T& x);
void push_back(T&& x);
void pop_back();
template <class... Args> iterator emplace(const_iterator position, Args&&... args);
iterator insert(const_iterator position, const T& x);
iterator insert(const_iterator position, T&& x);
iterator insert(const_iterator position, size_type n, const T& x);
template <class InputIterator>
iterator insert(const_iterator position, InputIterator first,
InputIterator last);
iterator insert(const_iterator position, initializer_list<T> il);
iterator erase(const_iterator position);
iterator erase(const_iterator position, const_iterator last);
void swap(list&);
void clear() noexcept;
// [list.ops], list operations:
void splice(const_iterator position, list& x);
void splice(const_iterator position, list&& x);
void splice(const_iterator position, list& x, const_iterator i);
void splice(const_iterator position, list&& x, const_iterator i);
void splice(const_iterator position, list& x,
const_iterator first, const_iterator last);
void splice(const_iterator position, list&& x,
const_iterator first, const_iterator last);
void remove(const T& value);
template <class Predicate> void remove_if(Predicate pred);
void unique();
template <class BinaryPredicate>
void unique(BinaryPredicate binary_pred);
void merge(list& x);
void merge(list&& x);
template <class Compare> void merge(list& x, Compare comp);
template <class Compare> void merge(list&& x, Compare comp);
void sort();
template <class Compare> void sort(Compare comp);
void reverse() noexcept;
};
template <class T, class Allocator>
bool operator==(const list<T,Allocator>& x, const list<T,Allocator>& y);
template <class T, class Allocator>
bool operator< (const list<T,Allocator>& x, const list<T,Allocator>& y);
template <class T, class Allocator>
bool operator!=(const list<T,Allocator>& x, const list<T,Allocator>& y);
template <class T, class Allocator>
bool operator> (const list<T,Allocator>& x, const list<T,Allocator>& y);
template <class T, class Allocator>
bool operator>=(const list<T,Allocator>& x, const list<T,Allocator>& y);
template <class T, class Allocator>
bool operator<=(const list<T,Allocator>& x, const list<T,Allocator>& y);
// specialized algorithms:
template <class T, class Allocator>
void swap(list<T,Allocator>& x, list<T,Allocator>& y);
}
These member functions are only provided by containers whose iterators are random access iterators.
explicit list(const Allocator& = Allocator());
Effects: Constructs an empty list, using the specified allocator.
Complexity: Constant.
Effects: Constructs a list with n value-initialized elements.
Requires: T shall be DefaultConstructible.
Complexity: Linear in n.
list(size_type n, const T& value,
const Allocator& = Allocator());
Effects: Constructs a list with n copies of value, using the specified allocator.
Requires: T shall be CopyInsertable into *this.
Complexity: Linear in n.
template <class InputIterator>
list(InputIterator first, InputIterator last,
const Allocator& = Allocator());
Effects: Constructs a list equal to the range [first,last).
Complexity: Linear in distance(first, last).
template <class InputIterator>
void assign(InputIterator first, InputIterator last);
Effects: Replaces the contents of the list with the range [first, last).
void assign(size_type n, const T& t);
Effects: Replaces the contents of the list with n copies of t.
Effects: If size() < sz, appends sz - size() value-initialized elements to the sequence. If sz <= size(), equivalent to
list<T>::iterator it = begin(); advance(it, sz); erase(it, end());
Requires: T shall be DefaultConstructible.
void resize(size_type sz, const T& c);
Effects:
if (sz > size())
insert(end(), sz-size(), c);
else if (sz < size()) {
iterator i = begin();
advance(i, sz);
erase(i, end());
}
else
; // do nothing
Requires: T shall be CopyInsertable into *this.
iterator insert(const_iterator position, const T& x);
iterator insert(const_iterator position, T&& x);
iterator insert(const_iterator position, size_type n, const T& x);
template <class InputIterator>
iterator insert(const_iterator position, InputIterator first,
InputIterator last);
iterator insert(const_iterator position, initializer_list<T>);
template <class... Args> void emplace_front(Args&&... args);
template <class... Args> void emplace_back(Args&&... args);
template <class... Args> iterator emplace(const_iterator position, Args&&... args);
void push_front(const T& x);
void push_front(T&& x);
void push_back(const T& x);
void push_back(T&& x);
Remarks: Does not affect the validity of iterators and references. If an exception is thrown there are no effects.
Complexity: Insertion of a single element into a list takes constant time and exactly one call to a constructor of T. Insertion of multiple elements into a list is linear in the number of elements inserted, and the number of calls to the copy constructor or move constructor of T is exactly equal to the number of elements inserted.
iterator erase(const_iterator position);
iterator erase(const_iterator first, const_iterator last);
void pop_front();
void pop_back();
void clear() noexcept;
Effects: Invalidates only the iterators and references to the erased elements.
