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Category: containers | | Component type: type |
Description
Hash_multimap
is a HashedAssociativeContainer that associates objects of type Key
with objects of type Data
. Hash_multimap
is a PairAssociativeContainer, meaning that its value type is pair<const Key, Data>
. It is also a MultipleAssociativeContainer, meaning that there is no limit on the number of elements whose keys may compare equal using EqualKey
.
Looking up an element in a hash_multimap
by its key is efficient, so hash_multimap
is useful for "dictionaries" where the order of elements is irrelevant. If it is important for the elements to be in a particular order, however, then Multimap
is more appropriate.
Example
struct eqstr
{
bool operator()(const char* s1, const char* s2) const
{
}
};
typedef hash_multimap<const char*, int, hash<const char*>, eqstr> map_type;
void lookup(const map_type& Map, const char* str)
{
cout << str << ": ";
pair<map_type::const_iterator, map_type::const_iterator> p =
Map.equal_range(str);
for (map_type::const_iterator i = p.first; i != p.second; ++i)
cout << (*i).second << " ";
cout << endl;
}
int main()
{
map_type M;
M.insert(map_type::value_type("H", 1));
M.insert(map_type::value_type("H", 2));
M.insert(map_type::value_type("C", 12));
M.insert(map_type::value_type("C", 13));
M.insert(map_type::value_type("O", 16));
M.insert(map_type::value_type("O", 17));
M.insert(map_type::value_type("O", 18));
M.insert(map_type::value_type("I", 127));
lookup(M, "I");
lookup(M, "O");
lookup(M, "Rn");
}
Definition
Defined in the header hash_map, and in the backward-compatibility header hash_map.h. This class is an SGI extension; it is not part of the C++ standard.
Template parameters
Parameter | Description | Default |
Key | The hash_multimap's key type. This is also defined as hash_multimap::key_type . | |
Data | The hash_multimap's data type. This is also defined as hash_multimap::data_type . | |
HashFcn | The HashFunction used by the hash_multimap. This is also defined as hash_multimap::hasher . | hash<Key> |
EqualKey | The hash_multimap's key equality function: a BinaryPredicate that determines whether two keys are equal. This is also defined as hash_multimap::key_equal . | equal_to<Key> |
Alloc | The hash_set 's allocator, used for all internal memory management. | Allocators |
Model of
MultipleHashedAssociativeContainer, PairAssociativeContainer
Type requirements
Public base classes
None.
Members
Member | Where defined | Description |
key_type | AssociativeContainer | The hash_multimap 's key type, Key . |
data_type | PairAssociativeContainer | The type of object associated with the keys. |
value_type | PairAssociativeContainer | The type of object, pair<const key_type, data_type> , stored in the hash_multimap. |
hasher | HashedAssociativeContainer | The hash_multimap 's HashFunction. |
key_equal | HashedAssociativeContainer | functors that compares keys for equality. |
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 hash_multimap . [1] |
const_iterator | Container | Const iterator used to iterate through a hash_multimap . |
iterator begin() | Container | Returns an iterator pointing to the beginning of the hash_multimap . |
iterator end() | Container | Returns an iterator pointing to the end of the hash_multimap . |
const_iterator begin() const | Container | Returns an const_iterator pointing to the beginning of the hash_multimap . |
const_iterator end() const | Container | Returns an const_iterator pointing to the end of the hash_multimap . |
size_type size() const | Container | Returns the size of the hash_multimap . |
size_type max_size() const | Container | Returns the largest possible size of the hash_multimap . |
bool empty() const | Container | true if the hash_multimap 's size is 0 . |
size_type bucket_count() const | HashedAssociativeContainer | Returns the number of buckets used by the hash_multimap . |
void resize(size_type n) | HashedAssociativeContainer | Increases the bucket count to at least n . |
hasher hash_funct() const | HashedAssociativeContainer | Returns the hasher object used by the hash_multimap . |
