23 Containers library [containers]

23.1 General [containers.general]

1

This Clause describes components that C++ programs may use to organize collections of information.

2

The following subclauses describe container requirements, and components for sequence containers and associative containers, as summarized in Table [tab:containers.lib.summary].

Table 95 — Containers library summary
Subclause Header(s)
[container.requirements] Requirements
[sequences] Sequence containers <array>
<deque>
<forward_list>
<list>
<vector>
[associative] Associative containers <map>
<set>
[unord] Unordered associative containers <unordered_map>
<unordered_set>
[container.adaptors] Container adaptors <queue>
<stack>

23.2 Container requirements [container.requirements]

23.2.1 General container requirements [container.requirements.general]

1

Containers are objects that store other objects. They control allocation and deallocation of these objects through constructors, destructors, insert and erase operations.

2

All of the complexity requirements in this Clause are stated solely in terms of the number of operations on the contained objects. [ Example: the copy constructor of type vector <vector<int> > has linear complexity, even though the complexity of copying each contained vector<int> is itself linear.  — end example ]

3

For the components affected by this subclause that declare an allocator_type, objects stored in these components shall be constructed using the allocator_traits<allocator_type>::construct function and destroyed using the allocator_traits<allocator_type>::destroy function ([allocator.traits.members]). These functions are called only for the container's element type, not for internal types used by the container. [ Note: This means, for example, that a node-based container might need to construct nodes containing aligned buffers and call construct to place the element into the buffer.  — end note ]

4

In Tables [tab:containers.container.requirements] and [tab:containers.reversible.requirements], X denotes a container class containing objects of type T, a and b denote values of type X, u denotes an identifier, r denotes a non-const value of type X, and rv denotes a non-const rvalue of type X.

Table 96 — Container requirements
ExpressionReturn typeOperationalAssertion/noteComplexity
semanticspre-/post-condition
X::value_type T Requires: T is Destructible compile time
X::reference lvalue of T compile time
X::const_reference const lvalue of T compile time
X::iterator iterator type whose value type is T any iterator category that meets the forward iterator requirements. convertible to X::const_iterator. compile time
X::const_iterator constant iterator type whose value type is T any iterator category that meets the forward iterator requirements. compile time
X::difference_type signed integer type is identical to the difference type of X::iterator and X::const_iterator compile time
X::size_type unsigned integer type size_type can represent any non-negative value of difference_type compile time
X u; post: u.empty() constant
X() post: X().empty() constant
X(a) Requires: T is CopyInsertable into X (see below).
post: a == X(a). 		linear
X u(a)
X u = a; 		Requires: T is CopyInsertable into X (see below).
post: u == a 		linear
X u(rv)
X u = rv 		post: u shall be equal to the value that rv had before this construction (Note B)
a = rv X& All existing elements of a are either move assigned to or destroyed a shall be equal to the value that rv had before this assignment linear
(&a)->~X() void note: the destructor is applied to every element of a; all the memory is deallocated. linear
a.begin() iterator; const_iterator for constant a constant
a.end() iterator; const_iterator for constant a constant
a.cbegin() const_iterator const_cast<X const&>(a).begin(); constant
a.cend() const_iterator const_cast<X const&>(a).end(); constant
a == b convertible to bool == is an equivalence relation. distance(a.begin(), a.end()) == distance(b.begin(), b.end()) && equal(a.begin(), a.end(), b.begin()) Requires: T is EqualityComparable linear
a != b convertible to bool Equivalent to: !(a == b) linear
a.swap(b) void exchanges the contents of a and b (Note A)
swap(a, b) void a.swap(b) (Note A)
r = a X& post: r == a. linear
a.size() size_type distance(a.begin(), a.end()) constant
a.max_size() size_type distance(begin(), end()) for the largest possible container constant
a.empty() convertible to bool a.begin() == a.end() constant

Notes: the algorithm equal() is defined in Clause [algorithms]. Those entries marked “(Note A)” or “(Note B)” have linear complexity for array and have constant complexity for all other standard containers.

5

The member function size() returns the number of elements in the container. The number of elements is defined by the rules of constructors, inserts, and erases.

6

begin() returns an iterator referring to the first element in the container. end() returns an iterator which is the past-the-end value for the container. If the container is empty, then begin() == end();

7

Unless otherwise specified, all containers defined in this clause obtain memory using an allocator (see [allocator.requirements]). Copy constructors for these container types obtain an allocator by calling allocator_traits<allocator_type>::select_on_container_copy_construction on their first parameters. Move constructors obtain an allocator by move construction from the allocator belonging to the container being moved. Such move construction of the allocator shall not exit via an exception. All other constructors for these container types take an Allocator& argument ([allocator.requirements]), an allocator whose value type is the same as the container's value type. [ Note: If an invocation of a constructor uses the default value of an optional allocator argument, then the Allocator type must support value initialization.  — end note ] A copy of this allocator is used for any memory allocation performed, by these constructors and by all member functions, during the lifetime of each container object or until the allocator is replaced. The allocator may be replaced only via assignment or swap(). Allocator replacement is performed by copy assignment, move assignment, or swapping of the allocator only if allocator_traits<allocator_type>::propagate_on_container_copy_assignment::value, allocator_traits<allocator_type>::propagate_on_container_move_assignment::value, or allocator_traits<allocator_type>::propagate_on_container_swap::value is true within the implementation of the corresponding container operation. The behavior of a call to a container's swap function is undefined unless the objects being swapped have allocators that compare equal or allocator_traits<allocator_type>::propagate_on_container_swap::value is true. In all container types defined in this Clause, the member get_allocator() returns a copy of the allocator used to construct the container or, if that allocator has been replaced, a copy of the most recent replacement.

8

The expression a.swap(b), for containers a and b of a standard container type other than array, shall exchange the values of a and b without invoking any move, copy, or swap operations on the individual container elements. Any Compare, Pred, or Hash objects belonging to a and b shall be swappable and shall be exchanged by unqualified calls to non-member swap. If allocator_traits<allocator_type>::propagate_on_container_swap::value is true, then the allocators of a and b shall also be exchanged using an unqualified call to non-member swap. Otherwise, they shall not be swapped, and the behavior is undefined unless a.get_allocator() == b.get_allocator(). Every iterator referring to an element in one container before the swap shall refer to the same element in the other container after the swap. It is unspecified whether an iterator with value a.end() before the swap will have value b.end() after the swap.

9

If the iterator type of a container belongs to the bidirectional or random access iterator categories ([iterator.requirements]), the container is called reversible and satisfies the additional requirements in Table [tab:containers.reversible.requirements].

Table 97 — Reversible container requirements
ExpressionReturn typeAssertion/noteComplexity
pre-/post-condition
X::reverse_iterator iterator type whose value type is T reverse_iterator<iterator> compile time
X::const_reverse_iterator iterator type whose value type is const T reverse_iterator<const_iterator> compile time
a.rbegin() reverse_iterator; const_reverse_iterator for constant a reverse_iterator(end()) constant
a.rend() reverse_iterator; const_reverse_iterator for constant a reverse_iterator(begin()) constant
a.crbegin(); const_reverse_iterator const_cast<X const&>(a).rbegin(); constant
a.crend(); const_reverse_iterator const_cast<X const&>(a).rend(); constant
10

Unless otherwise specified (see [associative.reqmts.except], [unord.req.except], [deque.modifiers], and [vector.modifiers]) all container types defined in this Clause meet the following additional requirements:

  • (10.1)

    if an exception is thrown by an insert() or emplace() function while inserting a single element, that function has no effects.

  • (10.2)

    if an exception is thrown by a push_back() or push_front() function, that function has no effects.

  • (10.3)

    no erase(), clear(), pop_back() or pop_front() function throws an exception.

  • (10.4)

    no copy constructor or assignment operator of a returned iterator throws an exception.

  • (10.5)

    no swap() function throws an exception.

  • (10.6)

    no swap() function invalidates any references, pointers, or iterators referring to the elements of the containers being swapped. [ Note: The end() iterator does not refer to any element, so it may be invalidated.  — end note ]

11

Unless otherwise specified (either explicitly or by defining a function in terms of other functions), invoking a container member function or passing a container as an argument to a library function shall not invalidate iterators to, or change the values of, objects within that container.

12

Table [tab:containers.optional.operations] lists operations that are provided for some types of containers but not others. Those containers for which the listed operations are provided shall implement the semantics described in Table [tab:containers.optional.operations] unless otherwise stated.

Table 98 — Optional container operations
ExpressionReturn typeOperationalAssertion/noteComplexity
semanticspre-/post-condition
a < b convertible to bool lexicographical_compare( a.begin(), a.end(), b.begin(), b.end()) pre: < is defined for values of T. < is a total ordering relationship. linear
a > b convertible to bool b < a linear
a <= b convertible to bool !(a > b) linear
a >= b convertible to bool !(a < b) linear

Note: the algorithm lexicographical_compare() is defined in Clause [algorithms].

13

All of the containers defined in this Clause and in ([basic.string]) except array meet the additional requirements of an allocator-aware container, as described in Table [tab:containers.allocatoraware].

Given a container type X having an allocator_type identical to A and a value_type identical to T and given an lvalue m of type A, a pointer p of type T*, an expression v of type T, and an rvalue rv of type T, the following terms are defined. (If X is not allocator-aware, the terms below are defined as if A were std::allocator<T>.)

[ Note: A container calls allocator_traits<A>::construct(m, p, args) to construct an element at p using args. The default construct in std::allocator will call ::new((void*)p) T(args), but specialized allocators may choose a different definition.  — end note ]

14

In Table [tab:containers.allocatoraware], X denotes an allocator-aware container class with a value_type of T using allocator of type A, u denotes a variable, a and b denote non-const lvalues of type X, t denotes an lvalue or a const rvalue of type X, rv denotes a non-const rvalue of type X, m is a value of type A, and Q is an allocator type.

Table 99 — Allocator-aware container requirements
ExpressionReturn typeAssertion/noteComplexity
pre-/post-condition
allocator_type A Requires: allocator_type::value_type is the same as X::value_type. compile time
get_- allocator() A constant
X()
X u; 		Requires: A is DefaultConstructible.
post: u.empty() returns true, u.get_allocator() == A() 		constant
X(m) post: u.empty() returns true, constant
X u(m); u.get_allocator() == m
X(t, m)
X u(t, m); 		Requires: T is CopyInsertable into X.
post: u == t, get_allocator() == m 		linear
X(rv)
X u(rv) 		Requires: move construction of A shall not exit via an exception.
post: u shall have the same elements as rv had before this construction; the value of get_allocator() shall be the same as the value of rv.get_allocator() before this construction. 		constant
X(rv, m)
X u(rv, m); 		Requires: T is MoveInsertable into X.
post: u shall have the same elements, or copies of the elements, that rv had before this construction, get_allocator() == m 		constant if m == rv.get_allocator(), otherwise linear
a = t X& Requires: T is CopyInsertable into X and CopyAssignable.
post: a == t 		linear
a = rv X& Requires: If allocator_-
traits<allocator_type>
::propagate_on_container_-
move_assignment::value is
false, T is MoveInsertable into X and MoveAssignable. All existing elements of a are either move assigned to or destroyed.
post: a shall be equal to the value that rv had before this assignment. 		linear
a.swap(b) void exchanges the contents of a and b constant

23.2.2 Container data races [container.requirements.dataraces]

1

For purposes of avoiding data races ([res.on.data.races]), implementations shall consider the following functions to be const: begin, end, rbegin, rend, front, back, data, find, lower_bound, upper_bound, equal_range, at and, except in associative or unordered associative containers, operator[].

2

Notwithstanding ([res.on.data.races]), implementations are required to avoid data races when the contents of the contained object in different elements in the same sequence, excepting vector<bool>, are modified concurrently.

3

[ Note: For a vector<int> x with a size greater than one, x[1] = 5 and *x.begin() = 10 can be executed concurrently without a data race, but x[0] = 5 and *x.begin() = 10 executed concurrently may result in a data race. As an exception to the general rule, for a vector<bool> y, y[0] = true may race with y[1] = true.  — end note ]

23.2.3 Sequence containers [sequence.reqmts]

1

A sequence container organizes a finite set of objects, all of the same type, into a strictly linear arrangement. The library provides four basic kinds of sequence containers: vector, forward_list, list, and deque. In addition, array is provided as a sequence container which provides limited sequence operations because it has a fixed number of elements. The library also provides container adaptors that make it easy to construct abstract data types, such as stacks or queues, out of the basic sequence container kinds (or out of other kinds of sequence containers that the user might define).

2

The sequence containers offer the programmer different complexity trade-offs and should be used accordingly. vector or array is the type of sequence container that should be used by default. list or forward_list should be used when there are frequent insertions and deletions from the middle of the sequence. deque is the data structure of choice when most insertions and deletions take place at the beginning or at the end of the sequence.

3

In Tables [tab:containers.sequence.requirements] and [tab:containers.sequence.optional], X denotes a sequence container class, a denotes a value of X containing elements of type T, A denotes X::allocator_type if it exists and std::allocator<T> if it doesn't, i and j denote iterators satisfying input iterator requirements and refer to elements implicitly convertible to value_type, [i, j) denotes a valid range, il designates an object of type initializer_list<value_type>, n denotes a value of X::size_type, p denotes a valid const iterator to a, q denotes a valid dereferenceable const iterator to a, [q1, q2) denotes a valid range of const iterators in a, t denotes an lvalue or a const rvalue of X::value_type, and rv denotes a non-const rvalue of X::value_type. Args denotes a template parameter pack; args denotes a function parameter pack with the pattern Args&&.

4

The complexities of the expressions are sequence dependent.

Table 100 — Sequence container requirements (in addition to container)
ExpressionReturn typeAssertion/note
pre-/post-condition
X(n, t)
X a(n, t) 		Requires: T shall be CopyInsertable into X.
post: distance(begin(), end()) == n
Constructs a sequence container with n copies of t
X(i, j)
X a(i, j) 		Requires: T shall be EmplaceConstructible into X from *i. For vector, if the iterator does not meet the forward iterator requirements ([forward.iterators]), T shall also be MoveInsertable into X. Each iterator in the range [i,j) shall be dereferenced exactly once.
post: distance(begin(), end()) == distance(i, j)
Constructs a sequence container equal to the range [i, j)
X(il); Equivalent to X(il.begin(), il.end())
a = il; X& Requires: T is CopyInsertable into X and CopyAssignable. Assigns the range [il.begin(),il.end()) into a. All existing elements of a are either assigned to or destroyed.
Returns: *this.
a.emplace(p, args); iterator Requires: T is EmplaceConstructible into X from args. For vector and deque, T is also MoveInsertable into X and MoveAssignable. Effects: Inserts an object of type T constructed with std::forward<Args>(args)... before p.
a.insert(p,t) iterator Requires: T shall be CopyInsertable into X. For vector and deque, T shall also be CopyAssignable.
Effects: Inserts a copy of t before p.
a.insert(p,rv) iterator Requires: T shall be MoveInsertable into X. For vector and deque, T shall also be MoveAssignable.
Effects: Inserts a copy of rv before p.
a.insert(p,n,t) iterator Requires: T shall be CopyInsertable into X and CopyAssignable.
Inserts n copies of t before p.
a.insert(p,i,j) iterator Requires: T shall be EmplaceConstructible into X from *i. For vector, if the iterator does not meet the forward iterator requirements ([forward.iterators]), T shall also be MoveInsertable into X and MoveAssignable. Each iterator in the range [i,j) shall be dereferenced exactly once.
pre: i and j are not iterators into a.
Inserts copies of elements in [i, j) before p
a.insert(p, il); iterator a.insert(p, il.begin(), il.end()).
a.erase(q) iterator Requires: For vector and deque, T shall be MoveAssignable.
Effects: Erases the element pointed to by q
a.erase(q1,q2) iterator Requires: For vector and deque, T shall be MoveAssignable.
Effects: Erases the elements in the range [q1, q2).
a.clear() void Destroys all elements in a. Invalidates all references, pointers, and iterators referring to the elements of a and may invalidate the past-the-end iterator.
post: a.empty() returns true
a.assign(i,j) void Requires: T shall be EmplaceConstructible into X from *i and assignable from *i. For vector, if the iterator does not meet the forward iterator requirements ([forward.iterators]), T shall also be MoveInsertable into X.
Each iterator in the range [i,j) shall be dereferenced exactly once.
pre: i, j are not iterators into a.
Replaces elements in a with a copy of [i, j).
a.assign(il) void a.assign(il.begin(), il.end()).
a.assign(n,t) void Requires: T shall be CopyInsertable into X and CopyAssignable.
pre: t is not a reference into a.
Replaces elements in a with n copies of t.
5

iterator and const_iterator types for sequence containers shall be at least of the forward iterator category.

6

The iterator returned from a.insert(p, t) points to the copy of t inserted into a.

7

The iterator returned from a.insert(p, rv) points to the copy of rv inserted into a.

8

The iterator returned from a.insert(p, n, t) points to the copy of the first element inserted into a, or p if n == 0.

9

The iterator returned from a.insert(p, i, j) points to the copy of the first element inserted into a, or p if i == j.

10

The iterator returned from a.insert(p, i1) points to the copy of the first element inserted into a, or p if i1 is empty.

11

The iterator returned from a.emplace(p, args) points to the new element constructed from args into a.

12

The iterator returned from a.erase(q) points to the element immediately following q prior to the element being erased. If no such element exists, a.end() is returned.

13

The iterator returned by a.erase(q1,q2) points to the element pointed to by q2 prior to any elements being erased. If no such element exists, a.end() is returned.

14

For every sequence container defined in this Clause and in Clause [strings]:

  • (14.1)

    If the constructor

    template <class InputIterator>
X(InputIterator first, InputIterator last,
  const allocator_type& alloc = allocator_type())

    is called with a type InputIterator that does not qualify as an input iterator, then the constructor shall not participate in overload resolution.

  • (14.2)

    If the member functions of the forms:

    template <class InputIterator>          // such as insert()
rt fx1(const_iterator p, InputIterator first, InputIterator last);

template <class InputIterator>          // such as append(), assign()
rt fx2(InputIterator first, InputIterator last);

template <class InputIterator>          // such as replace()
rt fx3(const_iterator i1, const_iterator i2, InputIterator first, InputIterator last);

    are called with a type InputIterator that does not qualify as an input iterator, then these functions shall not participate in overload resolution.

15

The extent to which an implementation determines that a type cannot be an input iterator is unspecified, except that as a minimum integral types shall not qualify as input iterators.

16

Table [tab:containers.sequence.optional] lists operations that are provided for some types of sequence containers but not others. An implementation shall provide these operations for all container types shown in the “container” column, and shall implement them so as to take amortized constant time.

Table 101 — Optional sequence container operations
ExpressionReturn typeOperational semanticsContainer
a.front() reference; const_reference for constant a *a.begin() basic_string, array, deque, forward_list, list, vector
a.back() reference; const_reference for constant a { auto tmp = a.end();
-- tmp;
return *tmp; } 		basic_string, array, deque, list, vector
a.emplace_- front(args) void Prepends an object of type T constructed with std::forward<Args>(args)....
Requires: T shall be EmplaceConstructible into X from args. 		deque, forward_list, list
a.emplace_- back(args) void Appends an object of type T constructed with std::forward<Args>(args)....
Requires: T shall be EmplaceConstructible into X from args. For vector, T shall also be MoveInsertable into X. 		deque, list, vector
a.push_front(t) void Prepends a copy of t.
Requires: T shall be CopyInsertable into X. 		deque, forward_list, list
a.push_front(rv) void Prepends a copy of rv.
Requires: T shall be MoveInsertable into X. 		deque, forward_list, list
a.push_back(t) void Appends a copy of t.
Requires: T shall be CopyInsertable into X. 		basic_string, deque, list, vector
a.push_back(rv) void Appends a copy of rv.
Requires: T shall be MoveInsertable into X. 		basic_string, deque, list, vector
a.pop_front() void Destroys the first element.
Requires: a.empty() shall be false. 		deque, forward_list, list
a.pop_back() void Destroys the last element.
Requires: a.empty() shall be false. 		basic_string, deque, list, vector
a[n] reference; const_reference for constant a *(a.begin() + n) basic_string, array, deque, vector
a.at(n) reference; const_reference for constant a *(a.begin() + n) basic_string, array, deque, vector
17

The member function at() provides bounds-checked access to container elements. at() throws out_of_range if n >= a.size().

23.2.4 Associative containers [associative.reqmts]

1

Associative containers provide fast retrieval of data based on keys. The library provides four basic kinds of associative containers: set, multiset, map and multimap.

2

Each associative container is parameterized on Key and an ordering relation Compare that induces a strict weak ordering ([alg.sorting]) on elements of Key. In addition, map and multimap associate an arbitrary type T with the Key. The object of type Compare is called the comparison object of a container.

3

The phrase “equivalence of keys” means the equivalence relation imposed by the comparison and not the operator== on keys. That is, two keys k1 and k2 are considered to be equivalent if for the comparison object comp, comp(k1, k2) == false && comp(k2, k1) == false. For any two keys k1 and k2 in the same container, calling comp(k1, k2) shall always return the same value.

4

An associative container supports unique keys if it may contain at most one element for each key. Otherwise, it supports equivalent keys. The set and map classes support unique keys; the multiset and multimap classes support equivalent keys. For multiset and multimap, insert, emplace, and erase preserve the relative ordering of equivalent elements.

5

For set and multiset the value type is the same as the key type. For map and multimap it is equal to pair<const Key, T>. Keys in an associative container are immutable.

