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multimap(3C++)			       -			multimap(3C++)

Standard C++ Library Copyright 1998, Rogue Wave Software, Inc.

NAME
       multimap

	-  An  associative container that gives access to non-key values using
       keys. multimap keys are not required to be unique. A multimap  supports
       bidirectional iterators.

SYNOPSIS
       #include <map>
       template <class Key, class T, class Compare = less<Key>,
	 class Allocator = allocator<pair<const Key, T>> >
class multimap;

DESCRIPTION
       multimap_<Key_,T,_Compare,_Allocator>  gives fast access to stored val‐
       ues of type T that are indexed by keys of type Key. The default	opera‐
       tion  for key comparison is the < operator. Unlike map, multimap allows
       insertion of duplicate keys.

       multimap uses bidirectional iterators that  point  to  an  instance  of
       pair<const  Key	x,  T  y> where x is the key and y is the stored value
       associated with that key.   The definition of multimap includes a type‐
       def to this pair called value_type.

       The  types used for both the template parameters Key and T must include
       the following (where T is the type, t is a value of T and u is a	 const
       value of T):

       Copy constructors   T(t) and T(u)

       Destructor   t.~T()

       Address of   &t and &u yielding T* and const T* respectively

       Assignment   t = a where a is a (possibly const) value of T

       The  type  used	for  the  Compare  template parameter must satisfy the
       requirements for binary functions.

INTERFACE
       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 typename
	  Allocator::reference	      reference;
  typedef typename
	  Allocator::const_reference  const_reference;

  class iterator;
  class const_iterator;

  typedef typename
	  Allocator::size_type	      size_type;
  typedef typename
	  Allocator::difference_type  difference_type;

  typedef typename std::reverse_iterator<iterator>
			reverse_iterator;
  typedef typename std::reverse_iterator<const_iterator>
			const_reverse_iterator;

class value_compare
    : public binary_function<value_type, value_type, bool>

    {
    friend class multimap<Key, T, Compare, Allocator>;

    protected :
      Compare comp;
      value_compare (Compare C) : comp(c) {}
    public :
      bool operator() (const value_type&,
		       const value_type&) const;
    };

// Construct/Copy/Destroy

  explicit multimap (const Compare& = Compare(),
		     const Allocator& =
		     Allocator());
  template <class InputIterator>
   multimap (InputIterator, InputIterator,
	     const Compare& = Compare(),
	     const Allocator& = Allocator());
  multimap (const multimap<Key, T, Compare, Allocator>&);
   ~multimap ();
  multimap<Key, T, Compare, Allocator>& operator=
       (const multimap<Key, T, Compare, Allocator>&);
  allocator_type get_allocator () const;

// Iterators

  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;

// Capacity

  bool empty () const;
  size_type size () const;
  size_type max_size () const;

// Modifiers

  iterator insert (const value_type&);
  iterator insert (iterator, const value_type&);
  template <class InputIterator>
   void insert (InputIterator, InputIterator);

  void erase (iterator);
  size_type erase (const key_type&);
  void erase (iterator, iterator);
  void swap (multimap<Key, T, Compare, Allocator>&);
  void clear ();

// Observers

  key_compare key_comp () const;
  value_compare value_comp () const;

// Multimap operations

  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;
  pair<iterator, iterator> equal_range (const key_type&);
  pair<const_iterator, const_iterator>
    equal_range (const key_type&) const;
};
// Non-member Operators

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

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

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

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

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

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

// Specialized Algorithms

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

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

   Constructs an empty multimap that uses the optional relation comp to	 order
   keys and the allocator alloc for all storage management.

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

   Constructs  a multimap containing values in the range [first, last).	  Cre‐
   ation of the new multimap is only guaranteed to succeed  if	the  iterators
   first and last return values of type pair<class Key, class T>.

multimap(const multimap<;Key, T, Compare, Allocator>& x);

   Creates a new multimap by copying all pairs of key and value from x.

DESTRUCTORS
       ~multimap();

   Releases any allocated memory for this multimap.

ASSIGNMENT OPERATORS
       multimap<Key, T, Compare, Allocator>&
       operator=(const multimap<Key, T, Compare, Allocator>& x);

   Replaces the contents of *this with a copy of the multimap x.

