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multiset<Key, Compare, Alloc>


Category: containers 
Component type: type 
Description
Multiset is a
Sorted Associative Container
that stores objects of type Key.
Multiset is a
Simple Associative Container,
meaning that its value type, as well as its key type,
is Key. It is also a
Multiple Associative Container,
meaning that two or more elements may be identical.
Set and multiset
are particularly well suited to the set algorithms
includes,
set_union,
set_intersection,
set_difference, and
set_symmetric_difference.
The reason for this is twofold. First, the set algorithms require
their arguments to be sorted ranges, and, since
set and multiset are
Sorted Associative Containers,
their elements are always sorted in ascending order.
Second, the output range of these algorithms is always sorted, and
inserting a sorted range into a set or multiset is a
fast operation: the
Unique Sorted Associative Container
and Multiple Sorted Associative Container
requirements guarantee that inserting a
range takes only linear time if the range is already sorted.
Multiset has the important property that inserting a new element
into a multiset does not invalidate iterators that point to existing
elements. Erasing an element from a multiset also does not invalidate
any iterators, except, of course, for iterators that actually point
to the element that is being erased.
Example
int main()
{
const int N = 10;
int a[N] = {4, 1, 1, 1, 1, 1, 0, 5, 1, 0};
int b[N] = {4, 4, 2, 4, 2, 4, 0, 1, 5, 5};
multiset<int> A(a, a + N);
multiset<int> B(b, b + N);
multiset<int> C;
cout << "Set A: ";
copy(A.begin(), A.end(), ostream_iterator<int>(cout, " "));
cout << endl;
cout << "Set B: ";
copy(B.begin(), B.end(), ostream_iterator<int>(cout, " "));
cout << endl;
cout << "Union: ";
set_union(A.begin(), A.end(), B.begin(), B.end(),
ostream_iterator<int>(cout, " "));
cout << endl;
cout << "Intersection: ";
set_intersection(A.begin(), A.end(), B.begin(), B.end(),
ostream_iterator<int>(cout, " "));
cout << endl;
set_difference(A.begin(), A.end(), B.begin(), B.end(),
inserter(C, C.begin()));
cout << "Set C (difference of A and B): ";
copy(C.begin(), C.end(), ostream_iterator<int>(cout, " "));
cout << endl;
}
Definition
Defined in the standard header set, and in the nonstandard
backwardcompatibility header multiset.h.
Template parameters
Parameter

Description

Default

Key

The set's key type and value type. This is also defined as multiset::key_type
and multiset::value_type


Compare

The key comparison function, a Strict Weak Ordering whose
argument type is key_type; it returns true if its first
argument is less than its second argument, and false otherwise.
This is also defined as multiset::key_compare and multiset::value_compare.

less<Key>

Alloc

The multiset's allocator, used for all internal memory management.

alloc

Model of
Multiple Sorted Associative Container,
Simple Associative Container
Type requirements
Public base classes
None.
Members
Member

Where defined

Description

value_type

Container

The type of object, T, stored in the multiset.

key_type

Associative Container

The key type associated with value_type.

key_compare

Sorted Associative Container

Function object that compares two keys for ordering.

value_compare

Sorted Associative Container

Function object that compares two values for ordering.

pointer

Container

Pointer to T.

reference

Container

Reference to T

const_reference

Container

Const reference to T

size_type

Container

An unsigned integral type.

difference_type

Container

A signed integral type.

iterator

Container

Iterator used to iterate through a multiset.

const_iterator

Container

Const iterator used to iterate through a multiset. (Iterator and
const_iterator are the same type.)

reverse_iterator

Reversible Container

Iterator used to iterate backwards through a multiset.

const_reverse_iterator

Reversible Container

Const iterator used to iterate backwards through a multiset.
(Reverse_iterator and const_reverse_iterator are the same type.)

iterator begin() const

Container

Returns an iterator pointing to the beginning of the multiset.

iterator end() const

Container

Returns an iterator pointing to the end of the multiset.

reverse_iterator rbegin() const

Reversible Container

Returns a reverse_iterator pointing to the beginning of the
reversed multiset.

reverse_iterator rend() const

Reversible Container

Returns a reverse_iterator pointing to the end of the
reversed multiset.

size_type size() const

Container

Returns the size of the multiset.

size_type max_size() const

Container

Returns the largest possible size of the multiset.

bool empty() const

Container

true if the multiset's size is 0.

key_compare key_comp() const

Sorted Associative Container

Returns the key_compare object used by the multiset.

value_compare value_comp() const

Sorted Associative Container

Returns the value_compare object used by the multiset.

multiset()

Container

Creates an empty multiset.

multiset(const key_compare& comp)

Sorted Associative Container

Creates an empty multiset, using comp as the key_compare object.

template <class InputIterator>
multiset(InputIterator f, InputIterator l)
[1]

Multiple Sorted Associative Container

Creates a multiset with a copy of a range.

template <class InputIterator>
multiset(InputIterator f, InputIterator l,
const key_compare& comp)
[1]

Multiple Sorted Associative Container

Creates a multiset with a copy of a range, using comp as the key_compare
object.

multiset(const multiset&)

Container

The copy constructor.

multiset& operator=(const multiset&)

Container

The assignment operator

void swap(multiset&)

Container

Swaps the contents of two multisets.

iterator insert(const value_type& x)

Multiple Associative Container

Inserts x into the multiset.

iterator insert(iterator pos,
const value_type& x)

Multiple Sorted Associative Container

Inserts x into the multiset, using pos as a hint to where it will be
inserted.

template <class InputIterator>
void insert(InputIterator, InputIterator)
[1]

Multiple Sorted Associative Container

Inserts a range into the multiset.

void erase(iterator pos)

Associative Container

Erases the element pointed to by pos.

size_type erase(const key_type& k)

Associative Container

Erases the element whose key is k.

void erase(iterator first, iterator last)

Associative Container

Erases all elements in a range.

void clear()

Associative Container

Erases all of the elements.

iterator find(const key_type& k) const

Associative Container

Finds an element whose key is k.

size_type count(const key_type& k) const

Associative Container

Counts the number of elements whose key is k.

iterator lower_bound(const key_type& k) const

Sorted Associative Container

Finds the first element whose key is not less than k.

iterator upper_bound(const key_type& k) const

Sorted Associative Container

Finds the first element whose key greater than k.

pair<iterator, iterator>
equal_range(const key_type& k) const

Sorted Associative Container

Finds a range containing all elements whose key is k.

bool operator==(const multiset&,
const multiset&)

Forward Container

Tests two multisets for equality. This is a global function, not
a member function.

bool operator<(const multiset&,
const multiset&)

Forward Container

Lexicographical comparison. This is a global function, not
a member function.

New members
All of multiset's members are defined in the
Multiple Sorted Associative Container and
Simple Associative Container
requirements.
Multiset does not introduce any new members.
Notes
[1]
This member function relies on member template functions, which
at present (early 1998) are not supported by all compilers. If your
compiler supports member templates, you can call this function with
any type of input iterator. If your
compiler does not yet support member templates, though, then the
arguments must either be of type const value_type* or of type
multiset::const_iterator.
See also
Associative Container,
Sorted Associative Container,
Simple Associative Container,
Multiple Sorted Associative Container,
set,
map,
multimap,
hash_set,
hash_map,
hash_multiset,
hash_multimap
Copyright ©
1999 Silicon Graphics, Inc. All Rights Reserved.
TrademarkInformation