6

iterator of an associative container is of the bidirectional iterator category. For associative containers where the value type is the same as the key type, both iterator and const_iterator are constant iterators. It is unspecified whether or not iterator and const_iterator are the same type. [ Note: iterator and const_iterator have identical semantics in this case, and iterator is convertible to const_iterator. Users can avoid violating the One Definition Rule by always using const_iterator in their function parameter lists.  — end note ]

7

The associative containers meet all the requirements of Allocator-aware containers ([container.requirements.general]), except that for map and multimap, the requirements placed on value_type in Table [tab:containers.container.requirements] apply instead to key_type and mapped_type. [ Note: For example, in some cases key_type and mapped_type are required to be CopyAssignable even though the associated value_type, pair<const key_type, mapped_type>, is not CopyAssignable.  — end note ]

8

In Table [tab:containers.associative.requirements], X denotes an associative container class, a denotes a value of X, a_uniq denotes a value of X when X supports unique keys, a_eq denotes a value of X when X supports multiple keys, u denotes an identifier, i and j satisfy input iterator requirements and refer to elements implicitly convertible to value_type, [i,j) denotes a valid range, p denotes a valid const iterator to a, q denotes a valid dereferenceable const iterator to a, [q1, q2) denotes a valid range of const iterators in a, il designates an object of type initializer_list<value_type>, t denotes a value of X::value_type, k denotes a value of X::key_type and c denotes a value of type X::key_compare. A denotes the storage allocator used by X, if any, or std::allocator<X::value_type> otherwise, and m denotes an allocator of a type convertible to A.

Table 102 — Associative container requirements (in addition to container)
ExpressionReturn typeAssertion/noteComplexity
pre-/post-condition
X::key_type Key Requires: Key is Destructible. compile time
mapped_type (map and multimap only) T Requires: T is Destructible. compile time
X::key_compare Compare defaults to less<key_type> compile time
X::value_compare a binary predicate type is the same as key_compare for set and multiset; is an ordering relation on pairs induced by the first component (i.e., Key) for map and multimap. compile time
X(c)
X a(c); 		Requires: key_compare is CopyConstructible.
Effects: Constructs an empty container. Uses a copy of c as a comparison object. 		constant
X()
X a; 		Requires: key_compare is DefaultConstructible.
Effects: Constructs an empty container. Uses Compare() as a comparison object 		constant
X(i,j,c)
X a(i,j,c); 		Requires: key_compare is CopyConstructible. value_type is EmplaceConstructible into X from *i.
Effects: Constructs an empty container and inserts elements from the range [i, j) into it; uses c as a comparison object. 		N log N in general (N has the value distance(i, j)); linear if [i, j) is sorted with value_comp()
X(i,j) X a(i,j); Requires: key_compare is DefaultConstructible. value_type is EmplaceConstructible into X from *i.
Effects: Same as above, but uses Compare() as a comparison object 		same as above
X(il); Same as X(il.begin(), il.end()). same as X(il.begin(), il.end()).
a = il X& Requires: value_type is CopyInsertable into X and CopyAssignable.
Effects: Assigns the range [il.begin(),il.end()) into a. All existing elements of a are either assigned to or destroyed. 		N log N in general (where N has the value il.size() + a.size()); linear if [il.begin(),il.end()) is sorted with value_comp().
a.key_comp() X::key_compare returns the comparison object out of which a was constructed. constant
a.value_comp() X::value_compare returns an object of value_compare constructed out of the comparison object constant
a_uniq. emplace(args) pair<iterator, bool> Requires: value_type shall be EmplaceConstructible into X from args.
Effects: Inserts a value_type object t constructed with std::forward<Args>(args)... if and only if there is no element in the container with key equivalent to the key of t. The bool component of the returned pair is true if and only if the insertion takes place, and the iterator component of the pair points to the element with key equivalent to the key of t. 		logarithmic
a_eq. emplace(args) iterator Requires: value_type shall be EmplaceConstructible into X from args.
Effects: Inserts a value_type object t constructed with std::forward<Args>(args)... and returns the iterator pointing to the newly inserted element. If a range containing elements equivalent to t exists in a_eq, t is inserted at the end of that range. 		logarithmic
a.emplace_hint(p, args) iterator equivalent to a.emplace( std::forward<Args>(args)...). Return value is an iterator pointing to the element with the key equivalent to the newly inserted element. The element is inserted as close as possible to the position just prior to p. logarithmic in general, but amortized constant if the element is inserted right before p
a_uniq. insert(t) pair<iterator, bool> Requires: If t is a non-const rvalue expression, value_type shall be MoveInsertable into X; otherwise, value_type shall be CopyInsertable into X.
Effects: Inserts t if and only if there is no element in the container with key equivalent to the key of t. The bool component of the returned pair is true if and only if the insertion takes place, and the iterator component of the pair points to the element with key equivalent to the key of t. 		logarithmic
a_eq.insert(t) iterator Requires: If t is a non-const rvalue expression, value_type shall be MoveInsertable into X; otherwise, value_type shall be CopyInsertable into X.
Effects: Inserts t and returns the iterator pointing to the newly inserted element. If a range containing elements equivalent to t exists in a_eq, t is inserted at the end of that range. 		logarithmic
a.insert(
p, t) 		iterator Requires: If t is a non-const rvalue expression, value_type shall be MoveInsertable into X; otherwise, value_type shall be CopyInsertable into X.
Effects: Inserts t if and only if there is no element with key equivalent to the key of t in containers with unique keys; always inserts t in containers with equivalent keys. always returns the iterator pointing to the element with key equivalent to the key of t. t is inserted as close as possible to the position just prior to p.		 logarithmic in general, but amortized constant if t is inserted right before p.
a.insert(
i, j) 		void Requires: value_type shall be EmplaceConstructible into X from *i.
pre: i, j are not iterators into a. inserts each element from the range [i,j) if and only if there is no element with key equivalent to the key of that element in containers with unique keys; always inserts that element in containers with equivalent keys. 		Nlog (a.size() + N) (N has the value distance(i, j)
a.insert(il) void Equivalent to a.insert(il.begin(), il.end()).
a.erase(k) size_type erases all elements in the container with key equivalent to k. returns the number of erased elements. log (a.size()) + a.count(k)
a.erase(q) iterator erases the element pointed to by q. Returns an iterator pointing to the element immediately following q prior to the element being erased. If no such element exists, returns a.end(). amortized constant
a.erase(
q1, q2) 		iterator erases all the elements in the range [q1,q2). Returns q2. log (a.size()) + N where N has the value distance(q1, q2).
a.clear() void a.erase(a.begin(),a.end())
post: a.empty() returns true 		linear in a.size().
a.find(k) iterator; const_iterator for constant a. returns an iterator pointing to an element with the key equivalent to k, or a.end() if such an element is not found logarithmic
a.count(k) size_type returns the number of elements with key equivalent to k log (a.size()) + a.count(k)
a.lower_bound(k) iterator; const_iterator for constant a. returns an iterator pointing to the first element with key not less than k, or a.end() if such an element is not found. logarithmic
a.upper_bound(k) iterator; const_iterator for constant a. returns an iterator pointing to the first element with key greater than k, or a.end() if such an element is not found. logarithmic
a.equal_range(k) pair<iterator, iterator>; pair<const_iterator, const_iterator> for constant a. equivalent to make_pair(a.lower_bound(k), a.upper_bound(k)). logarithmic
9

The insert and emplace members shall not affect the validity of iterators and references to the container, and the erase members shall invalidate only iterators and references to the erased elements.

10

The fundamental property of iterators of associative containers is that they iterate through the containers in the non-descending order of keys where non-descending is defined by the comparison that was used to construct them. For any two dereferenceable iterators i and j such that distance from i to j is positive,

value_comp(*j, *i) == false
11

For associative containers with unique keys the stronger condition holds,

value_comp(*i, *j) != false.
12

When an associative container is constructed by passing a comparison object the container shall not store a pointer or reference to the passed object, even if that object is passed by reference. When an associative container is copied, either through a copy constructor or an assignment operator, the target container shall then use the comparison object from the container being copied, as if that comparison object had been passed to the target container in its constructor.

23.2.4.1 Exception safety guarantees [associative.reqmts.except]

1

For associative containers, no clear() function throws an exception. erase(k) does not throw an exception unless that exception is thrown by the container's Compare object (if any).

2

For associative containers, if an exception is thrown by any operation from within an insert or emplace function inserting a single element, the insertion has no effect.

3

For associative containers, no swap function throws an exception unless that exception is thrown by the swap of the container's Compare object (if any).

23.2.5 Unordered associative containers [unord.req]

1

Unordered associative containers provide an ability for fast retrieval of data based on keys. The worst-case complexity for most operations is linear, but the average case is much faster. The library provides four unordered associative containers: unordered_set, unordered_map, unordered_multiset, and unordered_multimap.

2

Unordered associative containers conform to the requirements for Containers ([container.requirements]), except that the expressions a == b and a != b have different semantics than for the other container types.

3

Each unordered associative container is parameterized by Key, by a function object type Hash that meets the Hash requirements ([hash.requirements]) and acts as a hash function for argument values of type Key, and by a binary predicate Pred that induces an equivalence relation on values of type Key. Additionally, unordered_map and unordered_multimap associate an arbitrary mapped type T with the Key.

4

A hash function is a function object that takes a single argument of type Key and returns a value of type std::size_t.

5

Two values k1 and k2 of type Key are considered equivalent if the container's key_equal function object returns true when passed those values. If k1 and k2 are equivalent, the hash function shall return the same value for both. [ Note: Thus, when an unordered associative container is instantiated with a non-default Pred parameter it usually needs a non-default Hash parameter as well.  — end note ]

6

An unordered associative container supports unique keys if it may contain at most one element for each key. Otherwise, it supports equivalent keys. unordered_set and unordered_map support unique keys. unordered_multiset and unordered_multimap support equivalent keys. In containers that support equivalent keys, elements with equivalent keys are adjacent to each other in the iteration order of the container. Thus, although the absolute order of elements in an unordered container is not specified, its elements are grouped into equivalent-key groups such that all elements of each group have equivalent keys. Mutating operations on unordered containers shall preserve the relative order of elements within each equivalent-key group unless otherwise specified.

7

For unordered_set and unordered_multiset the value type is the same as the key type. For unordered_map and unordered_multimap it is std::pair<const Key, T>.

8

The elements of an unordered associative container are organized into buckets. Keys with the same hash code appear in the same bucket. The number of buckets is automatically increased as elements are added to an unordered associative container, so that the average number of elements per bucket is kept below a bound. Rehashing invalidates iterators, changes ordering between elements, and changes which buckets elements appear in, but does not invalidate pointers or references to elements. For unordered_multiset and unordered_multimap, rehashing preserves the relative ordering of equivalent elements.

9

The unordered associative containers meet all the requirements of Allocator-aware containers ([container.requirements.general]), except that for unordered_map and unordered_multimap, the requirements placed on value_type in Table [tab:containers.container.requirements] apply instead to key_type and mapped_type. [ Note: For example, key_type and mapped_type are sometimes required to be CopyAssignable even though the associated value_type, pair<const key_type, mapped_type>, is not CopyAssignable.  — end note ]

10

In table [tab:HashRequirements]: X is an unordered associative container class, a is an object of type X, b is a possibly const object of type X, a_uniq is an object of type X when X supports unique keys, a_eq is an object of type X when X supports equivalent keys, i and j are input iterators that refer to value_type, [i, j) is a valid range, p and q2 are valid const iterators to a, q and q1 are valid dereferenceable const iterators to a, [q1, q2) is a valid range in a, il designates an object of type initializer_list<value_type>, t is a value of type X::value_type, k is a value of type key_type, hf is a possibly const value of type hasher, eq is a possibly const value of type key_equal, n is a value of type size_type, and z is a value of type float.

Table 103 — Unordered associative container requirements (in addition to container)
ExpressionReturn typeAssertion/note pre-/post-conditionComplexity
X::key_type Key Requires: Key shall be Destructible. compile time
X::mapped_type (unordered_map and unordered_multimap only) T Requires: T is Destructible. compile time
X::hasher Hash Hash shall be a unary function object type such that the expression hf(k) has type std::size_t. compile time
X::key_equal Pred Pred shall be a binary predicate that takes two arguments of type Key. Pred is an equivalence relation. compile time
X::local_iterator An iterator type whose category, value type, difference type, and pointer and reference types are the same as X::iterator's. A local_iterator object may be used to iterate through a single bucket, but may not be used to iterate across buckets. compile time
X::const_local_iterator An iterator type whose category, value type, difference type, and pointer and reference types are the same as X::const_iterator's. A const_local_iterator object may be used to iterate through a single bucket, but may not be used to iterate across buckets. compile time
X(n, hf, eq)
X a(n, hf, eq) 		X Requires: hasher and key_equal are CopyConstructible.
Effects: Constructs an empty container with at least n buckets, using hf as the hash function and eq as the key equality predicate. 		Ο(n)
X(n, hf)
X a(n, hf) 		X Requires: hasher is CopyConstructible and key_equal is DefaultConstructible.
Effects: Constructs an empty container with at least n buckets, using hf as the hash function and key_equal() as the key equality predicate. 		Ο(n)
X(n)
X a(n) 		X Requires: hasher and key_equal are DefaultConstructible.
Effects: Constructs an empty container with at least n buckets, using hasher() as the hash function and key_equal() as the key equality predicate. 		Ο(n)
X()
X a 		X Requires: hasher and key_equal are DefaultConstructible.
Effects: Constructs an empty container with an unspecified number of buckets, using hasher() as the hash function and key_equal() as the key equality predicate. 		constant
X(i, j, n, hf, eq)
X a(i, j, n, hf, eq) 		X Requires: hasher and key_equal are CopyConstructible. value_type is EmplaceConstructible into X from *i.
Effects: Constructs an empty container with at least n buckets, using hf as the hash function and eq as the key equality predicate, and inserts elements from [i, j) into it. 		Average case Ο(N) (N is distance(i, j)), worst case Ο(N2)
X(i, j, n, hf)
X a(i, j, n, hf) 		X Requires: hasher is CopyConstructible and key_equal is DefaultConstructible. value_type is EmplaceConstructible into X from *i.
Effects: Constructs an empty container with at least n buckets, using hf as the hash function and key_equal() as the key equality predicate, and inserts elements from [i, j) into it. 		Average case Ο(N) (N is distance(i, j)), worst case Ο(N2)
X(i, j, n)
X a(i, j, n) 		X Requires: hasher and key_equal are DefaultConstructible. value_type is EmplaceConstructible into X from *i.
Effects: Constructs an empty container with at least n buckets, using hasher() as the hash function and key_equal() as the key equality predicate, and inserts elements from [i, j) into it. 		Average case Ο(N) (N is distance(i, j)), worst case Ο(N2)
X(i, j)
X a(i, j) 		X Requires: hasher and key_equal are DefaultConstructible. value_type is EmplaceConstructible into X from *i.
Effects: Constructs an empty container with an unspecified number of buckets, using hasher() as the hash function and key_equal() as the key equality predicate, and inserts elements from [i, j) into it. 		Average case Ο(N) (N is distance(i, j)), worst case Ο(N2)
X(il) X Same as X(il.begin(), il.end()). Same as X(il.begin(), il.end()).
X(b)
X a(b) 		X Copy constructor. In addition to the requirements of Table [tab:containers.container.requirements], copies the hash function, predicate, and maximum load factor. Average case linear in b.size(), worst case quadratic.
a = b X& Copy assignment operator. In addition to the requirements of Table [tab:containers.container.requirements], copies the hash function, predicate, and maximum load factor. Average case linear in b.size(), worst case quadratic.
a = il X& Requires: value_type is CopyInsertable into X and CopyAssignable.
Effects: Assigns the range [il.begin(),il.end()) into a. All existing elements of a are either assigned to or destroyed. 		Same as a = X(il).
b.hash_function() hasher Returns b's hash function. constant
b.key_eq() key_equal Returns b's key equality predicate. constant
a_uniq. emplace(args) pair<iterator, bool> Requires: value_type shall be EmplaceConstructible into X from args.
Effects: Inserts a value_type object t constructed with std::forward<Args>(args)... if and only if there is no element in the container with key equivalent to the key of t. The bool component of the returned pair is true if and only if the insertion takes place, and the iterator component of the pair points to the element with key equivalent to the key of t. 		Average case Ο(1), worst case Ο(a_uniq.
size()).
a_eq.emplace(args) iterator Requires: value_type shall be EmplaceConstructible into X from args.
Effects: Inserts a value_type object t constructed with std::forward<Args>(args)... and returns the iterator pointing to the newly inserted element. 		Average case Ο(1), worst case Ο(a_eq.
size()).
a.emplace_hint(p, args) iterator Requires: value_type shall be EmplaceConstructible into X from args.
Effects: Equivalent to a.emplace( std::forward<Args>(args)...). Return value is an iterator pointing to the element with the key equivalent to the newly inserted element. The const_iterator p is a hint pointing to where the search should start. Implementations are permitted to ignore the hint. 		Average case Ο(1), worst case Ο(a. size()).
a_uniq.insert(t) pair<iterator, bool> Requires: If t is a non-const rvalue expression, value_type shall be MoveInsertable into X; otherwise, value_type shall be CopyInsertable into X.
Effects: Inserts t if and only if there is no element in the container with key equivalent to the key of t. The bool component of the returned pair indicates whether the insertion takes place, and the iterator component points to the element with key equivalent to the key of t. 		Average case Ο(1), worst case Ο(a_uniq.
size()).
a_eq.insert(t) iterator Requires: If t is a non-const rvalue expression, value_type shall be MoveInsertable into X; otherwise, value_type shall be CopyInsertable into X.
Effects: Inserts t, and returns an iterator pointing to the newly inserted element. 		Average case Ο(1), worst case Ο(a_eq.
size()).
a.insert(q, t) iterator Requires: If t is a non-const rvalue expression, value_type shall be MoveInsertable into X; otherwise, value_type shall be CopyInsertable into X.
Effects: Equivalent to a.insert(t). Return value is an iterator pointing to the element with the key equivalent to that of t. The iterator q is a hint pointing to where the search should start. Implementations are permitted to ignore the hint. 		Average case Ο(1), worst case Ο(a.size()).
a.insert(i, j) void Requires: value_type shall be EmplaceConstructible into X from *i.
Pre: i and j are not iterators in a. Equivalent to a.insert(t) for each element in [i,j). 		Average case Ο(N), where N is distance(i, j). Worst case Ο(N * (a.size())
+ N).
a.insert(il) void Same as a.insert(il.begin(), il.end()). Same as a.insert( il.begin(), il.end()).
a.erase(k) size_type Erases all elements with key equivalent to k. Returns the number of elements erased. Average case Ο(a.count(k)). Worst case Ο(a.size()).
a.erase(q) iterator Erases the element pointed to by q. Return value is the iterator immediately following q prior to the erasure. Average case Ο(1), worst case Ο(a.size()).
a.erase(q1, q2) iterator Erases all elements in the range [q1, q2). Return value is the iterator immediately following the erased elements prior to the erasure. Average case linear in distance(q1, q2), worst case Ο(a.size()).
a.clear() void Erases all elements in the container. Post: a.empty() returns true Linear.
b.find(k) iterator;
const_iterator for const b. 		Returns an iterator pointing to an element with key equivalent to k, or b.end() if no such element exists. Average case Ο(1), worst case Ο(b.size()).
b.count(k) size_type Returns the number of elements with key equivalent to k. Average case Ο(1), worst case Ο(b.size()).
b.equal_range(k) pair<iterator, iterator>;
pair<const_iterator, const_iterator> for const b. 		Returns a range containing all elements with keys equivalent to k. Returns make_pair(b.end(), b.end()) if no such elements exist. Average case Ο(b.count(k)). Worst case Ο(b.size()).
b.bucket_count() size_type Returns the number of buckets that b contains. Constant
b.max_bucket_count() size_type Returns an upper bound on the number of buckets that b might ever contain. Constant
b.bucket(k) size_type Pre: b.bucket_count() > 0.
Returns the index of the bucket in which elements with keys equivalent to k would be found, if any such element existed. Post: the return value shall be in the range [0, b.bucket_count()). 		Constant
b.bucket_size(n) size_type Pre: n shall be in the range [0, b.bucket_count()). Returns the number of elements in the n th bucket. Ο(b.bucket_size(n))
b.begin(n) local_iterator;
const_local_iterator for const b. 		Pre: n shall be in the range [0, b.bucket_count()). b.begin(n) returns an iterator referring to the first element in the bucket. If the bucket is empty, then b.begin(n) == b.end(n). Constant
b.end(n) local_iterator;
const_local_iterator for const b. 		Pre: n shall be in the range [0, b.bucket_count()). b.end(n) returns an iterator which is the past-the-end value for the bucket. Constant
b.cbegin(n) const_local_iterator Pre: n shall be in the range [0, b.bucket_count()). Note: [b.cbegin(n), b.cend(n)) is a valid range containing all of the elements in the n th bucket. Constant
b.cend(n) const_local_iterator Pre: n shall be in the range [0, b.bucket_count()). Constant
b.load_factor() float Returns the average number of elements per bucket. Constant
b.max_load_factor() float Returns a positive number that the container attempts to keep the load factor less than or equal to. The container automatically increases the number of buckets as necessary to keep the load factor below this number. Constant
a.max_load_factor(z) void Pre: z shall be positive. May change the container's maximum load load factor, using z as a hint. Constant
a.rehash(n) void Post: a.bucket_count() > a.size() / a.max_load_factor() and a.bucket_count() >= n. Average case linear in a.size(), worst case quadratic.
a.reserve(n) void Same as a.rehash(ceil(n / a.max_load_factor())). Average case linear in a.size(), worst case quadratic.
11

Two unordered containers a and b compare equal if a.size() == b.size() and, for every equivalent-key group [Ea1,Ea2) obtained from a.equal_range(Ea1), there exists an equivalent-key group [Eb1,Eb2) obtained from b.equal_range(Ea1), such that distance(Ea1, Ea2) == distance(Eb1, Eb2) and is_permutation(Ea1, Ea2, Eb1) returns true. For unordered_set and unordered_map, the complexity of operator== (i.e., the number of calls to the == operator of the value_type, to the predicate returned by key_equal(), and to the hasher returned by hash_function()) is proportional to N in the average case and to N2 in the worst case, where N is a.size(). For unordered_multiset and unordered_multimap, the complexity of operator== is proportional to $\sum E_i^2$ in the average case and to N2 in the worst case, where N is a.size(), and Ei is the size of the ith equivalent-key group in a. However, if the respective elements of each corresponding pair of equivalent-key groups Eai and Ebi are arranged in the same order (as is commonly the case, e.g., if a and b are unmodified copies of the same container), then the average-case complexity for unordered_multiset and unordered_multimap becomes proportional to N (but worst-case complexity remains Ο(N2), e.g., for a pathologically bad hash function). The behavior of a program that uses operator== or operator!= on unordered containers is undefined unless the Hash and Pred function objects respectively have the same behavior for both containers and the equality comparison operator for Key is a refinement264 of the partition into equivalent-key groups produced by Pred.

