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## Class template map

boost::container::map

## Synopsis

    // In header: <boost/container/map.hpp>

    template<typename Key, typename T,
             typename Pred = std::less< std::pair< const Key, T> >,
             typename A = std::allocator<T> >
    class map {
    public:
      // types
      typedef tree_t::key_type                   key_type;
      typedef tree_t::value_type                 value_type;
      typedef tree_t::pointer                    pointer;
      typedef tree_t::const_pointer              const_pointer;
      typedef tree_t::reference                  reference;
      typedef tree_t::const_reference            const_reference;
      typedef T                                  mapped_type;
      typedef Pred                               key_compare;
      typedef tree_t::iterator                   iterator;
      typedef tree_t::const_iterator             const_iterator;
      typedef tree_t::reverse_iterator           reverse_iterator;
      typedef tree_t::const_reverse_iterator     const_reverse_iterator;
      typedef tree_t::size_type                  size_type;
      typedef tree_t::difference_type            difference_type;
      typedef tree_t::allocator_type             allocator_type;
      typedef tree_t::stored_allocator_type      stored_allocator_type;
      typedef std::pair< key_type, mapped_type > nonconst_value_type;
      typedef unspecified                        nonconst_impl_value_type;
      typedef value_compare_impl                 value_compare;

      // construct/copy/destruct
      map();
      explicit map(const Pred &, const allocator_type & = allocator_type());
      template<typename InputIterator>
        map(InputIterator, InputIterator, const Pred & = Pred(),
            const allocator_type & = allocator_type());
      template<typename InputIterator>
        map(ordered_unique_range_t, InputIterator, InputIterator,
            const Pred & = Pred(), const allocator_type & = allocator_type());
      map(const map< Key, T, Pred, A > &);
      map(BOOST_RV_REF(map));
      map& operator=(BOOST_COPY_ASSIGN_REF(map));
      map& operator=(BOOST_RV_REF(map));

      // public member functions
      key_compare key_comp() const;
      value_compare value_comp() const;
      allocator_type get_allocator() const;
      const stored_allocator_type & get_stored_allocator() const;
      stored_allocator_type & get_stored_allocator();
      iterator begin();
      const_iterator begin() const;
      iterator end();
      const_iterator end() const;
      reverse_iterator rbegin();
      const_reverse_iterator rbegin() const;
      reverse_iterator rend();
      const_reverse_iterator rend() const;
      bool empty() const;
      size_type size() const;
      size_type max_size() const;
      mapped_type & operator[](const key_type &);
      mapped_type & operator[](key_type &&);
       BOOST_MOVE_CONVERSION_AWARE_CATCH(operator, key_type, mapped_type &,
                                         priv_subscript) const;
      const T & at(const key_type &) const;
      void swap(map &);
      std::pair< iterator, bool > insert(const value_type &);
      std::pair< iterator, bool > insert(const nonconst_value_type &);
      std::pair< iterator, bool > insert(BOOST_RV_REF(nonconst_value_type));
      std::pair< iterator, bool > insert(BOOST_RV_REF(nonconst_impl_value_type));
      std::pair< iterator, bool > insert(BOOST_RV_REF(value_type));
      iterator insert(iterator, const value_type &);
      iterator insert(iterator, BOOST_RV_REF(nonconst_value_type));
      iterator insert(iterator, BOOST_RV_REF(nonconst_impl_value_type));
      iterator insert(iterator, const nonconst_value_type &);
      iterator insert(iterator, BOOST_RV_REF(value_type));
      template<typename InputIterator> void insert(InputIterator, InputIterator);
      template<class... Args> std::pair< iterator, bool > emplace(Args &&...);
      template<class... Args> iterator emplace_hint(const_iterator, Args &&...);
      iterator erase(const_iterator);
      size_type erase(const key_type &);
      iterator erase(const_iterator, const_iterator);
      void clear();
      iterator find(const key_type &);
      const_iterator find(const key_type &) const;
      size_type count(const key_type &) const;
      iterator lower_bound(const key_type &);
      const_iterator lower_bound(const key_type &) const;
      iterator upper_bound(const key_type &);
      const_iterator upper_bound(const key_type &) const;
      std::pair< iterator, iterator > equal_range(const key_type &);
      std::pair< const_iterator, const_iterator >
      equal_range(const key_type &) const;
    };

## Description

A map is a kind of 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 and of a reversible container and of an associative container. For a map<Key,T> the key_type is Key and the value_type is std::pair<const Key,T>.