Throws: Nothing.
Complexity: Erasing a single element is a constant time operation with a single call to the destructor of T. Erasing a range in a list is linear time in the size of the range and the number of calls to the destructor of type T is exactly equal to the size of the range.
Since lists allow fast insertion and erasing from the middle of a list, certain operations are provided specifically for them.266
list provides three splice operations that destructively move elements from one list to another. The behavior of splice operations is undefined if get_allocator() != x.get_allocator().
void splice(const_iterator position, list& x);
void splice(const_iterator position, list&& x);
Requires: &x != this.
Effects: Inserts the contents of x before position and x becomes empty. Pointers and references to the moved elements of x now refer to those same elements but as members of *this. Iterators referring to the moved elements will continue to refer to their elements, but they now behave as iterators into *this, not into x.
Throws: Nothing.
Complexity: Constant time.
void splice(const_iterator position, list& x, const_iterator i);
void splice(const_iterator position, list&& x, const_iterator i);
Effects: Inserts an element pointed to by i from list x before position and removes the element from x. The result is unchanged if position == i or position == ++i. Pointers and references to *i continue to refer to this same element but as a member of *this. Iterators to *i (including i itself) continue to refer to the same element, but now behave as iterators into *this, not into x.
Requires: i is a valid dereferenceable iterator of x.
Throws: Nothing.
Complexity: Constant time.
void splice(const_iterator position, list& x, const_iterator first,
const_iterator last);
void splice(const_iterator position, list&& x, const_iterator first,
const_iterator last);
Effects: Inserts elements in the range [first,last) before position and removes the elements from x.
Requires: [first, last) is a valid range in x. The result is undefined if position is an iterator in the range [first,last). Pointers and references to the moved elements of x now refer to those same elements but as members of *this. Iterators referring to the moved elements will continue to refer to their elements, but they now behave as iterators into *this, not into x.
Throws: Nothing.
Complexity: Constant time if &x == this; otherwise, linear time.
void remove(const T& value);
template <class Predicate> void remove_if(Predicate pred);
Effects: Erases all the elements in the list referred by a list iterator i for which the following conditions hold: *i == value, pred(*i) != false. Invalidates only the iterators and references to the erased elements.
Throws: Nothing unless an exception is thrown by *i == value or pred(*i) != false.
Remarks: Stable.
Complexity: Exactly size() applications of the corresponding predicate.
void unique();
template <class BinaryPredicate> void unique(BinaryPredicate binary_pred);
Effects: Erases all but the first element from every consecutive group of equal elements referred to by the iterator i in the range [first + 1,last) for which *i == *(i-1) (for the version of unique with no arguments) or pred(*i, *(i - 1)) (for the version of unique with a predicate argument) holds. Invalidates only the iterators and references to the erased elements.
Throws: Nothing unless an exception in thrown by *i == *(i-1) or pred(*i, *(i - 1))
Complexity: If the range [first, last) is not empty, exactly (last - first) - 1 applications of the corresponding predicate, otherwise no applications of the predicate.
void merge(list& x);
void merge(list&& x);
template <class Compare> void merge(list& x, Compare comp);
template <class Compare> void merge(list&& x, Compare comp);
Requires: comp shall define a strict weak ordering ([alg.sorting]), and both the list and the argument list shall be sorted according to this ordering.
Effects: If (&x == this) does nothing; otherwise, merges the two sorted ranges [begin(), end()) and [x.begin(), x.end()). The result is a range in which the elements will be sorted in non-decreasing order according to the ordering defined by comp; that is, for every iterator i, in the range other than the first, the condition comp(*i, *(i - 1)) will be false. Pointers and references to the moved elements of x now refer to those same elements but as members of *this. Iterators referring to the moved elements will continue to refer to their elements, but they now behave as iterators into *this, not into x.
Remarks: Stable. If (&x != this) the range [x.begin(), x.end()) is empty after the merge. No elements are copied by this operation. The behavior is undefined if this->get_allocator() != x.get_allocator().
Complexity: At most size() + x.size() - 1 applications of comp if (&x != this); otherwise, no applications of comp are performed. If an exception is thrown other than by a comparison there are no effects.
Effects: Reverses the order of the elements in the list. Does not affect the validity of iterators and references.
Complexity: Linear time.
void sort();
template <class Compare> void sort(Compare comp);
Requires: operator< (for the first version) or comp (for the second version) shall define a strict weak ordering ([alg.sorting]).
Effects: Sorts the list according to the operator< or a Compare function object. Does not affect the validity of iterators and references.
Remarks: Stable.
Complexity: Approximately N log(N) comparisons, where N == size().
As specified in [allocator.requirements], the requirements in this Clause apply only to lists whose allocators compare equal.
template <class T, class Allocator>
void swap(list<T,Allocator>& x, list<T,Allocator>& y);
Effects:
x.swap(y);