12

The iterator types iterator and const_iterator of an unordered associative container are of at least the forward iterator category. For unordered associative containers where the key type and value type are the same, both iterator and const_iterator are const iterators.

13

The insert and emplace members shall not affect the validity of references to container elements, but may invalidate all iterators to the container. The erase members shall invalidate only iterators and references to the erased elements.

14

The insert and emplace members shall not affect the validity of iterators if (N+n) < z * B, where N is the number of elements in the container prior to the insert operation, n is the number of elements inserted, B is the container's bucket count, and z is the container's maximum load factor.

263)

Equality comparison is a refinement of partitioning if no two objects that compare equal fall into different partitions.

23.2.5.1 Exception safety guarantees [unord.req.except]

1

For unordered associative containers, no clear() function throws an exception. erase(k) does not throw an exception unless that exception is thrown by the container's Hash or Pred object (if any).

2

For unordered associative containers, if an exception is thrown by any operation other than the container's hash function from within an insert or emplace function inserting a single element, the insertion has no effect.

3

For unordered associative containers, no swap function throws an exception unless that exception is thrown by the swap of the container's Hash or Pred object (if any).

4

For unordered associative containers, if an exception is thrown from within a rehash() function other than by the container's hash function or comparison function, the rehash() function has no effect.

23.3 Sequence containers [sequences]

23.3.1 In general [sequences.general]

1

The headers <array>, <deque>, <forward_list>, <list>, and <vector> define template classes that meet the requirements for sequence containers.

2

The headers <queue> and <stack> define container adaptors ([container.adaptors]) that also meet the requirements for sequence containers.

Header <array> synopsis

#include <initializer_list>

namespace std {
  template <class T, size_t N > struct array;
  template <class T, size_t N>
    bool operator==(const array<T,N>& x, const array<T,N>& y);
  template <class T, size_t N>
    bool operator!=(const array<T,N>& x, const array<T,N>& y);
  template <class T, size_t N>
    bool operator<(const array<T,N>& x, const array<T,N>& y);
  template <class T, size_t N>
    bool operator>(const array<T,N>& x, const array<T,N>& y);
  template <class T, size_t N>
    bool operator<=(const array<T,N>& x, const array<T,N>& y);
  template <class T, size_t N>
    bool operator>=(const array<T,N>& x, const array<T,N>& y);
  template <class T, size_t N >
    void swap(array<T,N>& x, array<T,N>& y) noexcept(noexcept(x.swap(y)));

  template <class T> class tuple_size;
  template <size_t I, class T> class tuple_element;
  template <class T, size_t N>
    struct tuple_size<array<T, N> >;
  template <size_t I, class T, size_t N>
    struct tuple_element<I, array<T, N> >;
  template <size_t I, class T, size_t N>
    T& get(array<T, N>&) noexcept;
  template <size_t I, class T, size_t N>
    T&& get(array<T, N>&&) noexcept;
  template <size_t I, class T, size_t N>
    const T& get(const array<T, N>&) noexcept;
}

Header <deque> synopsis

#include <initializer_list>

namespace std {
  template <class T, class Allocator = allocator<T> > class deque;
  template <class T, class Allocator>
    bool operator==(const deque<T,Allocator>& x, const deque<T,Allocator>& y);
  template <class T, class Allocator>
    bool operator<(const deque<T,Allocator>& x, const deque<T,Allocator>& y);
  template <class T, class Allocator>
    bool operator!=(const deque<T,Allocator>& x, const deque<T,Allocator>& y);
  template <class T, class Allocator>
    bool operator>(const deque<T,Allocator>& x, const deque<T,Allocator>& y);
  template <class T, class Allocator>
    bool operator>=(const deque<T,Allocator>& x, const deque<T,Allocator>& y);
  template <class T, class Allocator>
    bool operator<=(const deque<T,Allocator>& x, const deque<T,Allocator>& y);
  template <class T, class Allocator>
    void swap(deque<T,Allocator>& x, deque<T,Allocator>& y);
}

Header <forward_list> synopsis

#include <initializer_list>

namespace std {
  template <class T, class Allocator = allocator<T> > class forward_list;
  template <class T, class Allocator>
    bool operator==(const forward_list<T,Allocator>& x, const forward_list<T,Allocator>& y);
  template <class T, class Allocator>
    bool operator< (const forward_list<T,Allocator>& x, const forward_list<T,Allocator>& y);
  template <class T, class Allocator>
    bool operator!=(const forward_list<T,Allocator>& x, const forward_list<T,Allocator>& y);
  template <class T, class Allocator>
    bool operator> (const forward_list<T,Allocator>& x, const forward_list<T,Allocator>& y);
  template <class T, class Allocator>
    bool operator>=(const forward_list<T,Allocator>& x, const forward_list<T,Allocator>& y);
  template <class T, class Allocator>
    bool operator<=(const forward_list<T,Allocator>& x, const forward_list<T,Allocator>& y);
  template <class T, class Allocator>
    void swap(forward_list<T,Allocator>& x, forward_list<T,Allocator>& y);
}

Header <list> synopsis

#include <initializer_list>

namespace std {
  template <class T, class Allocator = allocator<T> > class list;
  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);
  template <class T, class Allocator>
    void swap(list<T,Allocator>& x, list<T,Allocator>& y);
}

Header <vector> synopsis

#include <initializer_list>

namespace std {
  template <class T, class Allocator = allocator<T> > class vector;
  template <class T, class Allocator>
    bool operator==(const vector<T,Allocator>& x,const vector<T,Allocator>& y);
  template <class T, class Allocator>
    bool operator< (const vector<T,Allocator>& x,const vector<T,Allocator>& y);
  template <class T, class Allocator>
    bool operator!=(const vector<T,Allocator>& x,const vector<T,Allocator>& y);
  template <class T, class Allocator>
    bool operator> (const vector<T,Allocator>& x,const vector<T,Allocator>& y);
  template <class T, class Allocator>
    bool operator>=(const vector<T,Allocator>& x,const vector<T,Allocator>& y);
  template <class T, class Allocator>
    bool operator<=(const vector<T,Allocator>& x,const vector<T,Allocator>& y);
  template <class T, class Allocator>
    void swap(vector<T,Allocator>& x, vector<T,Allocator>& y);

  template <class Allocator> class vector<bool,Allocator>;

  // hash support
  template <class T> struct hash;
  template <class Allocator> struct hash<vector<bool, Allocator> >;
}

23.3.2 Class template array [array]

23.3.2.1 Class template array overview [array.overview]

1

The header <array> defines a class template for storing fixed-size sequences of objects. An array supports random access iterators. An instance of array<T, N> stores N elements of type T, so that size() == N is an invariant. The elements of an array are stored contiguously, meaning that if a is an array<T, N> then it obeys the identity &a[n] == &a[0] + n for all 0 <= n < N.

2

An array is an aggregate ([dcl.init.aggr]) that can be initialized with the syntax 

array<T, N> a = { initializer-list };

where initializer-list is a comma-separated list of up to N elements whose types are convertible to T.

3

An array satisfies all of the requirements of a container and of a reversible container ([container.requirements]), except that a default constructed array object is not empty and that swap does not have constant complexity. An array satisfies some of the requirements of a sequence container ([sequence.reqmts]). Descriptions are provided here only for operations on array that are not described in one of these tables and for operations where there is additional semantic information.

namespace std {
  template <class T, size_t N >
  struct array {
    //  types:
    typedef T&                                    reference;
    typedef const T&                              const_reference;
    typedef implementation-defined                iterator;
    typedef implementation-defined                const_iterator;
    typedef size_t                                size_type;
    typedef ptrdiff_t                             difference_type;
    typedef T                                     value_type;
    typedef T*                                    pointer;
    typedef const T*                              const_pointer;
    typedef reverse_iterator<iterator>            reverse_iterator;
    typedef reverse_iterator<const_iterator>      const_reverse_iterator;

    T       elems[N];           // exposition only

    // no explicit construct/copy/destroy for aggregate type

    void fill(const T& u);
    void swap(array&) noexcept(noexcept(swap(declval<T&>(), declval<T&>())));

    // 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;

    // capacity:
    constexpr size_type size() noexcept;
    constexpr size_type max_size() noexcept;
    constexpr bool      empty() noexcept;

    // element access:
    reference       operator[](size_type n);
    const_reference operator[](size_type n) const;
    const_reference at(size_type n) const;
    reference       at(size_type n);
    reference       front();
    const_reference front() const;
    reference       back();
    const_reference back() const;

    T *       data() noexcept;
    const T * data() const noexcept;
  };
}
4

[ Note: The member variable elems is shown for exposition only, to emphasize that array is a class aggregate. The name elems is not part of array's interface.  — end note ]

23.3.2.2 array constructors, copy, and assignment [array.cons]

1

The conditions for an aggregate ([dcl.init.aggr]) shall be met. Class array relies on the implicitly-declared special member functions ([class.ctor], [class.dtor], and [class.copy]) to conform to the container requirements table in [container.requirements]. In addition to the requirements specified in the container requirements table, the implicit move constructor and move assignment operator for array require that T be MoveConstructible or MoveAssignable, respectively.

23.3.2.3 array specialized algorithms [array.special]

template <class T, size_t N> void swap(array<T,N>& x, array<T,N>& y) noexcept(noexcept(x.swap(y)));

1

Effects: 

x.swap(y);
2

Complexity: linear in N.

23.3.2.4 array::size [array.size]

template <class T, size_t N> constexpr size_type array<T,N>::size() noexcept;

1

Returns: N

23.3.2.5 array::data [array.data]

T *data() noexcept; const T *data() const noexcept;

1

Returns: elems.

23.3.2.6 array::fill [array.fill]

void fill(const T& u);

1

Effects: fill_n(begin(), N, u)

23.3.2.7 array::swap [array.swap]

void swap(array& y) noexcept(noexcept(swap(declval<T&>(), declval<T&>())));

1

Effects: swap_ranges(begin(), end(), y.begin())

2

Throws: Nothing unless one of the element-wise swap calls throws an exception.

3

Note: Unlike the swap function for other containers, array::swap takes linear time, may exit via an exception, and does not cause iterators to become associated with the other container.

23.3.2.8 Zero sized arrays [array.zero]

1

array shall provide support for the special case N == 0.

2

In the case that N == 0, begin() == end() == unique value. The return value of data() is unspecified.

3

The effect of calling front() or back() for a zero-sized array is undefined.

4

Member function swap() shall have a noexcept-specification which is equivalent to noexcept(true).

23.3.2.9 Tuple interface to class template array [array.tuple]

tuple_size<array<T, N> >::value

1

Return type: integral constant expression.

2

Value: N

tuple_element<I, array<T, N> >::type

3

Requires: I < N. The program is ill-formed if I is out of bounds.

4

Value: The type T.

template <size_t I, class T, size_t N> T& get(array<T, N>& a) noexcept;

5

Requires: I < N. The program is ill-formed if I is out of bounds.

6

Returns: A reference to the Ith element of a, where indexing is zero-based.

template <size_t I, class T, size_t N> T&& get(array<T, N>&& a) noexcept;

7

Effects: Equivalent to return std::move(get<I>(a));

template <size_t I, class T, size_t N> const T& get(const array<T, N>& a) noexcept;

8

Requires: I < N. The program is ill-formed if I is out of bounds.

9

Returns: A const reference to the Ith element of a, where indexing is zero-based.

23.3.3 Class template deque [deque]

23.3.3.1 Class template deque overview [deque.overview]

1

A deque is a sequence container that, like a vector ([vector]), supports random access iterators. In addition, it supports constant time insert and erase operations at the beginning or the end; insert and erase in the middle take linear time. That is, a deque is especially optimized for pushing and popping elements at the beginning and end. As with vectors, storage management is handled automatically.

2

A deque satisfies all of the requirements of a container, of a reversible container (given in tables in [container.requirements]), of a sequence container, including the optional sequence container requirements ([sequence.reqmts]), and of an allocator-aware container (Table [tab:containers.allocatoraware]). Descriptions are provided here only for operations on deque 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 deque {
  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;

    // [deque.cons], construct/copy/destroy:
    explicit deque(const Allocator& = Allocator());
    explicit deque(size_type n);
    deque(size_type n, const T& value,const Allocator& = Allocator());
    template <class InputIterator>
      deque(InputIterator first, InputIterator last,const Allocator& = Allocator());
    deque(const deque& x);
    deque(deque&&);
    deque(const deque&, const Allocator&);
    deque(deque&&, const Allocator&);
    deque(initializer_list<T>, const Allocator& = Allocator());

    ~deque();
    deque& operator=(const deque& x);
    deque& operator=(deque&& x);
    deque& 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;

    // [deque.capacity], capacity:
    size_type size() const noexcept;
    size_type max_size() const noexcept;
    void      resize(size_type sz);
    void      resize(size_type sz, const T& c);
    void      shrink_to_fit();
    bool      empty() const noexcept;

    // element access:
    reference       operator[](size_type n);
    const_reference operator[](size_type n) const;
    reference       at(size_type n);
    const_reference at(size_type n) const;
    reference       front();
    const_reference front() const;
    reference       back();
    const_reference back() const;

    // [deque.modifiers], modifiers:
    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);

    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>);

    void pop_front();
    void pop_back();

    iterator erase(const_iterator position);
    iterator erase(const_iterator first, const_iterator last);
    void     swap(deque&);
    void     clear() noexcept;
  };

  template <class T, class Allocator>
    bool operator==(const deque<T,Allocator>& x, const deque<T,Allocator>& y);
  template <class T, class Allocator>
    bool operator< (const deque<T,Allocator>& x, const deque<T,Allocator>& y);
  template <class T, class Allocator>
    bool operator!=(const deque<T,Allocator>& x, const deque<T,Allocator>& y);
  template <class T, class Allocator>
    bool operator> (const deque<T,Allocator>& x, const deque<T,Allocator>& y);
  template <class T, class Allocator>
    bool operator>=(const deque<T,Allocator>& x, const deque<T,Allocator>& y);
  template <class T, class Allocator>
    bool operator<=(const deque<T,Allocator>& x, const deque<T,Allocator>& y);

  // specialized algorithms:
  template <class T, class Allocator>
    void swap(deque<T,Allocator>& x, deque<T,Allocator>& y);
}

23.3.3.2 deque constructors, copy, and assignment [deque.cons]

explicit deque(const Allocator& = Allocator());

1

Effects: Constructs an empty deque, using the specified allocator.

2

Complexity: Constant.

explicit deque(size_type n);

3

Effects: Constructs a deque with n value-initialized elements.

4

Requires: T shall be DefaultConstructible.

5

Complexity: Linear in n.

deque(size_type n, const T& value, const Allocator& = Allocator());

6

Effects: Constructs a deque with n copies of value, using the specified allocator.

7

Requires: T shall be CopyInsertable into *this.

8

Complexity: Linear in n.

template <class InputIterator> deque(InputIterator first, InputIterator last, const Allocator& = Allocator());

9

Effects: Constructs a deque equal to the range [first,last), using the specified allocator.

10

Complexity: distance(first, last).

template <class InputIterator> void assign(InputIterator first, InputIterator last);

11

Effects: 

erase(begin(), end());
insert(begin(), first, last);

void assign(size_type n, const T& t);

12

Effects: 

erase(begin(), end());
insert(begin(), n, t);

23.3.3.3 deque capacity [deque.capacity]

void resize(size_type sz);

1

Effects: If sz <= size(), equivalent to erase(begin() + sz, end());. If size() < sz, appends sz - size() value-initialized elements to the sequence.

2

Requires: T shall be DefaultConstructible.

void resize(size_type sz, const T& c);

3

Effects: 

if (sz > size())
  insert(end(), sz-size(), c);
else if (sz < size())
  erase(begin()+sz, end());
else
  ;                 // do nothing
4

Requires: T shall be CopyInsertable into *this.

void shrink_to_fit();

5

Remarks: shrink_to_fit is a non-binding request to reduce memory use. [ Note: The request is non-binding to allow latitude for implementation-specific optimizations.  — end note ]

23.3.3.4 deque modifiers [deque.modifiers]

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);

1

Effects: An insertion in the middle of the deque invalidates all the iterators and references to elements of the deque. An insertion at either end of the deque invalidates all the iterators to the deque, but has no effect on the validity of references to elements of the deque.

2

Remarks: If an exception is thrown other than by the copy constructor, move constructor, assignment operator, or move assignment operator of T there are no effects. If an exception is thrown by the move constructor of a non-CopyInsertable T, the effects are unspecified.

3

Complexity: The complexity is linear in the number of elements inserted plus the lesser of the distances to the beginning and end of the deque. Inserting a single element either at the beginning or end of a deque always takes constant time and causes a single call to a constructor of T.

iterator erase(const_iterator position); iterator erase(const_iterator first, const_iterator last);

4

Effects: An erase operation that erases the last element of a deque invalidates only the past-the-end iterator and all iterators and references to the erased elements. An erase operation that erases the first element of a deque but not the last element invalidates only the erased elements. An erase operation that erases neither the first element nor the last element of a deque invalidates the past-the-end iterator and all iterators and references to all the elements of the deque.

5

Complexity: The number of calls to the destructor is the same as the number of elements erased, but the number of calls to the assignment operator is no more than the lesser of the number of elements before the erased elements and the number of elements after the erased elements.

6

Throws: Nothing unless an exception is thrown by the copy constructor, move constructor, assignment operator, or move assignment operator of T.

23.3.3.5 deque specialized algorithms [deque.special]

template <class T, class Allocator> void swap(deque<T,Allocator>& x, deque<T,Allocator>& y);

1

Effects: 

x.swap(y);

23.3.4 Class template forward_list [forwardlist]

23.3.4.1 Class template forward_list overview [forwardlist.overview]

1

A forward_list is a container that supports forward iterators and allows constant time insert and erase operations anywhere within the sequence, with storage management handled automatically. Fast random access to list elements is not supported. [ Note: It is intended that forward_list have zero space or time overhead relative to a hand-written C-style singly linked list. Features that would conflict with that goal have been omitted. — end note ]

2

A forward_list satisfies all of the requirements of a container (Table [tab:containers.container.requirements]), except that the size() member function is not provided. A forward_list also satisfies all of the requirements for an allocator-aware container (Table [tab:containers.allocatoraware]). In addition, a forward_list provides the assign member functions (Table [tab:containers.sequence.requirements]) and several of the optional container requirements (Table [tab:containers.sequence.optional]). Descriptions are provided here only for operations on forward_list that are not described in that table or for operations where there is additional semantic information.

3

[ Note: Modifying any list requires access to the element preceding the first element of interest, but in a forward_list there is no constant-time way to acess a preceding element. For this reason, ranges that are modified, such as those supplied to erase and splice, must be open at the beginning.  — end note ]

namespace std {
  template <class T, class Allocator = allocator<T> >
  class forward_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;

    // [forwardlist.cons], construct/copy/destroy:
    explicit forward_list(const Allocator& = Allocator());
    explicit forward_list(size_type n);
    forward_list(size_type n, const T& value,
                 const Allocator& = Allocator());
    template <class InputIterator>
      forward_list(InputIterator first, InputIterator last,
                   const Allocator& = Allocator());
    forward_list(const forward_list& x);
    forward_list(forward_list&& x);
    forward_list(const forward_list& x, const Allocator&);
    forward_list(forward_list&& x, const Allocator&);
    forward_list(initializer_list<T>, const Allocator& = Allocator());
    ~forward_list();
    forward_list& operator=(const forward_list& x);
    forward_list& operator=(forward_list&& x);
    forward_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;

    // [forwardlist.iter], iterators:
    iterator before_begin() noexcept;
    const_iterator before_begin() const noexcept;
    iterator begin() noexcept;
    const_iterator begin() const noexcept;
    iterator end() noexcept;
    const_iterator end() const noexcept;

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

    // capacity:
    bool empty() const noexcept;
    size_type max_size() const noexcept;

    // [forwardlist.access], element access:
    reference front();
    const_reference front() const;

    // [forwardlist.modifiers], modifiers:
    template <class... Args> void emplace_front(Args&&... args);
    void push_front(const T& x);
    void push_front(T&& x);
    void pop_front();

    template <class... Args> iterator emplace_after(const_iterator position, Args&&... args);
    iterator insert_after(const_iterator position, const T& x);
    iterator insert_after(const_iterator position, T&& x);

    iterator insert_after(const_iterator position, size_type n, const T& x);
    template <class InputIterator>
      iterator insert_after(const_iterator position, InputIterator first, InputIterator last);
    iterator insert_after(const_iterator position, initializer_list<T> il);

    iterator erase_after(const_iterator position);
    iterator erase_after(const_iterator position, const_iterator last);
    void swap(forward_list&);

    void resize(size_type sz);
    void resize(size_type sz, const value_type& c);
    void clear() noexcept;

    // [forwardlist.ops], forward_list operations:
    void splice_after(const_iterator position, forward_list& x);
    void splice_after(const_iterator position, forward_list&& x);
    void splice_after(const_iterator position, forward_list& x,
                      const_iterator i);
    void splice_after(const_iterator position, forward_list&& x,
                      const_iterator i);
    void splice_after(const_iterator position, forward_list& x,
                      const_iterator first, const_iterator last);
    void splice_after(const_iterator position, forward_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(forward_list& x);
    void merge(forward_list&& x);
    template <class Compare> void merge(forward_list& x, Compare comp);
    template <class Compare> void merge(forward_list&& x, Compare comp);

    void sort();
    template <class Compare> void sort(Compare comp);

    void reverse() noexcept;
  };

  // Comparison operators
  template <class T, class Allocator>
    bool operator==(const forward_list<T,Allocator>& x, const forward_list<T,Allocator>& y);
  template <class T, class Allocator>
    bool operator< (const forward_list<T,Allocator>& x, const forward_list<T,Allocator>& y);
  template <class T, class Allocator>
    bool operator!=(const forward_list<T,Allocator>& x, const forward_list<T,Allocator>& y);
  template <class T, class Allocator>
    bool operator> (const forward_list<T,Allocator>& x, const forward_list<T,Allocator>& y);
  template <class T, class Allocator>
    bool operator>=(const forward_list<T,Allocator>& x, const forward_list<T,Allocator>& y);
  template <class T, class Allocator>
    bool operator<=(const forward_list<T,Allocator>& x, const forward_list<T,Allocator>& y);

  // [forwardlist.spec], specialized algorithms:
  template <class T, class Allocator>
    void swap(forward_list<T,Allocator>& x, forward_list<T,Allocator>& y);
}

23.3.4.2 forward_list constructors, copy, assignment [forwardlist.cons]

explicit forward_list(const Allocator& = Allocator());

1

Effects: Constructs an empty forward_list object using the specified allocator.

