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Standard C++ Library
Copyright 1998, Rogue Wave Software, Inc.
NAME
multiset
- An associative container that allows fast access to
stored key values. Storage of duplicate keys is allowed. A
multiset supports bidirectional 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 rela-
tion comp to order keys, if it is supplied, and the allo-
cator alloc for all storage management.
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 con-
tents 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 multiset.
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 multiset (in other words, the off-the-end
value).
reverse_iterator
rbegin();
Returns a reverse_iterator pointing to the first element
stored in the multiset. "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 multiset (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 mul-
tiset, if any exist. Returns the number of deleted ele-
ments.
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 mul-
tiset 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 sup-
plied 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 approxi-
mately O(N*log(size()+N)) time.
key_compare
key_comp() const;
Returns a function object capable of comparing key values
using the comparison 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 comparison 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. Oth-
erwise, 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 constructor
for_multiset<Key,_Compare,_Allocator>, which takes two tem-
platized 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 iterator as arguments.
For compilers that do not support this feature, substitute
functions allow you to use an iterator obtained from the
same type of container 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 func-
tion templates, you can construct a multiset in the follow-
ing 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 argu-
ments. If your compiler is one of these you always need to
supply the Compare template argument and the Allocator tem-
plate 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
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