key_equal key_eq() const | HashedAssociativeContainer | Returns the key_equal object used by the hash_multimap . |
hash_multimap() | Container | Creates an empty hash_multimap . |
hash_multimap(size_type n) | HashedAssociativeContainer | Creates an empty hash_multimap with at least n buckets. |
hash_multimap(size_type n,
const hasher& h)
| HashedAssociativeContainer | Creates an empty hash_multimap with at least n buckets, using h as the hash function. |
hash_multimap(size_type n,
const hasher& h,
const key_equal& k)
| HashedAssociativeContainer | Creates an empty hash_multimap with at least n buckets, using h as the hash function and k as the key equal function. |
template <class InputIterator>
hash_multimap(InputIterator, InputIterator)
[2] | MultipleHashedAssociativeContainer | Creates a hash_multimap with a copy of a range. |
template <class InputIterator>
hash_multimap(InputIterator, InputIterator,
size_type n)
[2] | MultipleHashedAssociativeContainer | Creates a hash_multimap with a copy of a range and a bucket count of at least n . |
template <class InputIterator>
hash_multimap(InputIterator, InputIterator,
size_type n, const hasher& h)
[2] | MultipleHashedAssociativeContainer | Creates a hash_multimap with a copy of a range and a bucket count of at least n , using h as the hash function. |
template <class InputIterator>
hash_multimap(InputIterator, InputIterator,
size_type n, const hasher& h,
const key_equal& k)
[2] | MultipleHashedAssociativeContainer | Creates a hash_multimap with a copy of a range and a bucket count of at least n , using h as the hash function and k as the key equal function. |
hash_multimap(const hash_multimap&) | Container | The copy constructor. |
hash_multimap& operator=(const hash_multimap&) | Container | The assignment operator |
void swap(hash_multimap&) | Container | Swaps the contents of two hash_multimaps. |
iterator insert(const value_type& x) | MultipleAssociativeContainer | Inserts x into the hash_multimap . |
template <class InputIterator>
void insert(InputIterator, InputIterator)
[2] | MultipleAssociativeContainer | Inserts a range into the hash_multimap . |
void erase(iterator pos) | AssociativeContainer | Erases the element pointed to by pos . |
size_type erase(const key_type& k) | AssociativeContainer | Erases the element whose key is k . |
void erase(iterator first, iterator last) | AssociativeContainer | Erases all elements in a range. |
void clear() | AssociativeContainer | Erases all of the elements. |
const_iterator find(const key_type& k) const | AssociativeContainer | Finds an element whose key is k . |
iterator find(const key_type& k) | AssociativeContainer | Finds an element whose key is k . |
size_type count(const key_type& k) const | AssociativeContainer | Counts the number of elements whose key is k . |
pair<const_iterator, const_iterator>
| AssociativeContainer | Finds a range containing all elements whose key is k . |
| AssociativeContainer | Finds a range containing all elements whose key is k . |
| HashedAssociativeContainer | Tests two hash_multimaps for equality. This is a global function, not a member function. |
New members
All of hash_multimap
's members are defined in the MultipleHashedAssociativeContainer and PairAssociativeContainer requirements. Hash_multimap
does not introduce any new members.
Notes
[1] Hash_multimap::iterator
is not a mutable iterator, because hash_multimap::value_type
is not Assignable. That is, if i
is of type hash_multimap::iterator
and p
is of type hash_multimap::value_type
, then *i = p
is not a valid expression. However, hash_multimap::iterator
isn't a constant iterator either, because it can be used to modify the object that it points to. Using the same notation as above, (i).second = p is a valid expression.
[2] 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 InputIterator. If your compiler does not yet support member templates, though, then the arguments must either be of type const value_type
or of type hash_multimap::const_iterator
.
See also
AssociativeContainer, HashedAssociativeContainer, PairAssociativeContainer, MultipleHashedAssociativeContainer, set
, Map
, multiset
, Multimap
, hash_set
, hash_map
, hash_multiset