2

Complexity: Constant.

explicit forward_list(size_type n);

3

Effects: Constructs a forward_list object with n value-initialized elements.

4

Requires: T shall be DefaultConstructible.

5

Complexity: Linear in n.

forward_list(size_type n, const T& value, const Allocator& = Allocator());

6

Effects: Constructs a forward_list object with n copies of value using the specified allocator.

7

Requires: T shall be CopyInsertable into *this.

8

Complexity: Linear in n.

template <class InputIterator> forward_list(InputIterator first, InputIterator last, const Allocator& = Allocator());

9

Effects: Constructs a forward_list object equal to the range [first,last).

10

Complexity: Linear in distance(first, last).

template <class InputIterator> void assign(InputIterator first, InputIterator last);

11

Effects: clear(); insert_after(before_begin(), first, last);

void assign(size_type n, const T& t);

12

Effects: clear(); insert_after(before_begin(), n, t);

23.3.4.3 forward_list iterators [forwardlist.iter]

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

1

Returns: A non-dereferenceable iterator that, when incremented, is equal to the iterator returned by begin().

2

Effects: cbefore_begin() is equivalent to const_cast<forward_list const&>(*this).before_begin().

3

Remarks: before_begin() == end() shall equal false.

23.3.4.4 forward_list element access [forwardlist.access]

reference front(); const_reference front() const;

1

Returns: *begin()

23.3.4.5 forward_list modifiers [forwardlist.modifiers]

1

None of the overloads of insert_after shall affect the validity of iterators and references, and erase_after shall invalidate only iterators and references to the erased elements. If an exception is thrown during insert_after there shall be no effect. Inserting n elements into a forward_list is linear in n, and the number of calls to the copy or move constructor of T is exactly equal to n. Erasing n elements from a forward_list is linear in n and the number of calls to the destructor of type T is exactly equal to n.

template <class... Args> void emplace_front(Args&&... args);

2

Effects: Inserts an object of type value_type constructed with value_type(std::forward<Args>(args)...) at the beginning of the list.

void push_front(const T& x); void push_front(T&& x);

3

Effects: Inserts a copy of x at the beginning of the list.

void pop_front();

4

Effects: erase_after(before_begin())

iterator insert_after(const_iterator position, const T& x); iterator insert_after(const_iterator position, T&& x);

5

Requires: position is before_begin() or is a dereferenceable iterator in the range [begin(),end()).

6

Effects: Inserts a copy of x after position.

7

Returns: An iterator pointing to the copy of x.

iterator insert_after(const_iterator position, size_type n, const T& x);

8

Requires: position is before_begin() or is a dereferenceable iterator in the range [begin(),end()).

9

Effects: Inserts n copies of x after position.

10

Returns: An iterator pointing to the last inserted copy of x or position if n == 0.

template <class InputIterator> iterator insert_after(const_iterator position, InputIterator first, InputIterator last);

11

Requires: position is before_begin() or is a dereferenceable iterator in the range [begin(),end()). first and last are not iterators in *this.

12

Effects: Inserts copies of elements in [first,last) after position.

13

Returns: An iterator pointing to the last inserted element or position if first == last.

iterator insert_after(const_iterator position, initializer_list<T> il);

14

Effects: insert_after(p, il.begin(), il.end()).

15

Returns: An iterator pointing to the last inserted element or position if i1 is empty.

template <class... Args> iterator emplace_after(const_iterator position, Args&&... args);

16

Requires: position is before_begin() or is a dereferenceable iterator in the range [begin(),end()).

17

Effects: Inserts an object of type value_type constructed with value_type(std::forward<Args>(args)...) after position.

18

Returns: An iterator pointing to the new object.

iterator erase_after(const_iterator position);

19

Requires: The iterator following position is dereferenceable.

20

Effects: Erases the element pointed to by the iterator following position.

21

Returns: An iterator pointing to the element following the one that was erased, or end() if no such element exists.

22

Throws: Nothing.

iterator erase_after(const_iterator position, const_iterator last);

23

Requires: All iterators in the range (position,last) are dereferenceable.

24

Effects: Erases the elements in the range (position,last).

25

Returns: last.

26

Throws: Nothing.

void resize(size_type sz); void resize(size_type sz, const value_type& c);

27

Effects: If sz < distance(begin(), end()), erases the last distance(begin(), end()) - sz elements from the list. Otherwise, inserts sz - distance(begin(), end()) elements at the end of the list. For the first signature the inserted elements are value-initialized, and for the second signature they are copies of c.

28

Requires: T shall be DefaultConstructible for the first form and it shall be CopyInsertable into *this for the second form.

void clear() noexcept;

29

Effects: Erases all elements in the range [begin(),end()).

30

Remarks: Does not invalidate past-the-end iterators.

23.3.4.6 forward_list operations [forwardlist.ops]

void splice_after(const_iterator position, forward_list& x); void splice_after(const_iterator position, forward_list&& x);

1

Requires: position is before_begin() or is a dereferenceable iterator in the range [begin(),end()). &x != this.

2

Effects: Inserts the contents of x after 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.

3

Throws: Nothing.

4

Complexity: Ο(distance(x.begin(), x.end()))

void splice_after(const_iterator position, forward_list& x, const_iterator i); void splice_after(const_iterator position, forward_list&& x, const_iterator i);

5

Requires: position is before_begin() or is a dereferenceable iterator in the range [begin(),end()). The iterator following i is a dereferenceable iterator in x.

6

Effects: Inserts the element following i into *this, following position, and removes it from x. The result is unchanged if position == i or position == ++i. Pointers and references to *i continue to refer to the 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.

7

Throws: Nothing.

8

Complexity: Ο(1)

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

9

Requires: position is before_begin() or is a dereferenceable iterator in the range [begin(),end()). (first,last) is a valid range in x, and all iterators in the range (first,last) are dereferenceable. position is not an iterator in the range (first,last).

10

Effects: Inserts elements in the range (first,last) after position and removes the elements from x. 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.

11

Complexity: Ο(distance(first, last))

void remove(const T& value); template <class Predicate> void remove_if(Predicate pred);

12

Effects: Erases all the elements in the list referred by a list iterator i for which the following conditions hold: *i == value (for remove()), pred(*i) is true (for remove_if()). This operation shall be stable: the relative order of the elements that are not removed is the same as their relative order in the original list. Invalidates only the iterators and references to the erased elements.

13

Throws: Nothing unless an exception is thrown by the equality comparison or the predicate.

14

Complexity: Exactly distance(begin(), end()) applications of the corresponding predicate.

void unique(); template <class BinaryPredicate> void unique(BinaryPredicate pred);

15

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 with no arguments) or pred(*i, *(i - 1)) (for the version with a predicate argument) holds. Invalidates only the iterators and references to the erased elements.

16

Throws: Nothing unless an exception is thrown by the equality comparison or the predicate.

17

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(forward_list& x); void merge(forward_list&& x); template <class Compare> void merge(forward_list& x, Compare comp) template <class Compare> void merge(forward_list&& x, Compare comp)

18

Requires: comp defines a strict weak ordering ([alg.sorting]), and *this and x are both sorted according to this ordering.

19

Effects: Merges x into *this. This operation shall be stable: for equivalent elements in the two lists, the elements from *this shall always precede the elements from x. x is empty after the merge. If an exception is thrown other than by a comparison there are no effects. 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.

20

Complexity: At most distance(begin(), end()) + distance(x.begin(), x.end()) - 1 comparisons.

void sort(); template <class Compare> void sort(Compare comp);

21

Requires: operator< (for the version with no arguments) or comp (for the version with a comparison argument) defines a strict weak ordering ([alg.sorting]).

22

Effects: Sorts the list according to the operator< or the comp function object. This operation shall be stable: the relative order of the equivalent elements is preserved. If an exception is thrown the order of the elements in *this is unspecified. Does not affect the validity of iterators and references.

23

Complexity: Approximately N log N comparisons, where N is distance(begin(), end()).

void reverse() noexcept;

24

Effects: Reverses the order of the elements in the list. Does not affect the validity of iterators and references.

25

Complexity: Linear time.

23.3.4.7 forward_list specialized algorithms [forwardlist.spec]

template <class T, class Allocator> void swap(forward_list<T,Allocator>& x, forward_list<T,Allocator>& y);

1

Effects: x.swap(y)

23.3.5 Class template list [list]

23.3.5.1 Class template list overview [list.overview]

1

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.

2

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);
}
264)

These member functions are only provided by containers whose iterators are random access iterators.

23.3.5.2 list constructors, copy, and assignment [list.cons]

explicit list(const Allocator& = Allocator());

1

Effects: Constructs an empty list, using the specified allocator.

2

Complexity: Constant.

explicit list(size_type n);

3

Effects: Constructs a list with n value-initialized elements.

4

Requires: T shall be DefaultConstructible.

5

Complexity: Linear in n.

list(size_type n, const T& value, const Allocator& = Allocator());

6

Effects: Constructs a list with n copies of value, using the specified allocator.

7

Requires: T shall be CopyInsertable into *this.

8

Complexity: Linear in n.

template <class InputIterator> list(InputIterator first, InputIterator last, const Allocator& = Allocator());

9

Effects: Constructs a list equal to the range [first,last).

10

Complexity: Linear in distance(first, last).

template <class InputIterator> void assign(InputIterator first, InputIterator last);

11

Effects: Replaces the contents of the list with the range [first, last).

void assign(size_type n, const T& t);

12

Effects: Replaces the contents of the list with n copies of t.

23.3.5.3 list capacity [list.capacity]

void resize(size_type sz);

1

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());
2

Requires: T shall be DefaultConstructible.

void resize(size_type sz, const T& c);

3

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
4

Requires: T shall be CopyInsertable into *this.

23.3.5.4 list modifiers [list.modifiers]

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);

1

Remarks: Does not affect the validity of iterators and references. If an exception is thrown there are no effects.

2

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;

3

Effects: Invalidates only the iterators and references to the erased elements.

4

Throws: Nothing.

5

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.

23.3.5.5 list operations [list.ops]

1

Since lists allow fast insertion and erasing from the middle of a list, certain operations are provided specifically for them.266

2

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);

3

Requires: &x != this.

4

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.

5

Throws: Nothing.

6

Complexity: Constant time.

void splice(const_iterator position, list& x, const_iterator i); void splice(const_iterator position, list&& x, const_iterator i);

7

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.

8

Requires: i is a valid dereferenceable iterator of x.

9

Throws: Nothing.

10

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);

11

Effects: Inserts elements in the range [first,last) before position and removes the elements from x.

12

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.

13

Throws: Nothing.

14

Complexity: Constant time if &x == this; otherwise, linear time.

void remove(const T& value); template <class Predicate> void remove_if(Predicate pred);

15

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.

16

Throws: Nothing unless an exception is thrown by *i == value or pred(*i) != false.

17

Remarks: Stable.

18

Complexity: Exactly size() applications of the corresponding predicate.

void unique(); template <class BinaryPredicate> void unique(BinaryPredicate binary_pred);

19

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.

20

Throws: Nothing unless an exception in thrown by *i == *(i-1) or pred(*i, *(i - 1))

21

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);

22

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.

23

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.

24

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().

25

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.

void reverse() noexcept;

26

Effects: Reverses the order of the elements in the list. Does not affect the validity of iterators and references.

27

Complexity: Linear time.

void sort(); template <class Compare> void sort(Compare comp);

28

Requires: operator< (for the first version) or comp (for the second version) shall define a strict weak ordering ([alg.sorting]).

29

Effects: Sorts the list according to the operator< or a Compare function object. Does not affect the validity of iterators and references.

30

Remarks: Stable.

31

Complexity: Approximately N log(N) comparisons, where N == size().

265)

As specified in [allocator.requirements], the requirements in this Clause apply only to lists whose allocators compare equal.

23.3.5.6 list specialized algorithms [list.special]

template <class T, class Allocator> void swap(list<T,Allocator>& x, list<T,Allocator>& y);

1

Effects: 

x.swap(y);

23.3.6 Class template vector [vector]

23.3.6.1 Class template vector overview [vector.overview]

1

A vector is a sequence container that supports random access iterators. In addition, it supports (amortized) constant time insert and erase operations at the end; insert and erase in the middle take linear time. Storage management is handled automatically, though hints can be given to improve efficiency. The elements of a vector are stored contiguously, meaning that if v is a vector<T, Allocator> where T is some type other than bool, then it obeys the identity &v[n] == &v[0] + n for all 0 <= n < v.size().

2

A vector satisfies all of the requirements of a container and 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 push_front, pop_front, and emplace_front member functions, which are not provided. Descriptions are provided here only for operations on vector 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 vector {
  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;

    // [vector.cons], construct/copy/destroy:
    explicit vector(const Allocator& = Allocator());
    explicit vector(size_type n);
    vector(size_type n, const T& value, const Allocator& = Allocator());
    template <class InputIterator>
      vector(InputIterator first, InputIterator last,
             const Allocator& = Allocator());
    vector(const vector& x);
    vector(vector&&);
    vector(const vector&, const Allocator&);
    vector(vector&&, const Allocator&);
    vector(initializer_list<T>, const Allocator& = Allocator());
   ~vector();
    vector& operator=(const vector& x);
    vector& operator=(vector&& x);
    vector& operator=(initializer_list<T>);
    template <class InputIterator>
      void assign(InputIterator first, InputIterator last);
    void assign(size_type n, const T& u);
    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;

    // [vector.capacity], capacity:
    size_type size() const noexcept;
    size_type max_size() const noexcept;
    void      resize(size_type sz);
    void      resize(size_type sz, const T& c);
    size_type capacity() const noexcept;
    bool      empty() const noexcept;
    void      reserve(size_type n);
    void      shrink_to_fit();

    // element access:
    reference       operator[](size_type n);
    const_reference operator[](size_type n) const;
    const_reference at(size_type n) const;
    reference       at(size_type n);
    reference       front();
    const_reference front() const;
    reference       back();
    const_reference back() const;

    // [vector.data], data access
    T*         data() noexcept;
    const T*  data() const noexcept;

    // [vector.modifiers], modifiers:
    template <class... Args> void emplace_back(Args&&... args);
    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 first, const_iterator last);
    void     swap(vector&);
    void     clear() noexcept;
  };

  template <class T, class Allocator>
    bool operator==(const vector<T,Allocator>& x, const vector<T,Allocator>& y);
  template <class T, class Allocator>
    bool operator< (const vector<T,Allocator>& x, const vector<T,Allocator>& y);
  template <class T, class Allocator>
    bool operator!=(const vector<T,Allocator>& x, const vector<T,Allocator>& y);
  template <class T, class Allocator>
    bool operator> (const vector<T,Allocator>& x, const vector<T,Allocator>& y);
  template <class T, class Allocator>
    bool operator>=(const vector<T,Allocator>& x, const vector<T,Allocator>& y);
  template <class T, class Allocator>
    bool operator<=(const vector<T,Allocator>& x, const vector<T,Allocator>& y);

  // [vector.special], specialized algorithms:
  template <class T, class Allocator>
    void swap(vector<T,Allocator>& x, vector<T,Allocator>& y);
}

23.3.6.2 vector constructors, copy, and assignment [vector.cons]

explicit vector(const Allocator& = Allocator());

1

Effects: Constructs an empty vector, using the specified allocator.

2

Complexity: Constant.

explicit vector(size_type n);

3

Effects: Constructs a vector with n value-initialized elements.

4

Requires: T shall be DefaultConstructible.

5

Complexity: Linear in n.

vector(size_type n, const T& value, const Allocator& = Allocator());

6

Effects: Constructs a vector with n copies of value, using the specified allocator.

7

Requires: T shall be CopyInsertable into *this.

8

Complexity: Linear in n.

template <class InputIterator> vector(InputIterator first, InputIterator last, const Allocator& = Allocator());

9

Effects: Constructs a vector equal to the range [first,last), using the specified allocator.

10

Complexity: Makes only N calls to the copy constructor of T (where N is the distance between first and last) and no reallocations if iterators first and last are of forward, bidirectional, or random access categories. It makes order N calls to the copy constructor of T and order log(N) reallocations if they are just input iterators.

template <class InputIterator> void assign(InputIterator first, InputIterator last);

11

Effects: 

erase(begin(), end());
insert(begin(), first, last);

void assign(size_type n, const T& t);

12

Effects: 

erase(begin(), end());
insert(begin(), n, t);

23.3.6.3 vector capacity [vector.capacity]

size_type capacity() const noexcept;

1

Returns: The total number of elements that the vector can hold without requiring reallocation.

void reserve(size_type n);

2

Effects: A directive that informs a vector of a planned change in size, so that it can manage the storage allocation accordingly. After reserve(), capacity() is greater or equal to the argument of reserve if reallocation happens; and equal to the previous value of capacity() otherwise. Reallocation happens at this point if and only if the current capacity is less than the argument of reserve(). If an exception is thrown other than by the move constructor of a non-CopyInsertable type, there are no effects.

3

Complexity: It does not change the size of the sequence and takes at most linear time in the size of the sequence.

4

Throws: length_error if n > max_size().267

5

Remarks: Reallocation invalidates all the references, pointers, and iterators referring to the elements in the sequence. It is guaranteed that no reallocation takes place during insertions that happen after a call to reserve() until the time when an insertion would make the size of the vector greater than the value of capacity().

void shrink_to_fit();

6

Remarks: shrink_to_fit is a non-binding request to reduce capacity() to size(). [ Note: The request is non-binding to allow latitude for implementation-specific optimizations.  — end note ]

void swap(vector& x);

7

Effects: Exchanges the contents and capacity() of *this with that of x.

8

Complexity: Constant time.

void resize(size_type sz);

9

Effects: If sz <= size(), equivalent to erase(begin() + sz, end());. If size() < sz, appends sz - size() value-initialized elements to the sequence.

10

Requires: T shall be CopyInsertable into *this.

void resize(size_type sz, const T& c);

11

Effects: 

if (sz > size())
  insert(end(), sz-size(), c);
else if (sz < size())
  erase(begin()+sz, end());
else
  ;                 // do nothing
12

Requires: If an exception is thrown other than by the move constructor of a non-CopyInsertable T there are no effects.

266)

reserve() uses Allocator::allocate() which may throw an appropriate exception.

23.3.6.4 vector data [vector.data]

T* data() noexcept; const T* data() const noexcept;

1

Returns: A pointer such that [data(),data() + size()) is a valid range. For a non-empty vector, data() == &front().

2

Complexity: Constant time.

23.3.6.5 vector modifiers [vector.modifiers]

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_back(Args&&... args); template <class... Args> iterator emplace(const_iterator position, Args&&... args); void push_back(const T& x); void push_back(T&& x);

1

Remarks: Causes reallocation if the new size is greater than the old capacity. If no reallocation happens, all the iterators and references before the insertion point remain valid. If an exception is thrown other than by the copy constructor, move constructor, assignment operator, or move assignment operator of T or by any InputIterator operation there are no effects. If an exception is thrown by the move constructor of a non-CopyInsertable T, the effects are unspecified.

2

Complexity: The complexity is linear in the number of elements inserted plus the distance to the end of the vector.

iterator erase(const_iterator position); iterator erase(const_iterator first, const_iterator last);

3

Effects: Invalidates iterators and references at or after the point of the erase.

4

Complexity: The destructor of T is called the number of times equal to the number of the elements erased, but the move assignment operator of T is called the number of times equal to the number of elements in the vector after the erased elements.

5

Throws: Nothing unless an exception is thrown by the copy constructor, move constructor, assignment operator, or move assignment operator of T.