Pred is the ordering function for Keys (e.g. std::less<Key>).

A is the allocator to allocate the value_types (e.g. allocator< std::pair<const Key, T> > ).

### `map` public construct/copy/destruct

1.     map();

   Effects: Default constructs an empty map.

   Complexity: Constant.

2.     explicit map(const Pred & comp, const allocator_type & a = allocator_type());

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

   Complexity: Constant.

3.     template<typename InputIterator>
         map(InputIterator first, InputIterator last, const Pred & comp = Pred(),
             const allocator_type & a = allocator_type());

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

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

4.     template<typename InputIterator>
         map(ordered_unique_range_t, InputIterator first, InputIterator last,
             const Pred & comp = Pred(),
             const allocator_type & a = allocator_type());

   Effects: Constructs an empty map using the specified comparison object and allocator, and inserts elements from the ordered unique range [first ,last). This function is more efficient than the normal range creation for ordered ranges.

   Requires: [first ,last) must be ordered according to the predicate and must be unique values.

   Complexity: Linear in N.

5.     map(const map< Key, T, Pred, A > & x);

   Effects: Copy constructs a map.

   Complexity: Linear in x.size().

6.     map(BOOST_RV_REF(map) x);

   Effects: Move constructs a map. Constructs *this using x's resources.

   Complexity: Construct.

   Postcondition: x is emptied.

7.     map& operator=(BOOST_COPY_ASSIGN_REF(map) x);

   Effects: Makes *this a copy of x.

   Complexity: Linear in x.size().

8.     map& operator=(BOOST_RV_REF(map) x);

   Effects: this->swap(x.get()).

   Complexity: Constant.

### `map` public member functions

1.     key_compare key_comp() const;

   Effects: Returns the comparison object out of which a was constructed.

   Complexity: Constant.

2.     value_compare value_comp() const;

   Effects: Returns an object of value_compare constructed out of the comparison object.

   Complexity: Constant.

3.     allocator_type get_allocator() const;

   Effects: Returns a copy of the Allocator that was passed to the object's constructor.

   Complexity: Constant.

4.     const stored_allocator_type & get_stored_allocator() const;

5.     stored_allocator_type & get_stored_allocator();

6.     iterator begin();

   Effects: Returns an iterator to the first element contained in the container.

   Throws: Nothing.

   Complexity: Constant.

7.     const_iterator begin() const;

   Effects: Returns a const_iterator to the first element contained in the container.

   Throws: Nothing.

   Complexity: Constant.

8.     iterator end();

   Effects: Returns an iterator to the end of the container.

   Throws: Nothing.

   Complexity: Constant.

9.     const_iterator end() const;

   Effects: Returns a const_iterator to the end of the container.

   Throws: Nothing.

   Complexity: Constant.

10.     reverse_iterator rbegin();

    Effects: Returns a reverse_iterator pointing to the beginning of the reversed container.

    Throws: Nothing.

    Complexity: Constant.

11.     const_reverse_iterator rbegin() const;

    Effects: Returns a const_reverse_iterator pointing to the beginning of the reversed container.

    Throws: Nothing.

    Complexity: Constant.

12.     reverse_iterator rend();

    Effects: Returns a reverse_iterator pointing to the end of the reversed container.

    Throws: Nothing.

    Complexity: Constant.