ALLOCATORS
       allocator_type
       get_allocator() const;

   Returns a copy of the allocator used by self for storage management.

ITERATORS
       iterator
       begin();

   Returns  a  bidirectional  iterator pointing to the first element stored in
   the multimap. "First" is defined by	the  multimap's	 comparison  operator,
   Compare.

const_iterator
begin() const;

   Returns  a  const_iterator pointing to the first element stored in the mul‐
   timap. "First" is defined by the multimap's comparison operator, Compare.

iterator
end();

   Returns a bidirectional iterator pointing to the last element stored in the
   multimap (in other words, the off-the-end value).

const_iterator
end() const;

   Returns  a  const_iterator  pointing to the last element stored in the mul‐
   timap.

reverse_iterator
rbegin();

   Returns a reverse_iterator pointing to the first element stored in the mul‐
   timap. "First" is defined by the multimap's comparison operator, Compare.

const_reverse_iterator
rbegin() const;

   Returns  a  const_reverse_iterator  pointing to the first element stored in
   the multimap.

reverse_iterator
rend();

   Returns a reverse_iterator pointing to the last element stored in the  mul‐
   timap (in other words, the off-the-end value).

const_reverse_iterator
rend() const;

   Returns a const_reverse_iterator pointing to the last element stored in the
   multimap.

MEMBER FUNCTIONS
       void
       clear();

   Erases all elements from the self.

size_type
count(const key_type& x) const;

   Returns the number of elements in the multimap with the key value x.

bool
empty() const;

   Returns true if the multimap is empty, false otherwise.

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

   Returns the pair (lower_bound(x), upper_bound(x)).

void
erase(iterator first, iterator last);

   If the iterators first and last point to the	 same  multimap	 and  last  is
   reachable  from  first, all elements in the range (first, last) are deleted
   from the multimap. Returns an iterator pointing to  the  element  following
   the	last  deleted  element	or  end(), if there were no elements after the
   deleted range.

void
erase(iterator position);

   Deletes the multimap element pointed to by the iterator  position.  Returns
   an  iterator	 pointing  to  the  element  following the deleted element, or
   end(), if the deleted item was the last one in this list.

size_type
erase(const key_type& x);

   Deletes the elements with the key value x  from  the	 map,  if  any	exist.
   Returns the number of deleted elements, or 0 otherwise.

iterator
find(const key_type& x);

   Searches the multimap for a pair with the key value x and returns an itera‐
   tor to that pair if it is found. If such a pair  is	not  found  the	 value
   end() is returned.

const_iterator
find(const key_type& x) const;

   Same as find above but returns a const_iterator.

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

   x  is  inserted  into  the  multimap.  A position may be supplied as a hint
   regarding where to do the insertion. If the insertion is done  right	 after
   position,  then  it takes amortized constant time. Otherwise it takes O(log
   N) time.

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

   Copies of each element in the range [first, last)  are  inserted  into  the
   multimap.  The  iterators  first  and  last	must  return  values  of  type
   pair<T1,T2>. This operation takes approximately O(N*log(size()+N)) time.

key_compare
key_comp() const;

   Returns a function object capable of comparing key values using the compar‐
   ison operation, Compare, of the current multimap.

iterator
lower_bound(const key_type& x);

   Returns an iterator to the first multimap element whose key is greater than
   or equal to x. If no such element exists, then end() is returned.

const_iterator
lower_bound(const key_type& x) const;

   Same as lower_bound above but returns a const_iterator.

size_type
max_size() const;

   Returns the maximum possible size of the multimap.

size_type
size() const;

   Returns the number of elements in the multimap.

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

   Swaps the contents of the multimap x with the current multimap, *this.

iterator
upper_bound(const key_type& x);

   Returns an iterator to the first element whose key is less than or equal to
   x. If no such element exists, then end() is returned.

const_iterator
upper_bound(const key_type& x) const;

   Same as upper_bound above but returns a const_iterator.

value_compare
value_comp() const;

   Returns  a  function	 object	 capable  of  comparing value_types (key,value
   pairs) using the comparison operation, Compare, of the current multimap.