23.3.6.6 vector specialized algorithms [vector.special]

template <class T, class Allocator> void swap(vector<T,Allocator>& x, vector<T,Allocator>& y);

1

Effects: 

x.swap(y);

23.3.7 Class vector<bool> [vector.bool]

1

To optimize space allocation, a specialization of vector for bool elements is provided:

namespace std {
  template <class Allocator> class vector<bool, Allocator> {
  public:
    // types:
    typedef bool                                  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 bool                                  value_type;
    typedef Allocator                             allocator_type;
    typedef implementation-defined                pointer;
    typedef implementation-defined                const_pointer;
    typedef std::reverse_iterator<iterator>       reverse_iterator;
    typedef std::reverse_iterator<const_iterator> const_reverse_iterator;

    // bit reference:
    class reference {
      friend class vector;
      reference() noexcept;
    public:
      ~reference();
      operator bool() const noexcept;
      reference& operator=(const bool x) noexcept;
      reference& operator=(const reference& x) noexcept;
      void flip() noexcept;     // flips the bit
    };

    // construct/copy/destroy:
    explicit vector(const Allocator& = Allocator());
    explicit vector(size_type n, const bool& value = bool(),
                    const Allocator& = Allocator());
    template <class InputIterator>
      vector(InputIterator first, InputIterator last,
             const Allocator& = Allocator());
    vector(const vector<bool,Allocator>& x);
    vector(vector<bool,Allocator>&& x);
    vector(const vector&, const Allocator&);
    vector(vector&&, const Allocator&);
    vector(initializer_list<bool>, const Allocator& = Allocator()));
   ~vector();
    vector<bool,Allocator>& operator=(const vector<bool,Allocator>& x);
    vector<bool,Allocator>& operator=(vector<bool,Allocator>&& x);
    vector operator=(initializer_list<bool>);
    template <class InputIterator>
      void assign(InputIterator first, InputIterator last);
    void assign(size_type n, const bool& t);
    void assign(initializer_list<bool>;
    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;

    // capacity:
    size_type size() const noexcept;
    size_type max_size() const noexcept;
    void      resize(size_type sz, bool c = false);
    size_type capacity() const noexcept;
    bool      empty() const noexcept;
    void      reserve(size_type n);
    void      shrink_to_fit();

    // element access:
    reference       operator[](size_type n);
    const_reference operator[](size_type n) const;
    const_reference at(size_type n) const;
    reference       at(size_type n);
    reference       front();
    const_reference front() const;
    reference       back();
    const_reference back() const;

    // modifiers:
    void push_back(const bool& x);
    void pop_back();
    iterator insert(const_iterator position, const bool& x);
    iterator insert (const_iterator position, size_type n, const bool& x);
    template <class InputIterator>
        iterator insert(const_iterator position,
                        InputIterator first, InputIterator last);
    iterator insert(const_iterator position, initializer_list<bool> il);

    iterator erase(const_iterator position);
    iterator erase(const_iterator first, const_iterator last);
    void swap(vector<bool,Allocator>&);
    static void swap(reference x, reference y) noexcept;
    void flip() noexcept;       // flips all bits
    void clear() noexcept;
  };
}
2

Unless described below, all operations have the same requirements and semantics as the primary vector template, except that operations dealing with the bool value type map to bit values in the container storage and allocator_traits::construct ([allocator.traits.members]) is not used to construct these values.

3

There is no requirement that the data be stored as a contiguous allocation of bool values. A space-optimized representation of bits is recommended instead.

4

reference is a class that simulates the behavior of references of a single bit in vector<bool>. The conversion operator returns true when the bit is set, and false otherwise. The assignment operator sets the bit when the argument is (convertible to) true and clears it otherwise. flip reverses the state of the bit.

void flip() noexcept;

5

Effects: Replaces each element in the container with its complement.

static void swap(reference x, reference y) noexcept;

6

Effects: exchanges the contents of x and y as if by

bool b = x;
x = y;
y = b;

template <class Allocator> struct hash<vector<bool, Allocator> >;

7

Requires: the template specialization shall meet the requirements of class template hash ([unord.hash]).

23.4 Associative containers [associative]

23.4.1 In general [associative.general]

1

The header <map> defines the class templates map and multimap; the header <set> defines the class templates set and multiset.

23.4.2 Header <map> synopsis [associative.map.syn]

#include <initializer_list>

namespace std {

  template <class Key, class T, class Compare = less<Key>,
            class Allocator = allocator<pair<const Key, T> > >
    class map;
  template <class Key, class T, class Compare, class Allocator>
    bool operator==(const map<Key,T,Compare,Allocator>& x,
                    const map<Key,T,Compare,Allocator>& y);
  template <class Key, class T, class Compare, class Allocator>
    bool operator< (const map<Key,T,Compare,Allocator>& x,
                    const map<Key,T,Compare,Allocator>& y);
  template <class Key, class T, class Compare, class Allocator>
    bool operator!=(const map<Key,T,Compare,Allocator>& x,
                    const map<Key,T,Compare,Allocator>& y);
  template <class Key, class T, class Compare, class Allocator>
    bool operator> (const map<Key,T,Compare,Allocator>& x,
                    const map<Key,T,Compare,Allocator>& y);
  template <class Key, class T, class Compare, class Allocator>
    bool operator>=(const map<Key,T,Compare,Allocator>& x,
                    const map<Key,T,Compare,Allocator>& y);
  template <class Key, class T, class Compare, class Allocator>
    bool operator<=(const map<Key,T,Compare,Allocator>& x,
                    const map<Key,T,Compare,Allocator>& y);
  template <class Key, class T, class Compare, class Allocator>
    void swap(map<Key,T,Compare,Allocator>& x,
              map<Key,T,Compare,Allocator>& y);

  template <class Key, class T, class Compare = less<Key>,
            class Allocator = allocator<pair<const Key, T> > >
    class multimap;
  template <class Key, class T, class Compare, class Allocator>
    bool operator==(const multimap<Key,T,Compare,Allocator>& x,
                    const multimap<Key,T,Compare,Allocator>& y);
  template <class Key, class T, class Compare, class Allocator>
    bool operator< (const multimap<Key,T,Compare,Allocator>& x,
                    const multimap<Key,T,Compare,Allocator>& y);
  template <class Key, class T, class Compare, class Allocator>
    bool operator!=(const multimap<Key,T,Compare,Allocator>& x,
                    const multimap<Key,T,Compare,Allocator>& y);
  template <class Key, class T, class Compare, class Allocator>
    bool operator> (const multimap<Key,T,Compare,Allocator>& x,
                    const multimap<Key,T,Compare,Allocator>& y);
  template <class Key, class T, class Compare, class Allocator>
    bool operator>=(const multimap<Key,T,Compare,Allocator>& x,
                    const multimap<Key,T,Compare,Allocator>& y);
  template <class Key, class T, class Compare, class Allocator>
    bool operator<=(const multimap<Key,T,Compare,Allocator>& x,
                    const multimap<Key,T,Compare,Allocator>& y);
  template <class Key, class T, class Compare, class Allocator>
    void swap(multimap<Key,T,Compare,Allocator>& x,
              multimap<Key,T,Compare,Allocator>& y);
}

23.4.3 Header <set> synopsis [associative.set.syn]

#include <initializer_list>

namespace std {

  template <class Key, class Compare = less<Key>,
            class Allocator = allocator<Key> >
    class set;
  template <class Key, class Compare, class Allocator>
    bool operator==(const set<Key,Compare,Allocator>& x,
                    const set<Key,Compare,Allocator>& y);
  template <class Key, class Compare, class Allocator>
    bool operator< (const set<Key,Compare,Allocator>& x,
                    const set<Key,Compare,Allocator>& y);
  template <class Key, class Compare, class Allocator>
    bool operator!=(const set<Key,Compare,Allocator>& x,
                    const set<Key,Compare,Allocator>& y);
  template <class Key, class Compare, class Allocator>
    bool operator> (const set<Key,Compare,Allocator>& x,
                    const set<Key,Compare,Allocator>& y);
  template <class Key, class Compare, class Allocator>
    bool operator>=(const set<Key,Compare,Allocator>& x,
                    const set<Key,Compare,Allocator>& y);
  template <class Key, class Compare, class Allocator>
    bool operator<=(const set<Key,Compare,Allocator>& x,
                    const set<Key,Compare,Allocator>& y);
  template <class Key, class Compare, class Allocator>
    void swap(set<Key,Compare,Allocator>& x,
              set<Key,Compare,Allocator>& y);

  template <class Key, class Compare = less<Key>,
            class Allocator = allocator<Key> >
    class multiset;
  template <class Key, class Compare, class Allocator>
    bool operator==(const multiset<Key,Compare,Allocator>& x,
                    const multiset<Key,Compare,Allocator>& y);
  template <class Key, class Compare, class Allocator>
    bool operator< (const multiset<Key,Compare,Allocator>& x,
                    const multiset<Key,Compare,Allocator>& y);
  template <class Key, class Compare, class Allocator>
    bool operator!=(const multiset<Key,Compare,Allocator>& x,
                    const multiset<Key,Compare,Allocator>& y);
  template <class Key, class Compare, class Allocator>
    bool operator> (const multiset<Key,Compare,Allocator>& x,
                    const multiset<Key,Compare,Allocator>& y);
  template <class Key, class Compare, class Allocator>
    bool operator>=(const multiset<Key,Compare,Allocator>& x,
                    const multiset<Key,Compare,Allocator>& y);
  template <class Key, class Compare, class Allocator>
    bool operator<=(const multiset<Key,Compare,Allocator>& x,
                    const multiset<Key,Compare,Allocator>& y);
  template <class Key, class Compare, class Allocator>
    void swap(multiset<Key,Compare,Allocator>& x,
              multiset<Key,Compare,Allocator>& y);
}

23.4.4 Class template map [map]

23.4.4.1 Class template map overview [map.overview]

1

A map is an associative container that supports unique keys (contains at most one of each key value) and provides for fast retrieval of values of another type T based on the keys. The map class supports bidirectional iterators.

2

A map satisfies all of the requirements of a container, of a reversible container ([container.requirements]), of an associative container ([associative.reqmts]), and of an allocator-aware container (Table [tab:containers.allocatoraware]). A map also provides most operations described in ([associative.reqmts]) for unique keys. This means that a map supports the a_uniq operations in ([associative.reqmts]) but not the a_eq operations. For a map<Key,T> the key_type is Key and the value_type is pair<const Key,T>. Descriptions are provided here only for operations on map that are not described in one of those tables or for operations where there is additional semantic information.

namespace std {
  template <class Key, class T, class Compare = less<Key>,
            class Allocator = allocator<pair<const Key, T> > >
  class map {
  public:
    // types:
    typedef Key                                   key_type;
    typedef T                                     mapped_type;
    typedef pair<const Key, T>                    value_type;
    typedef Compare                               key_compare;
    typedef Allocator                             allocator_type;
    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 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;

    class value_compare {
    friend class map;
    protected:
      Compare comp;
      value_compare(Compare c) : comp(c) {}
    public:
      typedef bool result_type;
      typedef value_type first_argument_type;
      typedef value_type second_argument_type;
      bool operator()(const value_type& x, const value_type& y) const {
        return comp(x.first, y.first);
      }
    };

    // [map.cons], construct/copy/destroy:
    explicit map(const Compare& comp = Compare(),
                 const Allocator& = Allocator());
    template <class InputIterator>
      map(InputIterator first, InputIterator last,
          const Compare& comp = Compare(), const Allocator& = Allocator());
    map(const map<Key,T,Compare,Allocator>& x);
    map(map<Key,T,Compare,Allocator>&& x);
    explicit map(const Allocator&);
    map(const map&, const Allocator&);
    map(map&&, const Allocator&);
    map(initializer_list<value_type>,
      const Compare& = Compare(),
      const Allocator& = Allocator());
   ~map();
    map<Key,T,Compare,Allocator>&
      operator=(const map<Key,T,Compare,Allocator>& x);
    map<Key,T,Compare,Allocator>&
      operator=(map<Key,T,Compare,Allocator>&& x);
    map& operator=(initializer_list<value_type>);
    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;

    // capacity:
    bool      empty() const noexcept;
    size_type size() const noexcept;
    size_type max_size() const noexcept;

    // [map.access], element access:
    T& operator[](const key_type& x);
    T& operator[](key_type&& x);
    T&       at(const key_type& x);
    const T& at(const key_type& x) const;

    // [map.modifiers], modifiers:
    template <class... Args> pair<iterator, bool> emplace(Args&&... args);
    template <class... Args> iterator emplace_hint(const_iterator position, Args&&... args);
    pair<iterator, bool> insert(const value_type& x);
    template <class P> pair<iterator, bool> insert(P&& x);
    iterator insert(const_iterator position, const value_type& x);
    template <class P>
      iterator insert(const_iterator position, P&&);
    template <class InputIterator>
      void insert(InputIterator first, InputIterator last);
    void insert(initializer_list<value_type>);

    iterator  erase(const_iterator position);
    size_type erase(const key_type& x);
    iterator  erase(const_iterator first, const_iterator last);
    void swap(map<Key,T,Compare,Allocator>&);
    void clear() noexcept;

    // observers:
    key_compare   key_comp() const;
    value_compare value_comp() const;

    // [map.ops], map operations:
    iterator       find(const key_type& x);
    const_iterator find(const key_type& x) const;
    size_type      count(const key_type& x) const;

    iterator       lower_bound(const key_type& x);
    const_iterator lower_bound(const key_type& x) const;
    iterator       upper_bound(const key_type& x);
    const_iterator upper_bound(const key_type& x) const;

    pair<iterator,iterator>
      equal_range(const key_type& x);
    pair<const_iterator,const_iterator>
      equal_range(const key_type& x) const;
  };

  template <class Key, class T, class Compare, class Allocator>
    bool operator==(const map<Key,T,Compare,Allocator>& x,
                    const map<Key,T,Compare,Allocator>& y);
  template <class Key, class T, class Compare, class Allocator>
    bool operator< (const map<Key,T,Compare,Allocator>& x,
                    const map<Key,T,Compare,Allocator>& y);
  template <class Key, class T, class Compare, class Allocator>
    bool operator!=(const map<Key,T,Compare,Allocator>& x,
                    const map<Key,T,Compare,Allocator>& y);
  template <class Key, class T, class Compare, class Allocator>
    bool operator> (const map<Key,T,Compare,Allocator>& x,
                    const map<Key,T,Compare,Allocator>& y);
  template <class Key, class T, class Compare, class Allocator>
    bool operator>=(const map<Key,T,Compare,Allocator>& x,
                    const map<Key,T,Compare,Allocator>& y);
  template <class Key, class T, class Compare, class Allocator>
    bool operator<=(const map<Key,T,Compare,Allocator>& x,
                    const map<Key,T,Compare,Allocator>& y);

  // specialized algorithms:
  template <class Key, class T, class Compare, class Allocator>
    void swap(map<Key,T,Compare,Allocator>& x,
              map<Key,T,Compare,Allocator>& y);
}

23.4.4.2 map constructors, copy, and assignment [map.cons]

explicit map(const Compare& comp = Compare(), const Allocator& = Allocator());

1

Effects: Constructs an empty map using the specified comparison object and allocator.

2

Complexity: Constant.

template <class InputIterator> map(InputIterator first, InputIterator last, const Compare& comp = Compare(), const Allocator& = Allocator());

3

Requires: If the iterator's dereference operator returns an lvalue or a const rvalue pair<key_type, mapped_type>, then both key_type and mapped_type shall be CopyConstructible.

4

Effects: Constructs an empty map using the specified comparison object and allocator, and inserts elements from the range [first,last).

5

Complexity: Linear in N if the range [first,last) is already sorted using comp and otherwise N logN, where N is last - first.

23.4.4.3 map element access [map.access]

T& operator[](const key_type& x);

1

Effects: If there is no key equivalent to x in the map, inserts value_type(x, T()) into the map.

2

Requires: key_type shall be CopyConstructible and mapped_type shall be DefaultConstructible.

3

Returns: A reference to the mapped_type corresponding to x in *this.

4

Complexity: logarithmic.

T& operator[](key_type&& x);

5

Effects: If there is no key equivalent to x in the map, inserts value_type(std::move(x), T()) into the map.

6

Requires: mapped_type shall be DefaultConstructible.

7

Returns: A reference to the mapped_type corresponding to x in *this.

8

Complexity: logarithmic.

T& at(const key_type& x); const T& at(const key_type& x) const;

9

Returns: A reference to the mapped_type corresponding to x in *this.

10

Throws: An exception object of type out_of_range if no such element is present.

11

Complexity: logarithmic.

23.4.4.4 map modifiers [map.modifiers]

template <class P> pair<iterator, bool> insert(P&& x); template <class P> pair<iterator, bool> insert(const_iterator position, P&& x); template <class InputIterator> void insert(InputIterator first, InputIterator last);

1

Requires: P shall be convertible to value_type.

If P is instantiated as a reference type, then the argument x is copied from. Otherwise x is considered to be an rvalue as it is converted to value_type and inserted into the map. Specifically, in such cases CopyConstructible is not required of key_type or mapped_type unless the conversion from P specifically requires it (e.g., if P is a tuple<const key_type, mapped_type>, then key_type must be CopyConstructible). The signature taking InputIterator parameters does not require CopyConstructible of either key_type or mapped_type if the dereferenced InputIterator returns a non-const rvalue pair<key_type,mapped_type>. Otherwise CopyConstructible is required for both key_type and mapped_type.

23.4.4.5 map operations [map.ops]

iterator find(const key_type& x); const_iterator find(const key_type& x) const; iterator lower_bound(const key_type& x); const_iterator lower_bound(const key_type& x) const; iterator upper_bound(const key_type& x); const_iterator upper_bound(const key_type &x) const; pair<iterator, iterator> equal_range(const key_type &x); pair<const_iterator, const_iterator> equal_range(const key_type& x) const;

1

The find, lower_bound, upper_bound and equal_range member functions each have two versions, one const and the other non-const. In each case the behavior of the two functions is identical except that the const version returns a const_iterator and the non-const version an iterator ([associative.reqmts]).

23.4.4.6 map specialized algorithms [map.special]

template <class Key, class T, class Compare, class Allocator> void swap(map<Key,T,Compare,Allocator>& x, map<Key,T,Compare,Allocator>& y);

1

Effects: 

x.swap(y);

23.4.5 Class template multimap [multimap]

23.4.5.1 Class template multimap overview [multimap.overview]

1

A multimap is an associative container that supports equivalent keys (possibly containing multiple copies of the same key value) and provides for fast retrieval of values of another type T based on the keys. The multimap class supports bidirectional iterators.

2

A multimap satisfies all of the requirements of a container and of a reversible container ([container.requirements]), of an associative container ([associative.reqmts]), and of an allocator-aware container (Table [tab:containers.allocatoraware]). A multimap also provides most operations described in ([associative.reqmts]) for equal keys. This means that a multimap supports the a_eq operations in ([associative.reqmts]) but not the a_uniq operations. For a multimap<Key,T> the key_type is Key and the value_type is pair<const Key,T>. Descriptions are provided here only for operations on multimap that are not described in one of those tables or for operations where there is additional semantic information.

namespace std {
  template <class Key, class T, class Compare = less<Key>,
            class Allocator = allocator<pair<const Key, T> > >
  class multimap {
  public:
    // types:
    typedef Key                                   key_type;
    typedef T                                     mapped_type;
    typedef pair<const Key,T>                     value_type;
    typedef Compare                               key_compare;
    typedef Allocator                             allocator_type;
    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 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;

    class value_compare {
    friend class multimap;
    protected:
      Compare comp;
      value_compare(Compare c) : comp(c) { }
    public:
      typedef bool result_type;
      typedef value_type first_argument_type;
      typedef value_type second_argument_type;
      bool operator()(const value_type& x, const value_type& y) const {
        return comp(x.first, y.first);
      }
    };

    // construct/copy/destroy:
    explicit multimap(const Compare& comp = Compare(),
                      const Allocator& = Allocator());
    template <class InputIterator>
      multimap(InputIterator first, InputIterator last,
               const Compare& comp = Compare(),
               const Allocator& = Allocator());
    multimap(const multimap<Key,T,Compare,Allocator>& x);
    multimap(multimap<Key,T,Compare,Allocator>&& x);
    explicit multimap(const Allocator&);
    multimap(const multimap&, const Allocator&);
    multimap(multimap&&, const Allocator&);
    multimap(initializer_list<value_type>,
      const Compare& = Compare(),
      const Allocator& = Allocator());
   ~multimap();
    multimap<Key,T,Compare,Allocator>&
      operator=(const multimap<Key,T,Compare,Allocator>& x);
    multimap<Key,T,Compare,Allocator>&
      operator=(multimap<Key,T,Compare,Allocator>&& x);
    multimap& operator=(initializer_list<value_type>);
    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;

    // capacity:
    bool           empty() const noexcept;
    size_type      size() const noexcept;
    size_type      max_size() const noexcept;

    // modifiers:
    template <class... Args> iterator emplace(Args&&... args);
    template <class... Args> iterator emplace_hint(const_iterator position, Args&&... args);
    iterator insert(const value_type& x);
    template <class P> iterator insert(P&& x);
    iterator insert(const_iterator position, const value_type& x);
    template <class P> iterator insert(const_iterator position, P&& x);
    template <class InputIterator>
      void insert(InputIterator first, InputIterator last);
    void insert(initializer_list<value_type>);

    iterator  erase(const_iterator position);
    size_type erase(const key_type& x);
    iterator  erase(const_iterator first, const_iterator last);
    void swap(multimap<Key,T,Compare,Allocator>&);
    void clear() noexcept;

    // observers:
    key_compare    key_comp() const;
    value_compare  value_comp() const;

    // map operations:
    iterator       find(const key_type& x);
    const_iterator find(const key_type& x) const;
    size_type      count(const key_type& x) const;

    iterator       lower_bound(const key_type& x);
    const_iterator lower_bound(const key_type& x) const;
    iterator       upper_bound(const key_type& x);
    const_iterator upper_bound(const key_type& x) const;

    pair<iterator,iterator>
      equal_range(const key_type& x);
    pair<const_iterator,const_iterator>
      equal_range(const key_type& x) const;
  };

  template <class Key, class T, class Compare, class Allocator>
    bool operator==(const multimap<Key,T,Compare,Allocator>& x,
                    const multimap<Key,T,Compare,Allocator>& y);
  template <class Key, class T, class Compare, class Allocator>
    bool operator< (const multimap<Key,T,Compare,Allocator>& x,
                    const multimap<Key,T,Compare,Allocator>& y);
  template <class Key, class T, class Compare, class Allocator>
    bool operator!=(const multimap<Key,T,Compare,Allocator>& x,
                    const multimap<Key,T,Compare,Allocator>& y);
  template <class Key, class T, class Compare, class Allocator>
    bool operator> (const multimap<Key,T,Compare,Allocator>& x,
                    const multimap<Key,T,Compare,Allocator>& y);
  template <class Key, class T, class Compare, class Allocator>
    bool operator>=(const multimap<Key,T,Compare,Allocator>& x,
                    const multimap<Key,T,Compare,Allocator>& y);
  template <class Key, class T, class Compare, class Allocator>
    bool operator<=(const multimap<Key,T,Compare,Allocator>& x,
                    const multimap<Key,T,Compare,Allocator>& y);

  // specialized algorithms:
  template <class Key, class T, class Compare, class Allocator>
    void swap(multimap<Key,T,Compare,Allocator>& x,
              multimap<Key,T,Compare,Allocator>& y);
}

23.4.5.2 multimap constructors [multimap.cons]

explicit multimap(const Compare& comp = Compare(), const Allocator& = Allocator());

1

Effects: Constructs an empty multimap using the specified comparison object and allocator.