13.     const_reverse_iterator rend() const;

    Effects: Returns a const_reverse_iterator pointing to the end of the reversed container.

    Throws: Nothing.

    Complexity: Constant.

14.     bool empty() const;

    Effects: Returns true if the container contains no elements.

    Throws: Nothing.

    Complexity: Constant.

15.     size_type size() const;

    Effects: Returns the number of the elements contained in the container.

    Throws: Nothing.

    Complexity: Constant.

16.     size_type max_size() const;

    Effects: Returns the largest possible size of the container.

    Throws: Nothing.

    Complexity: Constant.

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

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

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

    Complexity: Logarithmic.

18.     mapped_type & operator[](key_type && k);

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

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

    Complexity: Logarithmic.

19.      BOOST_MOVE_CONVERSION_AWARE_CATCH(operator, key_type, mapped_type &,
                                           priv_subscript) const;

    Returns: A reference to the element whose key is equivalent to x. Throws: An exception object of type out_of_range if no such element is present. Complexity: logarithmic.

20.     const T & at(const key_type & k) const;

    Returns: A reference to the element whose key is equivalent to x. Throws: An exception object of type out_of_range if no such element is present. Complexity: logarithmic.

21.     void swap(map & x);

    Effects: Swaps the contents of *this and x.

    Throws: Nothing.

    Complexity: Constant.

22.     std::pair< iterator, bool > insert(const value_type & x);

    Effects: Inserts x if and only if there is no element in the container with key equivalent to the key of x.

    Returns: 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 x.

    Complexity: Logarithmic.

23.     std::pair< iterator, bool > insert(const nonconst_value_type & x);

    Effects: Inserts a new value_type created from the pair if and only if there is no element in the container with key equivalent to the key of x.

    Returns: 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 x.

    Complexity: Logarithmic.

24.     std::pair< iterator, bool > insert(BOOST_RV_REF(nonconst_value_type) x);

    Effects: Inserts a new value_type move constructed from the pair if and only if there is no element in the container with key equivalent to the key of x.

    Returns: 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 x.

    Complexity: Logarithmic.

25.     std::pair< iterator, bool > insert(BOOST_RV_REF(nonconst_impl_value_type) x);

    Effects: Inserts a new value_type move constructed from the pair if and only if there is no element in the container with key equivalent to the key of x.

    Returns: 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 x.

    Complexity: Logarithmic.

26.     std::pair< iterator, bool > insert(BOOST_RV_REF(value_type) x);

    Effects: Move constructs a new value from x if and only if there is no element in the container with key equivalent to the key of x.

    Returns: 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 x.

    Complexity: Logarithmic.

27.     iterator insert(iterator position, const value_type & x);

    Effects: Inserts a copy of x in the container if and only if there is no element in the container with key equivalent to the key of x. p is a hint pointing to where the insert should start to search.

    Returns: An iterator pointing to the element with key equivalent to the key of x.

    Complexity: Logarithmic in general, but amortized constant if t is inserted right before p.

28.     iterator insert(iterator position, BOOST_RV_REF(nonconst_value_type) x);

    Effects: Move constructs a new value from x if and only if there is no element in the container with key equivalent to the key of x. p is a hint pointing to where the insert should start to search.

    Returns: An iterator pointing to the element with key equivalent to the key of x.

    Complexity: Logarithmic in general, but amortized constant if t is inserted right before p.

29.     iterator insert(iterator position, BOOST_RV_REF(nonconst_impl_value_type) x);

    Effects: Move constructs a new value from x if and only if there is no element in the container with key equivalent to the key of x. p is a hint pointing to where the insert should start to search.

    Returns: An iterator pointing to the element with key equivalent to the key of x.

    Complexity: Logarithmic in general, but amortized constant if t is inserted right before p.

30.     iterator insert(iterator position, const nonconst_value_type & x);

    Effects: Inserts a copy of x in the container. p is a hint pointing to where the insert should start to search.

