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multiset(3C++)			       -			multiset(3C++)

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

NAME
       multiset

	-  An associative container that allows fast access to stored key val‐
       ues. Storage of duplicate keys is allowed. A multiset supports bidirec‐
       tional iterators.

SYNOPSIS
       #include <set>
       template <class Key, class Compare = less<Key>,
	 class Allocator = allocator<Key> >
class multiset;

DESCRIPTION
       multiset_<Key,_Compare,_Allocator>_allows  fast	access	to  stored key
       values. The default operation for key comparison	 is  the  <  operator.
       Insertion of duplicate keys is allowed with a multiset.

       multiset uses bidirectional iterators that point to a stored key.

       Any type used for the template parameter Key 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 Compare = less<Key>,
	 class Allocator = allocator<Key> >
class multiset {

public:

// typedefs

  typedef Key key_type;
  typedef Key value_type;
  typedef Compare key_compare;
  typedef Compare value_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;

// Construct/Copy/Destroy

  explicit multiset (const Compare& = Compare(),
		     const Allocator& = Allocator());
  template <class InputIterator>
   multiset (InputIterator, InputIterator,
	     const Compare& = Compare(),
	     const Allocator& = Allocator());
  multiset (const multiset<Key, Compare, Allocator>&);
   ~multiset ();
  multiset<Key, Compare, Allocator>&
	   operator= (const multiset<Key,
		      Compare, Allocator>&);

// 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 (multiset<Key, Compare, Allocator>&);
  void clear ();

// Observers

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

// Multiset operations

  iterator find (const key_type&) const;
  size_type count (const key_type&) const;
  iterator lower_bound (const key_type&) const;
  iterator upper_bound (const key_type&) const;
  pair<iterator, iterator> equal_range
       (const key_type&) const;
   };

// Non-member Operators

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

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

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

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

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

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

// Specialized Algorithms

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

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

   Constructs  an empty multiset that uses the optional relation comp to order
   keys, if it is supplied, and the allocator alloc for	 all  storage  manage‐
   ment.

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

   Constructs a multiset containing values in the range [first, last).

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

   Creates a new multiset by copying all key values from x.

DESTRUCTORS
       ~multiset();

   Releases any allocated memory for this multiset.

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

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

ALLOCATORS
       allocator_type
       get_allocator() const;

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

ITERATORS
       iterator
       begin();

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

const_iterator
begin();

   Returns a const_iterator pointing to the first element stored in the multi‐
   set.

iterator
end();

   Returns an iterator pointing to the last element stored in the multiset (in
   other words, the off-the-end value).

const_iterator
end();

   Returns a const_iterator pointing to the last element stored in the	multi‐
   set (in other words, the off-the-end value).

reverse_iterator
rbegin();

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

const_reverse_iterator
rbegin();

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

reverse_iterator
rend();

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

const_reverse_iterator
rend();

   Returns a const_reverse_iterator pointing to the last element stored in the
   multiset (in other words, the off-the-end value).

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 multiset with the key value x.

bool
empty() const;

   Returns true if the multiset is empty, false otherwise.

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

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

size_type
erase(const key_type& x);

   Deletes  all elements with the key value x from the multiset, if any exist.
   Returns the number of deleted elements.

void
erase(iterator position);

   Deletes the multiset 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.

void
erase(iterator first, iterator last);

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

iterator
find(const key_type& x) const;

   Searches the multiset for a key value x and returns an iterator to that key
   if  it  is  found.  If  such	 a  value  is not found, the iterator end() is
   returned.

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

   x is inserted into the multiset. 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
   multiset. This insert 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 multiset.

iterator
lower_bound(const key_type& x) const;

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

size_type
max_size() const;

   Returns the maximum possible size of the multiset size_type.

size_type
size() const;

   Returns the number of elements in the multiset.

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

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

iterator
upper_bound(const key_type& x) const;

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

value_compare
value_comp() const;

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

NON-MEMBER OPERATORS
       template <class Key, class Compare, class Allocator>
       operator==(const multiset<Key, Compare, Allocator>& x,
	   const multiset<Key, 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.

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

   Returns !(x==y).

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

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

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

   Returns y < x.

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

   Returns !(y < x).

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

   Returns !(x < y).

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

   Swaps the contents of a and b.

EXAMPLE
//
// multiset.cpp
//
#include <set>
#include <iostream>
using namespace std;

typedef multiset<;int, less<int>, allocator> set_type;

ostream& operator<;<(ostream& out, const set_type& s)
 {
  copy(s.begin(),s.end(),
    ostream_iterator<set_type::value_type,char>(cout," "));
  return out;
 }

int main(void)
 {
   // create a multiset of ints
  set_type  si;
  int  i;

  for (int j = 0; j < 2; j++)
   {
    for(i = 0; i < 10; ++i) {
       // insert values with a hint
      si.insert(si.begin(), i);
     }
   }

   // print out the multiset
  cout << si << endl;

   // Make another int multiset and an empty multiset
  set_type si2, siResult;
  for (i = 0; i < 10; i++)
     si2.insert(i+5);
  cout << si2 << endl;

   // Try a couple of set algorithms
  set_union(si.begin(),si.end(),si2.begin(),si2.end(),
	 inserter(siResult,siResult.begin()));
  cout << "Union:" << endl << siResult << endl;

  siResult.erase(siResult.begin(),siResult.end());
  set_intersection(si.begin(),si.end(),
	 si2.begin(),si2.end(),
	 inserter(siResult,siResult.begin()));
  cout << "Intersection:" << endl << siResult << endl;

  return 0;
 }

Program Output

0 0 1 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8 9 9
5 6 7 8 9 10 11 12 13 14
Union:
0 0 1 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8 9 9 10 11 12 13 14
Intersection:
5 6 7 8 9

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_multiset<Key,_Compare,_Allocator>, which takes two  templatized
       iterators:

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

multiset  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). You
can also 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 multiset in the following two ways:

int intarray[10];
multiset<;int> first_multiset(intarray, intarray +10);
multiset<;int> second_multiset(first_multiset.begin(),
	     first_multiset.end());

but not this way:

multiset<;long>
long_multiset(first_multiset.begin(),first_multiset.end());

since the long_multiset and first_multiset 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:

multiset<;int, less<int>, allocator<int> >

instead of:

multiset<;int>

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

SEE ALSO
       allocator, Containers, Iterators, set

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

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