2

Complexity: Constant.

template <class InputIterator> multimap(InputIterator first, InputIterator last, const Compare& comp = Compare(), const Allocator& = Allocator());

3

Requires: If the iterator's dereference operator returns an lvalue or a const rvalue pair<key_type, mapped_type>, then both key_type and mapped_type shall be CopyConstructible.

4

Effects: Constructs an empty multimap using the specified comparison object and allocator, and inserts elements from the range [first,last).

5

Complexity: Linear in N if the range [first,last) is already sorted using comp and otherwise N logN, where N is last - first.

23.4.5.3 multimap modifiers [multimap.modifiers]

template <class P> iterator insert(P&& x); template <class P> iterator insert(const_iterator position, P&& x);

1

Requires: P shall be convertible to value_type.

If P is instantiated as a reference type, then the argument x is copied from. Otherwise x is considered to be an rvalue as it is converted to value_type and inserted into the map. Specifically, in such cases CopyConstructible is not required of key_type or mapped_type unless the conversion from P specifically requires it (e.g., if P is a tuple<const key_type, mapped_type>, then key_type must be CopyConstructible). The signature taking InputIterator parameters does not require CopyConstructible of either key_type or mapped_type if the dereferenced InputIterator returns a non-const rvalue pair<key_type, mapped_type>. Otherwise CopyConstructible is required for both key_type and mapped_type.

23.4.5.4 multimap operations [multimap.ops]

iterator find(const key_type &x); const_iterator find(const key_type& x) const; iterator lower_bound(const key_type& x); const_iterator lower_bound(const key_type& x) const; pair<iterator, iterator> equal_range(const key_type& x); pair<const_iterator, const_iterator> equal_range(const key_type& x) const;

1

The find, lower_bound, upper_bound, and equal_range member functions each have two versions, one const and one non-const. In each case the behavior of the two versions is identical except that the const version returns a const_iterator and the non-const version an iterator ([associative.reqmts]).

23.4.5.5 multimap specialized algorithms [multimap.special]

template <class Key, class T, class Compare, class Allocator> void swap(multimap<Key,T,Compare,Allocator>& x, multimap<Key,T,Compare,Allocator>& y);

1

Effects: 

x.swap(y);

23.4.6 Class template set [set]

23.4.6.1 Class template set overview [set.overview]

1

A set is an associative container that supports unique keys (contains at most one of each key value) and provides for fast retrieval of the keys themselves. The set class supports bidirectional iterators.

2

A set satisfies all of the requirements of a container, of a reversible container ([container.requirements]), of an associative container ([associative.reqmts]), and of an allocator-aware container (Table [tab:containers.allocatoraware]). A set also provides most operations described in ([associative.reqmts]) for unique keys. This means that a set supports the a_uniq operations in ([associative.reqmts]) but not the a_eq operations. For a set<Key> both the key_type and value_type are Key. Descriptions are provided here only for operations on set that are not described in one of these tables and for operations where there is additional semantic information.

namespace std {
  template <class Key, class Compare = less<Key>,
            class Allocator = allocator<Key> >
  class set {
  public:
    // types:
    typedef Key                                   key_type;
    typedef Key                                   value_type;
    typedef Compare                               key_compare;
    typedef Compare                               value_compare;
    typedef Allocator                             allocator_type;
    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 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;

    // [set.cons], construct/copy/destroy:
    explicit set(const Compare& comp = Compare(),
                 const Allocator& = Allocator());
    template <class InputIterator>
      set(InputIterator first, InputIterator last,
          const Compare& comp = Compare(), const Allocator& = Allocator());
    set(const set<Key,Compare,Allocator>& x);
    set(set<Key,Compare,Allocator>&& x);
    explicit set(const Allocator&);
    set(const set&, const Allocator&);
    set(set&&, const Allocator&);
    set(initializer_list<value_type>,
      const Compare& = Compare(),
      const Allocator& = Allocator());
   ~set();
    set<Key,Compare,Allocator>& operator=
      (const set<Key,Compare,Allocator>& x);
    set<Key,Compare,Allocator>& operator=
      (set<Key,Compare,Allocator>&& x);
    set& operator=(initializer_list<value_type>);
    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;

    // capacity:
    bool          empty() const noexcept;
    size_type     size() const noexcept;
    size_type     max_size() const noexcept;

    // modifiers:
    template <class... Args> pair<iterator, bool> emplace(Args&&... args);
    template <class... Args> iterator emplace_hint(const_iterator position, Args&&... args);
    pair<iterator,bool> insert(const value_type& x);
    pair<iterator,bool> insert(value_type&& x);
    iterator insert(const_iterator position, const value_type& x);
    iterator insert(const_iterator position, value_type&& x);
    template <class InputIterator>
      void insert(InputIterator first, InputIterator last);
    void insert(initializer_list<value_type>);

    iterator  erase(const_iterator position);
    size_type erase(const key_type& x);
    iterator  erase(const_iterator first, const_iterator last);
    void swap(set<Key,Compare,Allocator>&);
    void clear() noexcept;

    // observers:
    key_compare   key_comp() const;
    value_compare value_comp() const;

    // set operations:
    iterator        find(const key_type& x);
    const_iterator  find(const key_type& x) const;

    size_type count(const key_type& x) const;

    iterator        lower_bound(const key_type& x);
    const_iterator  lower_bound(const key_type& x) const;

    iterator        upper_bound(const key_type& x);
    const_iterator  upper_bound(const key_type& x) const;

    pair<iterator,iterator>             equal_range(const key_type& x);
    pair<const_iterator,const_iterator> equal_range(const key_type& x) const;
  };

  template <class Key, class Compare, class Allocator>
    bool operator==(const set<Key,Compare,Allocator>& x,
                    const set<Key,Compare,Allocator>& y);
  template <class Key, class Compare, class Allocator>
    bool operator< (const set<Key,Compare,Allocator>& x,
                    const set<Key,Compare,Allocator>& y);
  template <class Key, class Compare, class Allocator>
    bool operator!=(const set<Key,Compare,Allocator>& x,
                    const set<Key,Compare,Allocator>& y);
  template <class Key, class Compare, class Allocator>
    bool operator> (const set<Key,Compare,Allocator>& x,
                    const set<Key,Compare,Allocator>& y);
  template <class Key, class Compare, class Allocator>
    bool operator>=(const set<Key,Compare,Allocator>& x,
                    const set<Key,Compare,Allocator>& y);
  template <class Key, class Compare, class Allocator>
    bool operator<=(const set<Key,Compare,Allocator>& x,
                    const set<Key,Compare,Allocator>& y);

  // specialized algorithms:
  template <class Key, class Compare, class Allocator>
    void swap(set<Key,Compare,Allocator>& x,
              set<Key,Compare,Allocator>& y);
}

23.4.6.2 set constructors, copy, and assignment [set.cons]

explicit set(const Compare& comp = Compare(), const Allocator& = Allocator());

1

Effects: Constructs an empty set using the specified comparison objects and allocator.

2

Complexity: Constant.

template <class InputIterator> set(InputIterator first, InputIterator last, const Compare& comp = Compare(), const Allocator& = Allocator());

3

Effects: Constructs an empty set using the specified comparison object and allocator, and inserts elements from the range [first,last).

4

Requires: If the iterator's dereference operator returns an lvalue or a non-const rvalue, then Key shall be CopyConstructible.

5

Complexity: Linear in N if the range [first,last) is already sorted using comp and otherwise N logN, where N is last - first.

23.4.6.3 set specialized algorithms [set.special]

template <class Key, class Compare, class Allocator> void swap(set<Key,Compare,Allocator>& x, set<Key,Compare,Allocator>& y);

1

Effects: 

x.swap(y);

23.4.7 Class template multiset [multiset]

23.4.7.1 Class template multiset overview [multiset.overview]

1

A multiset is an associative container that supports equivalent keys (possibly contains multiple copies of the same key value) and provides for fast retrieval of the keys themselves. The multiset class supports bidirectional iterators.

2

A multiset satisfies all of the requirements of a container, of a reversible container ([container.requirements]), of an associative container ([associative.reqmts]), and of an allocator-aware container (Table [tab:containers.allocatoraware]). multiset also provides most operations described in ([associative.reqmts]) for duplicate keys. This means that a multiset supports the a_eq operations in ([associative.reqmts]) but not the a_uniq operations. For a multiset<Key> both the key_type and value_type are Key. Descriptions are provided here only for operations on multiset that are not described in one of these tables and for operations where there is additional semantic information.

namespace std {
  template <class Key, class Compare = less<Key>,
            class Allocator = allocator<Key> >
  class multiset {
  public:
    // types:
    typedef Key                                                     key_type;
    typedef Key                                                     value_type;
    typedef Compare                                                 key_compare;
    typedef Compare                                                 value_compare;
    typedef Allocator                                               allocator_type;
    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 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;

    // construct/copy/destroy:
    explicit multiset(const Compare& comp = Compare(),
                      const Allocator& = Allocator());
    template <class InputIterator>
      multiset(InputIterator first, InputIterator last,
               const Compare& comp = Compare(),
               const Allocator& = Allocator());
    multiset(const multiset<Key,Compare,Allocator>& x);
    multiset(multiset<Key,Compare,Allocator>&& x);
    explicit multiset(const Allocator&);
    multiset(const multiset&, const Allocator&);
    multiset(multiset&&, const Allocator&);
    multiset(initializer_list<value_type>,
      const Compare& = Compare(),
      const Allocator& = Allocator());
   ~multiset();
    multiset<Key,Compare,Allocator>&
        operator=(const multiset<Key,Compare,Allocator>& x);
    multiset<Key,Compare,Allocator>&
        operator=(multiset<Key,Compare,Allocator>&& x);
    multiset& operator=(initializer_list<value_type>);
    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;

    // capacity:
    bool          empty() const noexcept;
    size_type     size() const noexcept;
    size_type     max_size() const noexcept;

    // modifiers:
    template <class... Args> iterator emplace(Args&&... args);
    template <class... Args> iterator emplace_hint(const_iterator position, Args&&... args);
    iterator insert(const value_type& x);
    iterator insert(value_type&& x);
    iterator insert(const_iterator position, const value_type& x);
    iterator insert(const_iterator position, value_type&& x);
    template <class InputIterator>
      void insert(InputIterator first, InputIterator last);
    void insert(initializer_list<value_type>);

    iterator  erase(const_iterator position);
    size_type erase(const key_type& x);
    iterator  erase(const_iterator first, const_iterator last);
    void swap(multiset<Key,Compare,Allocator>&);
    void clear() noexcept;

    // observers:
    key_compare   key_comp() const;
    value_compare value_comp() const;

    // set operations:
    iterator        find(const key_type& x);
    const_iterator  find(const key_type& x) const;

    size_type count(const key_type& x) const;

    iterator        lower_bound(const key_type& x);
    const_iterator  lower_bound(const key_type& x) const;

    iterator        upper_bound(const key_type& x);
    const_iterator  upper_bound(const key_type& x) const;

    pair<iterator,iterator>             equal_range(const key_type& x);
    pair<const_iterator,const_iterator> equal_range(const key_type& x) const;
  };

  template <class Key, class Compare, class Allocator>
    bool operator==(const multiset<Key,Compare,Allocator>& x,
                    const multiset<Key,Compare,Allocator>& y);
  template <class Key, class Compare, class Allocator>
    bool operator< (const multiset<Key,Compare,Allocator>& x,
                    const multiset<Key,Compare,Allocator>& y);
  template <class Key, class Compare, class Allocator>
    bool operator!=(const multiset<Key,Compare,Allocator>& x,
                    const multiset<Key,Compare,Allocator>& y);
  template <class Key, class Compare, class Allocator>
    bool operator> (const multiset<Key,Compare,Allocator>& x,
                    const multiset<Key,Compare,Allocator>& y);
  template <class Key, class Compare, class Allocator>
    bool operator>=(const multiset<Key,Compare,Allocator>& x,
                    const multiset<Key,Compare,Allocator>& y);
  template <class Key, class Compare, class Allocator>
    bool operator<=(const multiset<Key,Compare,Allocator>& x,
                    const multiset<Key,Compare,Allocator>& y);

  // specialized algorithms:
  template <class Key, class Compare, class Allocator>
    void swap(multiset<Key,Compare,Allocator>& x,
              multiset<Key,Compare,Allocator>& y);
}

23.4.7.2 multiset constructors [multiset.cons]

explicit multiset(const Compare& comp = Compare(), const Allocator& = Allocator());

1

Effects: Constructs an empty set using the specified comparison object and allocator.

2

Complexity: Constant.

template <class InputIterator> multiset(InputIterator first, last, const Compare& comp = Compare(), const Allocator& = Allocator());

3

Requires: If the iterator's dereference operator returns an lvalue or a const rvalue, then Key shall be CopyConstructible.

4

Effects: Constructs an empty multiset using the specified comparison object and allocator, and inserts elements from the range [first,last).

5

Complexity: Linear in N if the range [first,last) is already sorted using comp and otherwise N logN, where N is last - first.

23.4.7.3 multiset specialized algorithms [multiset.special]

template <class Key, class Compare, class Allocator> void swap(multiset<Key,Compare,Allocator>& x, multiset<Key,Compare,Allocator>& y);

1

Effects: 

x.swap(y);

23.5 Unordered associative containers [unord]

23.5.1 In general [unord.general]

1

The header <unordered_map> defines the class templates unordered_map and unordered_multimap; the header <unordered_set> defines the class templates unordered_set and unordered_multiset.

23.5.2 Header <unordered_map> synopsis [unord.map.syn]

#include <initializer_list>

namespace std {

  // [unord.map], class template unordered_map:
  template <class Key,
            class T,
            class Hash = hash<Key>,
            class Pred = std::equal_to<Key>,
            class Alloc = std::allocator<std::pair<const Key, T> > >
    class unordered_map;

  // [unord.multimap], class template unordered_multimap:
  template <class Key,
            class T,
            class Hash = hash<Key>,
            class Pred = std::equal_to<Key>,
            class Alloc = std::allocator<std::pair<const Key, T> > >
    class unordered_multimap;

  template <class Key, class T, class Hash, class Pred, class Alloc>
    void swap(unordered_map<Key, T, Hash, Pred, Alloc>& x,
              unordered_map<Key, T, Hash, Pred, Alloc>& y);

  template <class Key, class T, class Hash, class Pred, class Alloc>
    void swap(unordered_multimap<Key, T, Hash, Pred, Alloc>& x,
              unordered_multimap<Key, T, Hash, Pred, Alloc>& y);

  template <class Key, class T, class Hash, class Pred, class Alloc>
    bool operator==(const unordered_map<Key, T, Hash, Pred, Alloc>& a,
                    const unordered_map<Key, T, Hash, Pred, Alloc>& b);
  template <class Key, class T, class Hash, class Pred, class Alloc>
    bool operator!=(const unordered_map<Key, T, Hash, Pred, Alloc>& a,
                    const unordered_map<Key, T, Hash, Pred, Alloc>& b);
  template <class Key, class T, class Hash, class Pred, class Alloc>
    bool operator==(const unordered_multimap<Key, T, Hash, Pred, Alloc>& a,
                    const unordered_multimap<Key, T, Hash, Pred, Alloc>& b);
  template <class Key, class T, class Hash, class Pred, class Alloc>
    bool operator!=(const unordered_multimap<Key, T, Hash, Pred, Alloc>& a,
                    const unordered_multimap<Key, T, Hash, Pred, Alloc>& b);
} // namespace std

23.5.3 Header <unordered_set> synopsis [unord.set.syn]

#include <initializer_list>

namespace std {

  // [unord.set], class template unordered_set:
  template <class Key,
            class Hash = hash<Key>,
            class Pred = std::equal_to<Key>,
            class Alloc = std::allocator<Key> >
    class unordered_set;

  // [unord.multiset], class template unordered_multiset:
  template <class Key,
            class Hash = hash<Key>,
            class Pred = std::equal_to<Key>,
            class Alloc = std::allocator<Key> >
    class unordered_multiset;

  template <class Key, class Hash, class Pred, class Alloc>
    void swap(unordered_set<Key, Hash, Pred, Alloc>& x,
              unordered_set<Key, Hash, Pred, Alloc>& y);

  template <class Key, class Hash, class Pred, class Alloc>
    void swap(unordered_multiset<Key, Hash, Pred, Alloc>& x,
              unordered_multiset<Key, Hash, Pred, Alloc>& y);

  template <class Key, class Hash, class Pred, class Alloc>
    bool operator==(const unordered_set<Key, Hash, Pred, Alloc>& a,
                    const unordered_set<Key, Hash, Pred, Alloc>& b);
  template <class Key, class Hash, class Pred, class Alloc>
    bool operator!=(const unordered_set<Key, Hash, Pred, Alloc>& a,
                    const unordered_set<Key, Hash, Pred, Alloc>& b);
  template <class Key, class Hash, class Pred, class Alloc>
    bool operator==(const unordered_multiset<Key, Hash, Pred, Alloc>& a,
                    const unordered_multiset<Key, Hash, Pred, Alloc>& b);
  template <class Key, class Hash, class Pred, class Alloc>
    bool operator!=(const unordered_multiset<Key, Hash, Pred, Alloc>& a,
                    const unordered_multiset<Key, Hash, Pred, Alloc>& b);
} // namespace std

23.5.4 Class template unordered_map [unord.map]

23.5.4.1 Class template unordered_map overview [unord.map.overview]

1

An unordered_map is an unordered associative container that supports unique keys (an unordered_map contains at most one of each key value) and that associates values of another type mapped_type with the keys. The unordered_map class supports forward iterators.

2

An unordered_map satisfies all of the requirements of a container, of an unordered associative container, and of an allocator-aware container (Table [tab:containers.allocatoraware]). It provides the operations described in the preceding requirements table for unique keys; that is, an unordered_map supports the a_uniq operations in that table, not the a_eq operations. For an unordered_map<Key, T> the key type is Key, the mapped type is T, and the value type is std::pair<const Key, T>.

3

This section only describes operations on unordered_map that are not described in one of the requirement tables, or for which there is additional semantic information.

namespace std {
  template <class Key,
            class T,
            class Hash  = hash<Key>,
            class Pred  = std::equal_to<Key>,
            class Allocator = std::allocator<std::pair<const Key, T> > >
  class unordered_map
  {
  public:
    // types
    typedef Key                                      key_type;
    typedef std::pair<const Key, T>                  value_type;
    typedef T                                        mapped_type;
    typedef Hash                                     hasher;
    typedef Pred                                     key_equal;
    typedef Allocator                                allocator_type;
    typedef typename allocator_type::pointer         pointer;
    typedef typename allocator_type::const_pointer   const_pointer;
    typedef typename allocator_type::reference       reference;
    typedef typename allocator_type::const_reference const_reference;
    typedef implementation-defined                   size_type;
    typedef implementation-defined                   difference_type;

    typedef implementation-defined                    iterator;
    typedef implementation-defined                    const_iterator;
    typedef implementation-defined                    local_iterator;
    typedef implementation-defined                    const_local_iterator;

    // construct/destroy/copy
    explicit unordered_map(size_type n = see below,
                           const hasher& hf = hasher(),
                           const key_equal& eql = key_equal(),
                           const allocator_type& a = allocator_type());
    template <class InputIterator>
      unordered_map(InputIterator f, InputIterator l,
                    size_type n = see below,
                    const hasher& hf = hasher(),
                    const key_equal& eql = key_equal(),
                    const allocator_type& a = allocator_type());
    unordered_map(const unordered_map&);
    unordered_map(unordered_map&&);
    explicit unordered_map(const Allocator&);
    unordered_map(const unordered_map&, const Allocator&);
    unordered_map(unordered_map&&, const Allocator&);
    unordered_map(initializer_list<value_type>,
      size_type = see below,
      const hasher& hf = hasher(),
      const key_equal& eql = key_equal(),
      const allocator_type& a = allocator_type());
    ~unordered_map();
    unordered_map& operator=(const unordered_map&);
    unordered_map& operator=(unordered_map&&);
    unordered_map& operator=(initializer_list<value_type>);
    allocator_type get_allocator() const noexcept;

    // size and capacity
    bool empty() const noexcept;
    size_type size() const noexcept;
    size_type max_size() const noexcept;

    // iterators
    iterator       begin() noexcept;
    const_iterator begin() const noexcept;
    iterator       end() noexcept;
    const_iterator end() const noexcept;
    const_iterator cbegin() const noexcept;
    const_iterator cend() const noexcept;

    // modifiers
    template <class... Args> pair<iterator, bool> emplace(Args&&... args);
    template <class... Args> iterator emplace_hint(const_iterator position, Args&&... args);
    pair<iterator, bool> insert(const value_type& obj);
    template <class P> pair<iterator, bool> insert(P&& obj);
    iterator       insert(const_iterator hint, const value_type& obj);
    template <class P> iterator insert(const_iterator hint, P&& obj);
    template <class InputIterator> void insert(InputIterator first, InputIterator last);
    void insert(initializer_list<value_type>);

    iterator erase(const_iterator position);
    size_type erase(const key_type& k);
    iterator erase(const_iterator first, const_iterator last);
    void clear() noexcept;

    void swap(unordered_map&);

    // observers
    hasher hash_function() const;
    key_equal key_eq() const;

    // lookup
    iterator       find(const key_type& k);
    const_iterator find(const key_type& k) const;
    size_type count(const key_type& k) const;
    std::pair<iterator, iterator>             equal_range(const key_type& k);
    std::pair<const_iterator, const_iterator> equal_range(const key_type& k) const;

    mapped_type& operator[](const key_type& k);
    mapped_type& operator[](key_type&& k);
    mapped_type& at(const key_type& k);
    const mapped_type& at(const key_type& k) const;

    // bucket interface
    size_type bucket_count() const noexcept;
    size_type max_bucket_count() const noexcept;
    size_type bucket_size(size_type n) const;
    size_type bucket(const key_type& k) const;
    local_iterator begin(size_type n);
    const_local_iterator begin(size_type n) const;
    local_iterator end(size_type n);
    const_local_iterator end(size_type n) const;
    const_local_iterator cbegin(size_type n) const;
    const_local_iterator cend(size_type n) const;

    // hash policy
    float load_factor() const noexcept;
    float max_load_factor() const noexcept;
    void max_load_factor(float z);
    void rehash(size_type n);
    void reserve(size_type n);
  };

  template <class Key, class T, class Hash, class Pred, class Alloc>
    void swap(unordered_map<Key, T, Hash, Pred, Alloc>& x,
              unordered_map<Key, T, Hash, Pred, Alloc>& y);

  template <class Key, class T, class Hash, class Pred, class Alloc>
    bool operator==(const unordered_map<Key, T, Hash, Pred, Alloc>& a,
                    const unordered_map<Key, T, Hash, Pred, Alloc>& b);
  template <class Key, class T, class Hash, class Pred, class Alloc>
    bool operator!=(const unordered_map<Key, T, Hash, Pred, Alloc>& a,
                    const unordered_map<Key, T, Hash, Pred, Alloc>& b);
}

23.5.4.2 unordered_map constructors [unord.map.cnstr]

explicit unordered_map(size_type n = see below, const hasher& hf = hasher(), const key_equal& eql = key_equal(), const allocator_type& a = allocator_type());

1

Effects: Constructs an empty unordered_map using the specified hash function, key equality function, and allocator, and using at least n buckets. If n is not provided, the number of buckets is implementation-defined. max_load_factor() returns 1.0.

