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.
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:
map() : map(Compare()) { }
explicit map(const Compare& comp,
const Allocator& = Allocator());
template <class InputIterator>
map(InputIterator first, InputIterator last,
const Compare& comp = Compare(), const Allocator& = Allocator());
map(const map& x);
map(map&& 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());
template <class InputIterator>
map(InputIterator first, InputIterator last, const Allocator& a)
: map(first, last, Compare(), a) { }
map(initializer_list<value_type> il, const Allocator& a)
: map(il, Compare(), a) { }
~map();
map& operator=(const map& x);
map& operator=(map&& 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&);
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;
template <class K> iterator find(const K& x);
template <class K> const_iterator find(const K& x) const;
size_type count(const key_type& x) const;
template <class K> size_type count(const K& x) const;
iterator lower_bound(const key_type& x);
const_iterator lower_bound(const key_type& x) const;
template <class K> iterator lower_bound(const K& x);
template <class K> const_iterator lower_bound(const K& x) const;
iterator upper_bound(const key_type& x);
const_iterator upper_bound(const key_type& x) const;
template <class K> iterator upper_bound(const K& x);
template <class K> const_iterator upper_bound(const K& 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 K>
pair<iterator, iterator> equal_range(const K& x);
template <class K>
pair<const_iterator, const_iterator> equal_range(const K& 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);
}