    Returns: An iterator pointing to the element with key equivalent to the key of x.

    Complexity: Logarithmic.

31.     iterator insert(iterator position, BOOST_RV_REF(value_type) x);

    Effects: Inserts an element move constructed from x in the container. p is a hint pointing to where the insert should start to search.

    Returns: An iterator pointing to the element with key equivalent to the key of x.

    Complexity: Logarithmic.

32.     template<typename InputIterator>
          void insert(InputIterator first, InputIterator last);

    Requires: first, last are not iterators into *this.

    Effects: inserts each element from the range [first,last) if and only if there is no element with key equivalent to the key of that element.

    Complexity: At most N log(size()+N) (N is the distance from first to last)

33.     template<class... Args> std::pair< iterator, bool > emplace(Args &&... args);

    Effects: Inserts an object x of type T constructed with std::forward<Args>(args)... in the container if and only if there is no element in the container with an equivalent key. p is a hint pointing to where the insert should start to search.

    Returns: 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 x.

    Complexity: Logarithmic in general, but amortized constant if t is inserted right before p.

34.     template<class... Args>
          iterator emplace_hint(const_iterator hint, Args &&... args);

    Effects: Inserts an object of type T constructed with std::forward<Args>(args)... in the container if and only if there is no element in the container with an equivalent key. p is a hint pointing to where the insert should start to search.

    Returns: An iterator pointing to the element with key equivalent to the key of x.

    Complexity: Logarithmic in general, but amortized constant if t is inserted right before p.

35.     iterator erase(const_iterator position);

    Effects: Erases the element pointed to by position.

    Returns: Returns an iterator pointing to the element immediately following q prior to the element being erased. If no such element exists, returns end().

    Complexity: Amortized constant time

36.     size_type erase(const key_type & x);

    Effects: Erases all elements in the container with key equivalent to x.

    Returns: Returns the number of erased elements.

    Complexity: log(size()) + count(k)

37.     iterator erase(const_iterator first, const_iterator last);

    Effects: Erases all the elements in the range [first, last).

    Returns: Returns last.

    Complexity: log(size())+N where N is the distance from first to last.

38.     void clear();

    Effects: erase(a.begin(),a.end()).

    Postcondition: size() == 0.

    Complexity: linear in size().

39.     iterator find(const key_type & x);

    Returns: An iterator pointing to an element with the key equivalent to x, or end() if such an element is not found.

    Complexity: Logarithmic.

40.     const_iterator find(const key_type & x) const;

    Returns: A const_iterator pointing to an element with the key equivalent to x, or end() if such an element is not found.

    Complexity: Logarithmic.

41.     size_type count(const key_type & x) const;

    Returns: The number of elements with key equivalent to x.

    Complexity: log(size())+count(k)

42.     iterator lower_bound(const key_type & x);

    Returns: An iterator pointing to the first element with key not less than k, or a.end() if such an element is not found.

    Complexity: Logarithmic

43.     const_iterator lower_bound(const key_type & x) const;

    Returns: A const iterator pointing to the first element with key not less than k, or a.end() if such an element is not found.

    Complexity: Logarithmic

44.     iterator upper_bound(const key_type & x);

    Returns: An iterator pointing to the first element with key not less than x, or end() if such an element is not found.

    Complexity: Logarithmic

45.     const_iterator upper_bound(const key_type & x) const;

    Returns: A const iterator pointing to the first element with key not less than x, or end() if such an element is not found.

    Complexity: Logarithmic

46.     std::pair< iterator, iterator > equal_range(const key_type & x);

    Effects: Equivalent to std::make_pair(this->lower_bound(k), this->upper_bound(k)).

    Complexity: Logarithmic

47.     std::pair< const_iterator, const_iterator >
        equal_range(const key_type & x) const;

    Effects: Equivalent to std::make_pair(this->lower_bound(k), this->upper_bound(k)).

    Complexity: Logarithmic