2

Complexity: Constant.

template <class InputIterator> unordered_map(InputIterator f, InputIterator l, size_type n = see below, const hasher& hf = hasher(), const key_equal& eql = key_equal(), const allocator_type& a = allocator_type());

3

Effects: Constructs an empty unordered_map using the specified hash function, key equality function, and allocator, and using at least n buckets. If n is not provided, the number of buckets is implementation-defined. Then inserts elements from the range [f, l). max_load_factor() returns 1.0.

4

Complexity: Average case linear, worst case quadratic.

23.5.4.3 unordered_map element access [unord.map.elem]

mapped_type& operator[](const key_type& k); mapped_type& operator[](key_type&& k);

1

Requires: mapped_type shall be DefaultConstructible. For the first operator, key_type shall be CopyConstructible. For the second operator, key_type shall be MoveConstructible.

2

Effects: If the unordered_map does not already contain an element whose key is equivalent to k, the first operator inserts the value value_type(k, mapped_type()) and the second operator inserts the value value_type(std::move(k), mapped_type()).

3

Returns: A reference to x.second, where x is the (unique) element whose key is equivalent to k.

4

Complexity: Average case Ο(1), worst case Ο(size()).

mapped_type& at(const key_type& k); const mapped_type& at(const key_type& k) const;

5

Returns: A reference to x.second, where x is the (unique) element whose key is equivalent to k.

6

Throws: An exception object of type out_of_range if no such element is present.

23.5.4.4 unordered_map modifiers [unord.map.modifiers]

template <class P> pair<iterator, bool> insert(P&& obj);

1

Requires: value_type is constructible from std::forward<P>(obj).

2

Effects: Inserts obj converted to value_type if and only if there is no element in the container with key equivalent to the key of value_type(obj).

3

Returns: The bool component of the returned pair object indicates whether the insertion took place and the iterator component points to the element with key equivalent to the key of value_type(obj).

4

Complexity: Average case Ο(1), worst case Ο(size()).

5

Remarks: This signature shall not participate in overload resolution unless P is implicitly convertible to value_type.

template <class P> iterator insert(const_iterator hint, P&& obj);

6

Requires: value_type is constructible from std::forward<P>(obj).

7

Effects: Inserts obj converted to value_type if and only if there is no element in the container with key equivalent to the key of value_type(obj). The iterator hint is a hint pointing to where the search should start.

8

Returns: An iterator that points to the element with key equivalent to the key of value_type(obj).

9

Complexity: Average case Ο(1), worst case Ο(size()).

10

Remarks: This signature shall not participate in overload resolution unless P is implicitly convertible to value_type.

23.5.4.5 unordered_map swap [unord.map.swap]

template <class Key, class T, class Hash, class Pred, class Alloc> void swap(unordered_map<Key, T, Hash, Pred, Alloc>& x, unordered_map<Key, T, Hash, Pred, Alloc>& y);

1

Effects: x.swap(y).

23.5.5 Class template unordered_multimap [unord.multimap]

23.5.5.1 Class template unordered_multimap overview [unord.multimap.overview]

1

An unordered_multimap is an unordered associative container that supports equivalent keys (an instance of unordered_multimap may contain multiple copies of each key value) and that associates values of another type mapped_type with the keys. The unordered_multimap class supports forward iterators.

2

An unordered_multimap satisfies all of the requirements of a container, of an unordered associative container, and of an allocator-aware container (Table [tab:containers.allocatoraware]). It provides the operations described in the preceding requirements table for equivalent keys; that is, an unordered_multimap supports the a_eq operations in that table, not the a_uniq operations. For an unordered_multimap<Key, T> the key type is Key, the mapped type is T, and the value type is std::pair<const Key, T>.

3

This section only describes operations on unordered_multimap that are not described in one of the requirement tables, or for which there is additional semantic information.

namespace std {
  template <class Key,
            class T,
            class Hash  = hash<Key>,
            class Pred  = std::equal_to<Key>,
            class Allocator = std::allocator<std::pair<const Key, T> > >
  class unordered_multimap
  {
  public:
    // types
    typedef Key                                      key_type;
    typedef std::pair<const Key, T>                  value_type;
    typedef T                                        mapped_type;
    typedef Hash                                     hasher;
    typedef Pred                                     key_equal;
    typedef Allocator                                allocator_type;
    typedef typename allocator_type::pointer         pointer;
    typedef typename allocator_type::const_pointer   const_pointer;
    typedef typename allocator_type::reference       reference;
    typedef typename allocator_type::const_reference const_reference;
    typedef implementation-defined                   size_type;
    typedef implementation-defined                   difference_type;

    typedef implementation-defined                   iterator;
    typedef implementation-defined                   const_iterator;
    typedef implementation-defined                   local_iterator;
    typedef implementation-defined                   const_local_iterator;

    // construct/destroy/copy
    explicit unordered_multimap(size_type n = see below,
                                const hasher& hf = hasher(),
                                const key_equal& eql = key_equal(),
                                const allocator_type& a = allocator_type());
    template <class InputIterator>
      unordered_multimap(InputIterator f, InputIterator l,
                         size_type n = see below,
                         const hasher& hf = hasher(),
                         const key_equal& eql = key_equal(),
                         const allocator_type& a = allocator_type());
    unordered_multimap(const unordered_multimap&);
    unordered_multimap(unordered_multimap&&);
    explicit unordered_multimap(const Allocator&);
    unordered_multimap(const unordered_multimap&, const Allocator&);
    unordered_multimap(unordered_multimap&&, const Allocator&);
    unordered_multimap(initializer_list<value_type>,
      size_type = see below,
      const hasher& hf = hasher(),
      const key_equal& eql = key_equal(),
      const allocator_type& a = allocator_type());
    ~unordered_multimap();
    unordered_multimap& operator=(const unordered_multimap&);
    unordered_multimap& operator=(unordered_multimap&&);
    unordered_multimap& operator=(initializer_list<value_type>);
    allocator_type get_allocator() const noexcept;

    // size and capacity
    bool empty() const noexcept;
    size_type size() const noexcept;
    size_type max_size() const noexcept;

    // iterators
    iterator       begin() noexcept;
    const_iterator begin() const noexcept;
    iterator       end() noexcept;
    const_iterator end() const noexcept;
    const_iterator cbegin() const noexcept;
    const_iterator cend() const noexcept;

    // modifiers
    template <class... Args> iterator emplace(Args&&... args);
    template <class... Args> iterator emplace_hint(const_iterator position, Args&&... args);
    iterator insert(const value_type& obj);
    template <class P> iterator insert(P&& obj);
    iterator insert(const_iterator hint, const value_type& obj);
    template <class P> iterator insert(const_iterator hint, P&& obj);
    template <class InputIterator> void insert(InputIterator first, InputIterator last);
    void insert(initializer_list<value_type>);

    iterator erase(const_iterator position);
    size_type erase(const key_type& k);
    iterator erase(const_iterator first, const_iterator last);
    void clear() noexcept;

    void swap(unordered_multimap&);

    // observers
    hasher hash_function() const;
    key_equal key_eq() const;

    // lookup
    iterator       find(const key_type& k);
    const_iterator find(const key_type& k) const;
    size_type count(const key_type& k) const;
    std::pair<iterator, iterator>             equal_range(const key_type& k);
    std::pair<const_iterator, const_iterator> equal_range(const key_type& k) const;

    // bucket interface
    size_type bucket_count() const noexcept;
    size_type max_bucket_count() const noexcept;
    size_type bucket_size(size_type n) const;
    size_type bucket(const key_type& k) const;
    local_iterator begin(size_type n);
    const_local_iterator begin(size_type n) const;
    local_iterator end(size_type n);
    const_local_iterator end(size_type n) const;
    const_local_iterator cbegin(size_type n) const;
    const_local_iterator cend(size_type n) const;

    // hash policy
    float load_factor() const noexcept;
    float max_load_factor() const noexcept;
    void max_load_factor(float z);
    void rehash(size_type n);
    void reserve(size_type n);
  };

  template <class Key, class T, class Hash, class Pred, class Alloc>
    void swap(unordered_multimap<Key, T, Hash, Pred, Alloc>& x,
              unordered_multimap<Key, T, Hash, Pred, Alloc>& y);

  template <class Key, class T, class Hash, class Pred, class Alloc>
    bool operator==(const unordered_multimap<Key, T, Hash, Pred, Alloc>& a,
                    const unordered_multimap<Key, T, Hash, Pred, Alloc>& b);
  template <class Key, class T, class Hash, class Pred, class Alloc>
    bool operator!=(const unordered_multimap<Key, T, Hash, Pred, Alloc>& a,
                    const unordered_multimap<Key, T, Hash, Pred, Alloc>& b);
}

23.5.5.2 unordered_multimap constructors [unord.multimap.cnstr]

explicit unordered_multimap(size_type n = see below, const hasher& hf = hasher(), const key_equal& eql = key_equal(), const allocator_type& a = allocator_type());

1

Effects: Constructs an empty unordered_multimap using the specified hash function, key equality function, and allocator, and using at least n buckets. If n is not provided, the number of buckets is implementation-defined. max_load_factor() returns 1.0.

2

Complexity: Constant.

template <class InputIterator> unordered_multimap(InputIterator f, InputIterator l, size_type n = see below, const hasher& hf = hasher(), const key_equal& eql = key_equal(), const allocator_type& a = allocator_type());

3

Effects: Constructs an empty unordered_multimap using the specified hash function, key equality function, and allocator, and using at least n buckets. If n is not provided, the number of buckets is implementation-defined. Then inserts elements from the range [f, l). max_load_factor() returns 1.0.

4

Complexity: Average case linear, worst case quadratic.

23.5.5.3 unordered_multimap modifiers [unord.multimap.modifiers]

template <class P> iterator insert(P&& obj);

1

Requires: value_type is constructible from std::forward<P>(obj).

2

Effects: Inserts obj converted to value_type.

3

Returns: An iterator that points to the element with key equivalent to the key of value_type(obj).

4

Complexity: Average case Ο(1), worst case Ο(size()).

5

Remarks: This signature shall not participate in overload resolution unless P is implicitly convertible to value_type.

template <class P> iterator insert(const_iterator hint, P&& obj);

6

Requires: value_type is constructible from std::forward<P>(obj).

7

Effects: Inserts obj converted to value_type. The iterator hint is a hint pointing to where the search should start.

8

Returns: An iterator that points to the element with key equivalent to the key of value_type(obj).

9

Complexity: Average case Ο(1), worst case Ο(size()).

10

Remarks: This signature shall not participate in overload resolution unless P is implicitly convertible to value_type.

23.5.5.4 unordered_multimap swap [unord.multimap.swap]

template <class Key, class T, class Hash, class Pred, class Alloc> void swap(unordered_multimap<Key, T, Hash, Pred, Alloc>& x, unordered_multimap<Key, T, Hash, Pred, Alloc>& y);

1

Effects: x.swap(y).

23.5.6 Class template unordered_set [unord.set]

23.5.6.1 Class template unordered_set overview [unord.set.overview]

1

An unordered_set is an unordered associative container that supports unique keys (an unordered_set contains at most one of each key value) and in which the elements' keys are the elements themselves. The unordered_set class supports forward iterators.

2

An unordered_set satisfies all of the requirements of a container, of an unordered associative container, and of an allocator-aware container (Table [tab:containers.allocatoraware]). It provides the operations described in the preceding requirements table for unique keys; that is, an unordered_set supports the a_uniq operations in that table, not the a_eq operations. For an unordered_set<Key> the key type and the value type are both Key. The iterator and const_iterator types are both const iterator types. It is unspecified whether they are the same type.

3

This section only describes operations on unordered_set that are not described in one of the requirement tables, or for which there is additional semantic information.

namespace std {
  template <class Key,
            class Hash  = hash<Key>,
            class Pred  = std::equal_to<Key>,
            class Allocator = std::allocator<Key> >
  class unordered_set
  {
  public:
    // types
    typedef Key                                      key_type;
    typedef Key                                      value_type;
    typedef Hash                                     hasher;
    typedef Pred                                     key_equal;
    typedef Allocator                                allocator_type;
    typedef typename allocator_type::pointer         pointer;
    typedef typename allocator_type::const_pointer   const_pointer;
    typedef typename allocator_type::reference       reference;
    typedef typename allocator_type::const_reference const_reference;
    typedef implementation-defined                   size_type;
    typedef implementation-defined                   difference_type;

    typedef implementation-defined                   iterator;
    typedef implementation-defined                   const_iterator;
    typedef implementation-defined                   local_iterator;
    typedef implementation-defined                   const_local_iterator;

    // construct/destroy/copy
    explicit unordered_set(size_type n = see below,
                           const hasher& hf = hasher(),
                           const key_equal& eql = key_equal(),
                           const allocator_type& a = allocator_type());
    template <class InputIterator>
      unordered_set(InputIterator f, InputIterator l,
                    size_type n = see below,
                    const hasher& hf = hasher(),
                    const key_equal& eql = key_equal(),
                    const allocator_type& a = allocator_type());
    unordered_set(const unordered_set&);
    unordered_set(unordered_set&&);
    explicit unordered_set(const Allocator&);
    unordered_set(const unordered_set&, const Allocator&);
    unordered_set(unordered_set&&, const Allocator&);
    unordered_set(initializer_list<value_type>,
      size_type = see below,
      const hasher& hf = hasher(),
      const key_equal& eql = key_equal(),
      const allocator_type& a = allocator_type());
    ~unordered_set();
    unordered_set& operator=(const unordered_set&);
    unordered_set& operator=(unordered_set&&);
    unordered_set& operator=(initializer_list<value_type>);
    allocator_type get_allocator() const noexcept;

    // size and capacity
    bool empty() const noexcept;
    size_type size() const noexcept;
    size_type max_size() const noexcept;

    // iterators
    iterator       begin() noexcept;
    const_iterator begin() const noexcept;
    iterator       end() noexcept;
    const_iterator end() const noexcept;
    const_iterator cbegin() const noexcept;
    const_iterator cend() const noexcept;

    // modifiers
    template <class... Args> pair<iterator, bool> emplace(Args&&... args);
    template <class... Args> iterator emplace_hint(const_iterator position, Args&&... args);
    pair<iterator, bool> insert(const value_type& obj);
    pair<iterator, bool> insert(value_type&& obj);
    iterator insert(const_iterator hint, const value_type& obj);
    iterator insert(const_iterator hint, value_type&& obj);
    template <class InputIterator> void insert(InputIterator first, InputIterator last);
    void insert(initializer_list<value_type>);

    iterator erase(const_iterator position);
    size_type erase(const key_type& k);
    iterator erase(const_iterator first, const_iterator last);
    void clear() noexcept;

    void swap(unordered_set&);

    // observers
    hasher hash_function() const;
    key_equal key_eq() const;

    // lookup
    iterator       find(const key_type& k);
    const_iterator find(const key_type& k) const;
    size_type count(const key_type& k) const;
    std::pair<iterator, iterator>             equal_range(const key_type& k);
    std::pair<const_iterator, const_iterator> equal_range(const key_type& k) const;

    // bucket interface
    size_type bucket_count() const noexcept;
    size_type max_bucket_count() const noexcept;
    size_type bucket_size(size_type n) const;
    size_type bucket(const key_type& k) const;
    local_iterator begin(size_type n);
    const_local_iterator begin(size_type n) const;
    local_iterator end(size_type n);
    const_local_iterator end(size_type n) const;
    const_local_iterator cbegin(size_type n) const;
    const_local_iterator cend(size_type n) const;

    // hash policy
    float load_factor() const noexcept;
    float max_load_factor() const noexcept;
    void max_load_factor(float z);
    void rehash(size_type n);
    void reserve(size_type n);
  };

  template <class Key, class Hash, class Pred, class Alloc>
    void swap(unordered_set<Key, Hash, Pred, Alloc>& x,
              unordered_set<Key, Hash, Pred, Alloc>& y);

  template <class Key, class T, class Hash, class Pred, class Alloc>
    bool operator==(const unordered_set<Key, T, Hash, Pred, Alloc>& a,
                    const unordered_set<Key, T, Hash, Pred, Alloc>& b);
  template <class Key, class T, class Hash, class Pred, class Alloc>
    bool operator!=(const unordered_set<Key, T, Hash, Pred, Alloc>& a,
                    const unordered_set<Key, T, Hash, Pred, Alloc>& b);
}

23.5.6.2 unordered_set constructors [unord.set.cnstr]

explicit unordered_set(size_type n = see below, const hasher& hf = hasher(), const key_equal& eql = key_equal(), const allocator_type& a = allocator_type());

1

Effects: Constructs an empty unordered_set using the specified hash function, key equality function, and allocator, and using at least n buckets. If n is not provided, the number of buckets is implementation-defined. max_load_factor() returns 1.0.

2

Complexity: Constant.

template <class InputIterator> unordered_set(InputIterator f, InputIterator l, size_type n = see below, const hasher& hf = hasher(), const key_equal& eql = key_equal(), const allocator_type& a = allocator_type());

3

Effects: Constructs an empty unordered_set using the specified hash function, key equality function, and allocator, and using at least n buckets. If n is not provided, the number of buckets is implementation-defined. Then inserts elements from the range [f, l). max_load_factor() returns 1.0.

4

Complexity: Average case linear, worst case quadratic.

23.5.6.3 unordered_set swap [unord.set.swap]

template <class Key, class Hash, class Pred, class Alloc> void swap(unordered_set<Key, Hash, Pred, Alloc>& x, unordered_set<Key, Hash, Pred, Alloc>& y);

1

Effects: x.swap(y).

23.5.7 Class template unordered_multiset [unord.multiset]

23.5.7.1 Class template unordered_multiset overview [unord.multiset.overview]

1

An unordered_multiset is an unordered associative container that supports equivalent keys (an instance of unordered_multiset may contain multiple copies of the same key value) and in which each element's key is the element itself. The unordered_multiset class supports forward iterators.

2

An unordered_multiset satisfies all of the requirements of a container, of an unordered associative container, and of an allocator-aware container (Table [tab:containers.allocatoraware]). It provides the operations described in the preceding requirements table for equivalent keys; that is, an unordered_multiset supports the a_eq operations in that table, not the a_uniq operations. For an unordered_multiset<Key> the key type and the value type are both Key. The iterator and const_iterator types are both const iterator types. It is unspecified whether they are the same type.