NON-MEMBER OPERATORS
       bool
       operator==(const multimap<Key, T, Compare, Allocator>& x,
	  const multimap<Key, T, Compare, Allocator>& y);

   Returns true if all elements in x are element-wise equal to all elements in
   y, using (T::operator==). Otherwise it returns false.

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

   Returns !(x==y).

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

   Returns  true  if x is lexicographically less than y. Otherwise, it returns
   false.

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

   Returns y < x.

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

   Returns !(y < x).

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

   Returns !(x < y).

SPECIALIZED ALGORITHMS
template<;class Key, class T, class Compare, class Allocator>
void swap(multimap<;Key, T, Compare, Allocator>& a,
	  multimap<Key, T, Compare, Allocator>& b);

   Swaps the contents of a and b.

EXAMPLE
//
// multimap.cpp
//
 #include <string>
 #include <map>
 #include <iostream>
using namespace std;

typedef multimap<;int, string, less<int> > months_type;

 // Print out a pair
template <;class First, class Second>
ostream& operator<;<(ostream& out,
		    const pair<First,Second>& p)
 {
  cout << p.second << " has " << p.first << " days";
  return out;
 }

 // Print out a multimap
ostream& operator<;<(ostream& out, months_type l)
 {
  copy(l.begin(),l.end(), ostream_iterator
	     <months_type::value_type,char>(cout,"\n"));
  return out;
 }

int main(void)
 {
   // create a multimap of months and the number of
   // days in the month
  months_type months;

  typedef months_type::value_type value_type;

   // Put the months in the multimap
  months.insert(value_type(31, string("January")));
  months.insert(value_type(28, string("February")));
  months.insert(value_type(31, string("March")));
  months.insert(value_type(30, string("April")));
  months.insert(value_type(31, string("May")));
  months.insert(value_type(30, string("June")));
  months.insert(value_type(31, string("July")));
  months.insert(value_type(31, string("August")));
  months.insert(value_type(30, string("September")));
  months.insert(value_type(31, string("October")));
  months.insert(value_type(30, string("November")));
  months.insert(value_type(31, string("December")));

   // print out the months
  cout << "All months of the year" << endl << months
	<< endl;

   // Find the Months with 30 days
  pair<months_type::iterator,months_type::iterator> p =
	 months.equal_range(30);

   // print out the 30 day months
  cout << endl << "Months with 30 days" << endl;
  copy(p.first,p.second,
       ostream_iterator<months_type::value_type,char>
       (cout,"\n"));

  return 0;
 }

Program Output

All months of the year
February has 28 days
April has 30 days
June has 30 days
September has 30 days
November has 30 days
January has 31 days
March has 31 days
May has 31 days
July has 31 days
August has 31 days
October has 31 days
December has 31 days

Months with 30 days
April has 30 days
June has 30 days
September has 30 days
November has 30 days

WARNINGS
       Member function templates are used in all containers  included  in  the
       Standard	 Template Library. An example of this feature is the construc‐
       tor for multimap<Key,T,Compare,Allocator> that  takes  two  templatized
       iterators:

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

multimap  also	has an insert function of this type. These functions, when not
restricted by compiler limitations, allow you to use any type of input	itera‐
tor  as	 arguments. For compilers that do not support this feature, substitute
functions allow you to use an iterator obtained from the  same	type  of  con‐
tainer	as  the one you are constructing (or calling a member function on), or
you can use a pointer to the type of element you have in the container.

For example, if your compiler does not support member function templates,  you
can construct a multimap in the following two ways:

multimap<;int,int>::value_type intarray[10];
multimap<;int,int> first_map(intarry, intarray + 10);
multimap<;int,int> second_multimap(first_multimap.begin(),
		 first_multimap.end());

but not this way:

multimap<;long,long>
long_multimap(first_multimap.begin(),first_multimap.end());

since the long_multimap and first_multimap are not the same type.

Also,  many  compilers do not support default template arguments. If your com‐
piler is one of these you always need to supply the Compare template  argument
and the Allocator template argument. For instance, you have to write:

multimap<;int, int, less<int>, allocator<int> >

instead of:

multimap<;int, int>

If  your  compiler does not support namespaces, then you do not need the using
declaration for std.

SEE ALSO
       allocator, Containers, Iterators, map

Rogue Wave Software		  02 Apr 1998			multimap(3C++)
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