3

This section only describes operations on unordered_multiset that are not described in one of the requirement tables, or for which there is additional semantic information.

namespace std {
  template <class Key,
            class Hash  = hash<Key>,
            class Pred  = std::equal_to<Key>,
            class Allocator = std::allocator<Key> >
  class unordered_multiset
  {
  public:
    // types
    typedef Key                                      key_type;
    typedef Key                                      value_type;
    typedef Hash                                     hasher;
    typedef Pred                                     key_equal;
    typedef Allocator                                allocator_type;
    typedef typename allocator_type::pointer         pointer;
    typedef typename allocator_type::const_pointer   const_pointer;
    typedef typename allocator_type::reference       reference;
    typedef typename allocator_type::const_reference const_reference;
    typedef implementation-defined                   size_type;
    typedef implementation-defined                   difference_type;

    typedef implementation-defined                   iterator;
    typedef implementation-defined                   const_iterator;
    typedef implementation-defined                   local_iterator;
    typedef implementation-defined                   const_local_iterator;

    // construct/destroy/copy
    explicit unordered_multiset(size_type n = see below,
                                const hasher& hf = hasher(),
                                const key_equal& eql = key_equal(),
                                const allocator_type& a = allocator_type());
    template <class InputIterator>
      unordered_multiset(InputIterator f, InputIterator l,
                         size_type n = see below,
                         const hasher& hf = hasher(),
                         const key_equal& eql = key_equal(),
                         const allocator_type& a = allocator_type());
    unordered_multiset(const unordered_multiset&);
    unordered_multiset(unordered_multiset&&);
    explicit unordered_multiset(const Allocator&);
    unordered_multiset(const unordered_multiset&, const Allocator&);
    unordered_multiset(unordered_multiset&&, const Allocator&);
    unordered_multiset(initializer_list<value_type>,
      size_type = see below,
      const hasher& hf = hasher(),
      const key_equal& eql = key_equal(),
      const allocator_type& a = allocator_type());
    ~unordered_multiset();
    unordered_multiset& operator=(const unordered_multiset&);
    unordered_multiset operator=(unordered_multiset&&);
    unordered_multiset& operator=(initializer_list<value_type>);
    allocator_type get_allocator() const noexcept;

    // size and capacity
    bool empty() const noexcept;
    size_type size() const noexcept;
    size_type max_size() const noexcept;

    // iterators
    iterator       begin() noexcept;
    const_iterator begin() const noexcept;
    iterator       end() noexcept;
    const_iterator end() const noexcept;
    const_iterator cbegin() const noexcept;
    const_iterator cend() const noexcept;

    // modifiers
    template <class... Args> iterator emplace(Args&&... args);
    template <class... Args> iterator emplace_hint(const_iterator position, Args&&... args);
    iterator insert(const value_type& obj);
    iterator insert(value_type&& obj);
    iterator insert(const_iterator hint, const value_type& obj);
    iterator insert(const_iterator hint, value_type&& obj);
    template <class InputIterator> void insert(InputIterator first, InputIterator last);
    void insert(initializer_list<value_type>);

    iterator erase(const_iterator position);
    size_type erase(const key_type& k);
    iterator erase(const_iterator first, const_iterator last);
    void clear() noexcept;

    void swap(unordered_multiset&);

    // observers
    hasher hash_function() const;
    key_equal key_eq() const;

    // lookup
    iterator       find(const key_type& k);
    const_iterator find(const key_type& k) const;
    size_type count(const key_type& k) const;
    std::pair<iterator, iterator>             equal_range(const key_type& k);
    std::pair<const_iterator, const_iterator> equal_range(const key_type& k) const;

    // bucket interface
    size_type bucket_count() const noexcept;
    size_type max_bucket_count() const noexcept;
    size_type bucket_size(size_type n) const;
    size_type bucket(const key_type& k) const;
    local_iterator begin(size_type n);
    const_local_iterator begin(size_type n) const;
    local_iterator end(size_type n);
    const_local_iterator end(size_type n) const;
    const_local_iterator cbegin(size_type n) const;
    const_local_iterator cend(size_type n) const;

    // hash policy
    float load_factor() const noexcept;
    float max_load_factor() const noexcept;
    void max_load_factor(float z);
    void rehash(size_type n);
    void reserve(size_type n);
  };

  template <class Key, class Hash, class Pred, class Alloc>
    void swap(unordered_multiset<Key, Hash, Pred, Alloc>& x,
              unordered_multiset<Key, Hash, Pred, Alloc>& y);
    template <class Key, class T, class Hash, class Pred, class Alloc>
      bool operator==(const unordered_multiset<Key, T, Hash, Pred, Alloc>& a,
                      const unordered_multiset<Key, T, Hash, Pred, Alloc>& b);
    template <class Key, class T, class Hash, class Pred, class Alloc>
      bool operator!=(const unordered_multiset<Key, T, Hash, Pred, Alloc>& a,
                      const unordered_multiset<Key, T, Hash, Pred, Alloc>& b);
}

23.5.7.2 unordered_multiset constructors [unord.multiset.cnstr]

explicit unordered_multiset(size_type n = see below, const hasher& hf = hasher(), const key_equal& eql = key_equal(), const allocator_type& a = allocator_type());

1

Effects: Constructs an empty unordered_multiset using the specified hash function, key equality function, and allocator, and using at least n buckets. If n is not provided, the number of buckets is implementation-defined. max_load_factor() returns 1.0.

2

Complexity: Constant.

template <class InputIterator> unordered_multiset(InputIterator f, InputIterator l, size_type n = see below, const hasher& hf = hasher(), const key_equal& eql = key_equal(), const allocator_type& a = allocator_type());

3

Effects: Constructs an empty unordered_multiset using the specified hash function, key equality function, and allocator, and using at least n buckets. If n is not provided, the number of buckets is implementation-defined. Then inserts elements from the range [f, l). max_load_factor() returns 1.0.

4

Complexity: Average case linear, worst case quadratic.

23.5.7.3 unordered_multiset swap [unord.multiset.swap]

template <class Key, class Hash, class Pred, class Alloc> void swap(unordered_multiset<Key, Hash, Pred, Alloc>& x, unordered_multiset<Key, Hash, Pred, Alloc>& y);

1

Effects: x.swap(y);

23.6 Container adaptors [container.adaptors]

23.6.1 In general [container.adaptors.general]

1

The headers <queue> and <stack> define the container adaptors queue, priority_queue, and stack. These container adaptors meet the requirements for sequence containers.

2

The container adaptors each take a Container template parameter, and each constructor takes a Container reference argument. This container is copied into the Container member of each adaptor. If the container takes an allocator, then a compatible allocator may be passed in to the adaptor's constructor. Otherwise, normal copy or move construction is used for the container argument.

3

For container adaptors, no swap function throws an exception unless that exception is thrown by the swap of the adaptor's Container or Compare object (if any).

23.6.2 Header <queue> synopsis [queue.syn]

#include <initializer_list>

namespace std {

  template <class T, class Container = deque<T> > class queue;
  template <class T, class Container = vector<T>,
    class Compare = less<typename Container::value_type> >
      class priority_queue;

  template <class T, class Container>
    bool operator==(const queue<T, Container>& x,const queue<T, Container>& y);
  template <class T, class Container>
    bool operator< (const queue<T, Container>& x,const queue<T, Container>& y);
  template <class T, class Container>
    bool operator!=(const queue<T, Container>& x,const queue<T, Container>& y);
  template <class T, class Container>
    bool operator> (const queue<T, Container>& x,const queue<T, Container>& y);
  template <class T, class Container>
    bool operator>=(const queue<T, Container>& x,const queue<T, Container>& y);
  template <class T, class Container>
    bool operator<=(const queue<T, Container>& x,const queue<T, Container>& y);

  template <class T, class Container>
    void swap(queue<T, Container>& x, queue<T, Container>& y) noexcept(noexcept(x.swap(y)));
  template <class T, class Container, class Compare>
    void swap(priority_queue<T, Container, Compare>& x,
              priority_queue<T, Container, Compare>& y) noexcept(noexcept(x.swap(y)));
}

23.6.3 Class template queue [queue]

23.6.3.1 queue definition [queue.defn]

1

Any sequence container supporting operations front(), back(), push_back() and pop_front() can be used to instantiate queue. In particular, list ([list]) and deque ([deque]) can be used.

namespace std {
  template <class T, class Container = deque<T> >
  class queue {
  public:
    typedef typename Container::value_type            value_type;
    typedef typename Container::reference             reference;
    typedef typename Container::const_reference       const_reference;
    typedef typename Container::size_type             size_type;
    typedef          Container                        container_type;
  protected:
    Container c;

  public:
    explicit queue(const Container&);
    explicit queue(Container&& = Container());
    template <class Alloc> explicit queue(const Alloc&);
    template <class Alloc> queue(const Container&, const Alloc&);
    template <class Alloc> queue(Container&&, const Alloc&);
    template <class Alloc> queue(const queue&, const Alloc&);
    template <class Alloc> queue(queue&&, const Alloc&);

    bool              empty() const     { return c.empty(); }
    size_type         size()  const     { return c.size(); }
    reference         front()           { return c.front(); }
    const_reference   front() const     { return c.front(); }
    reference         back()            { return c.back(); }
    const_reference   back() const      { return c.back(); }
    void push(const value_type& x)      { c.push_back(x); }
    void push(value_type&& x)           { c.push_back(std::move(x)); }
    template <class... Args> void emplace(Args&&... args)
      { c.emplace_back(std::forward<Args>(args)...); }
    void pop()                          { c.pop_front(); }
    void swap(queue& q) noexcept(noexcept(swap(c, q.c)))
      { using std::swap; swap(c, q.c); }
  };

  template <class T, class Container>
    bool operator==(const queue<T, Container>& x, const queue<T, Container>& y);
  template <class T, class Container>
    bool operator< (const queue<T, Container>& x, const queue<T, Container>& y);
  template <class T, class Container>
    bool operator!=(const queue<T, Container>& x, const queue<T, Container>& y);
  template <class T, class Container>
    bool operator> (const queue<T, Container>& x, const queue<T, Container>& y);
  template <class T, class Container>
    bool operator>=(const queue<T, Container>& x, const queue<T, Container>& y);
  template <class T, class Container>
    bool operator<=(const queue<T, Container>& x, const queue<T, Container>& y);

  template <class T, class Container>
    void swap(queue<T, Container>& x, queue<T, Container>& y) noexcept(noexcept(x.swap(y)));

  template <class T, class Container, class Alloc>
    struct uses_allocator<queue<T, Container>, Alloc>
      : uses_allocator<Container, Alloc>::type { };
}

23.6.3.2 queue constructors [queue.cons]

explicit queue(const Container& cont);

1

Effects: Initializes c with cont.

explicit queue(Container&& cont = Container());

2

Effects: Initializes c with std::move(cont).

23.6.3.3 queue constructors with allocators [queue.cons.alloc]

1

If uses_allocator<container_type, Alloc>::value is false the constructors in this subclause shall not participate in overload resolution.

template <class Alloc> explicit queue(const Alloc& a);

2

Effects: Initializes c with a.

template <class Alloc> queue(const container_type& cont, const Alloc& a);

3

Effects: Initializes c with cont as the first argument and a as the second argument.

template <class Alloc> queue(container_type&& cont, const Alloc& a);

4

Effects: Initializes c with std::move(cont) as the first argument and a as the second argument.

template <class Alloc> queue(const queue& q, const Alloc& a);

5

Effects: Initializes c with q.c as the first argument and a as the second argument.

template <class Alloc> queue(queue&& q, const Alloc& a);

6

Effects: Initializes c with std::move(q.c) as the first argument and a as the second argument.

23.6.3.4 queue operators [queue.ops]

template <class T, class Container> bool operator==(const queue<T, Container>& x, const queue<T, Container>& y);

1

Returns: x.c == y.c.

template <class T, class Container> bool operator!=(const queue<T, Container>& x, const queue<T, Container>& y);

2

Returns: x.c != y.c.

template <class T, class Container> bool operator< (const queue<T, Container>& x, const queue<T, Container>& y);

3

Returns: x.c < y.c.

template <class T, class Container> bool operator<=(const queue<T, Container>& x, const queue<T, Container>& y);

4

Returns: x.c <= y.c.

template <class T, class Container> bool operator> (const queue<T, Container>& x, const queue<T, Container>& y);

5

Returns: x.c > y.c.

template <class T, class Container> bool operator>=(const queue<T, Container>& x, const queue<T, Container>& y);

6

Returns: x.c >= y.c.

23.6.3.5 queue specialized algorithms [queue.special]

template <class T, class Container> void swap(queue<T, Container>& x, queue<T, Container>& y) noexcept(noexcept(x.swap(y)));

1

Effects: x.swap(y).

23.6.4 Class template priority_queue [priority.queue]

1

Any sequence container with random access iterator and supporting operations front(), push_back() and pop_back() can be used to instantiate priority_queue. In particular, vector ([vector]) and deque ([deque]) can be used. Instantiating priority_queue also involves supplying a function or function object for making priority comparisons; the library assumes that the function or function object defines a strict weak ordering ([alg.sorting]).

namespace std {
  template <class T, class Container = vector<T>,
    class Compare = less<typename Container::value_type> >
  class priority_queue {
  public:
    typedef typename Container::value_type            value_type;
    typedef typename Container::reference             reference;
    typedef typename Container::const_reference       const_reference;
    typedef typename Container::size_type             size_type;
    typedef          Container                        container_type;
  protected:
    Container c;
    Compare comp;

  public:
    priority_queue(const Compare& x, const Container&);
    explicit priority_queue(const Compare& x = Compare(), Container&& = Container());
    template <class InputIterator>
      priority_queue(InputIterator first, InputIterator last,
             const Compare& x, const Container&);
    template <class InputIterator>
      priority_queue(InputIterator first, InputIterator last,
             const Compare& x = Compare(), Container&& = Container());
    template <class Alloc> explicit priority_queue(const Alloc&);
    template <class Alloc> priority_queue(const Compare&, const Alloc&);
    template <class Alloc> priority_queue(const Compare&,
      const Container&, const Alloc&);
    template <class Alloc> priority_queue(const Compare&,
      Container&&, const Alloc&);
    template <class Alloc> priority_queue(const priority_queue&, const Alloc&);
    template <class Alloc> priority_queue(priority_queue&&, const Alloc&);

    bool      empty() const       { return c.empty(); }
    size_type size()  const       { return c.size(); }
    const_reference   top() const { return c.front(); }
    void push(const value_type& x);
    void push(value_type&& x);
    template <class... Args> void emplace(Args&&... args);
    void pop();
    void swap(priority_queue& q) noexcept(
        noexcept(swap(c, q.c)) && noexcept(swap(comp, q.comp)))
      { using std::swap; swap(c, q.c); swap(comp, q.comp); }
  };
  // no equality is provided
  template <class T, class Container, class Compare>
    void swap(priority_queue<T, Container, Compare>& x,
              priority_queue<T, Container, Compare>& y) noexcept(noexcept(x.swap(y)));

  template <class T, class Container, class Compare, class Alloc>
    struct uses_allocator<priority_queue<T, Container, Compare>, Alloc>
      : uses_allocator<Container, Alloc>::type { };
}

23.6.4.1 priority_queue constructors [priqueue.cons]

priority_queue(const Compare& x, const Container& y); explicit priority_queue(const Compare& x = Compare(), Container&& y = Container());

1

Requires: x shall define a strict weak ordering ([alg.sorting]).

2

Effects: Initializes comp with x and c with y (copy constructing or move constructing as appropriate); calls make_heap(c.begin(), c.end(), comp).

template <class InputIterator> priority_queue(InputIterator first, InputIterator last, const Compare& x, const Container& y); template <class InputIterator> priority_queue(InputIterator first, InputIterator last, const Compare& x = Compare(), Container&& y = Container());

3

Requires: x shall define a strict weak ordering ([alg.sorting]).

4

Effects: Initializes comp with x and c with y (copy constructing or move constructing as appropriate); calls c.insert(c.end(), first, last); and finally calls make_heap(c.begin(), c.end(), comp).

23.6.4.2 priority_queue constructors with allocators [priqueue.cons.alloc]

1

If uses_allocator<container_type, Alloc>::value is false the constructors in this subclause shall not participate in overload resolution.

template <class Alloc> explicit priority_queue(const Alloc& a);

2

Effects: Initializes c with a and value-initializes comp.

template <class Alloc> priority_queue(const Compare& compare, const Alloc& a);

3

Effects: Initializes c with a and initializes comp with compare.

template <class Alloc> priority_queue(const Compare& compare, const Container& cont, const Alloc& a);

4

Effects: Initializes c with cont as the first argument and a as the second argument, and initializes comp with compare.

template <class Alloc> priority_queue(const Compare& compare, Container&& cont, const Alloc& a);

5

Effects: Initializes c with std::move(cont) as the first argument and a as the second argument, and initializes comp with compare.

template <class Alloc> priority_queue(const priority_queue& q, const Alloc& a);

6

Effects: Initializes c with q.c as the first argument and a as the second argument, and initializes comp with q.comp.

template <class Alloc> priority_queue(priority_queue&& q, const Alloc& a);

7

Effects: Initializes c with std::move(q.c) as the first argument and a as the second argument, and initializes comp with std::move(q.comp).

23.6.4.3 priority_queue members [priqueue.members]

void push(const value_type& x);

1

Effects: 

c.push_back(x);
push_heap(c.begin(), c.end(), comp);

void push(value_type&& x);

2

Effects: 

c.push_back(std::move(x));
push_heap(c.begin(), c.end(), comp);

template <class... Args> void emplace(Args&&... args)

3

Effects: 

c.emplace_back(std::forward<Args>(args)...);
push_heap(c.begin(), c.end(), comp);

void pop();

4

Effects: 

pop_heap(c.begin(), c.end(), comp);
c.pop_back();

23.6.4.4 priority_queue specialized algorithms [priqueue.special]

template <class T, class Container, Compare> void swap(priority_queue<T, Container, Compare>& x, priority_queue<T, Container, Compare>& y) noexcept(noexcept(x.swap(y)));

1

Effects: x.swap(y).

23.6.5 Class template stack [stack]

1

Any sequence container supporting operations back(), push_back() and pop_back() can be used to instantiate stack. In particular, vector ([vector]), list ([list]) and deque ([deque]) can be used.

23.6.5.1 Header <stack> synopsis [stack.syn]

#include <initializer_list>

namespace std {

  template <class T, class Container = deque<T> > class stack;
  template <class T, class Container>
    bool operator==(const stack<T, Container>& x,const stack<T, Container>& y);
  template <class T, class Container>
    bool operator< (const stack<T, Container>& x,const stack<T, Container>& y);
  template <class T, class Container>
    bool operator!=(const stack<T, Container>& x,const stack<T, Container>& y);
  template <class T, class Container>
    bool operator> (const stack<T, Container>& x,const stack<T, Container>& y);
  template <class T, class Container>
    bool operator>=(const stack<T, Container>& x,const stack<T, Container>& y);
  template <class T, class Container>
    bool operator<=(const stack<T, Container>& x,const stack<T, Container>& y);
  template <class T, class Container>
    void swap(stack<T, Container>& x, stack<T, Container>& y) noexcept(noexcept(x.swap(y)));
}

23.6.5.2 stack definition [stack.defn]

namespace std {
  template <class T, class Container = deque<T> >
  class stack {
  public:
    typedef typename Container::value_type            value_type;
    typedef typename Container::reference             reference;
    typedef typename Container::const_reference       const_reference;
    typedef typename Container::size_type             size_type;
    typedef          Container                        container_type;
  protected:
    Container c;

  public:
    explicit stack(const Container&);
    explicit stack(Container&& = Container());
    template <class Alloc> explicit stack(const Alloc&);
    template <class Alloc> stack(const Container&, const Alloc&);
    template <class Alloc> stack(Container&&, const Alloc&);
    template <class Alloc> stack(const stack&, const Alloc&);
    template <class Alloc> stack(stack&&, const Alloc&);

    bool      empty() const             { return c.empty(); }
    size_type size()  const             { return c.size(); }
    reference         top()             { return c.back(); }
    const_reference   top() const       { return c.back(); }
    void push(const value_type& x)      { c.push_back(x); }
    void push(value_type&& x)           { c.push_back(std::move(x)); }
    template <class... Args> void emplace(Args&&... args)
      { c.emplace_back(std::forward<Args>(args)...); }
    void pop()                          { c.pop_back(); }
    void swap(stack& s) noexcept(noexcept(swap(c, s.c)))
      { using std::swap; swap(c, s.c); }
  };

  template <class T, class Container>
    bool operator==(const stack<T, Container>& x, const stack<T, Container>& y);
  template <class T, class Container>
    bool operator< (const stack<T, Container>& x, const stack<T, Container>& y);
  template <class T, class Container>
    bool operator!=(const stack<T, Container>& x, const stack<T, Container>& y);
  template <class T, class Container>
    bool operator> (const stack<T, Container>& x, const stack<T, Container>& y);
  template <class T, class Container>
    bool operator>=(const stack<T, Container>& x, const stack<T, Container>& y);
  template <class T, class Container>
    bool operator<=(const stack<T, Container>& x, const stack<T, Container>& y);
  template <class T, class Allocator>
    void swap(stack<T,Allocator>& x, stack<T,Allocator>& y);

  template <class T, class Container, class Alloc>
    struct uses_allocator<stack<T, Container>, Alloc>
      : uses_allocator<Container, Alloc>::type { };
}

23.6.5.3 stack constructors [stack.cons]

explicit stack(const Container& cont);

1

Effects: Initializes c with cont.

explicit stack(Container&& const = Container());

2

Effects: Initializes c with std::move(cont).

23.6.5.4 stack constructors with allocators [stack.cons.alloc]

1

If uses_allocator<container_type, Alloc>::value is false the constructors in this subclause shall not participate in overload resolution.

template <class Alloc> explicit stack(const Alloc& a);

2

Effects: Initializes c with a.

template <class Alloc> stack(const container_type& cont, const Alloc& a);

3

Effects: Initializes c with cont as the first argument and a as the second argument.

template <class Alloc> stack(container_type&& cont, const Alloc& a);

4

Effects: Initializes c with std::move(cont) as the first argument and a as the second argument.

template <class Alloc> stack(const stack& s, const Alloc& a);

5

Effects: Initializes c with s.c as the first argument and a as the second argument.

template <class Alloc> stack(stack&& s, const Alloc& a);

6

Effects: Initializes c with std::move(s.c) as the first argument and a as the second argument.

23.6.5.5 stack operators [stack.ops]

template <class T, class Container> bool operator==(const stack<T, Container>& x, const stack<T, Container>& y);

1

Returns: x.c == y.c.

template <class T, class Container> bool operator!=(const stack<T, Container>& x, const stack<T, Container>& y);

2

Returns: x.c != y.c.

template <class T, class Container> bool operator< (const stack<T, Container>& x, const stack<T, Container>& y);

3

Returns: x.c < y.c.

template <class T, class Container> bool operator<=(const stack<T, Container>& x, const stack<T, Container>& y);

4

Returns: x.c <= y.c.

template <class T, class Container> bool operator> (const stack<T, Container>& x, const stack<T, Container>& y);

5

Returns: x.c > y.c.

template <class T, class Container> bool operator>=(const stack<T, Container>& x, const stack<T, Container>& y);

6

Returns: x.c >= y.c.

23.6.5.6 stack specialized algorithms [stack.special]

template <class T, class Container> void swap(stack<T, Container>& x, stack<T, Container>& y) noexcept(noexcept(x.swap(y)));

1

Effects: x.swap(y).