Category: containers | Component type: type |
Hash_set is useful in applications where it is important to be able to search for an element quickly. If it is important for the elements to be in a particular order, however, then set is more appropriate.
struct eqstr { bool operator()(const char* s1, const char* s2) const { return strcmp(s1, s2) == 0; } }; void lookup(const hash_set<const char*, hash<const char*>, eqstr>& Set, const char* word) { hash_set<const char*, hash<const char*>, eqstr>::const_iterator it = Set.find(word); cout << word << ": " << (it != Set.end() ? "present" : "not present") << endl; } int main() { hash_set<const char*, hash<const char*>, eqstr> Set; Set.insert("kiwi"); Set.insert("plum"); Set.insert("apple"); Set.insert("mango"); Set.insert("apricot"); Set.insert("banana"); lookup(Set, "mango"); lookup(Set, "apple"); lookup(Set, "durian"); }
Parameter | Description | Default |
---|---|---|
Key | The hash_set's key type and value type. This is also defined as hash_set::key_type and hash_set::value_type | |
HashFcn | The Hash Function used by the hash_set. This is also defined as hash_set::hasher. | hash<Key> |
EqualKey | The hash_set's key equality function: a binary predicate that determines whether two keys are equal. This is also defined as hash_set::key_equal. | equal_to<Key> |
Alloc | The hash_set's allocator, used for all internal memory management. | alloc |
Member | Where defined | Description |
---|---|---|
value_type | Container | The type of object, T, stored in the hash_set. |
key_type | Associative Container | The key type associated with value_type. |
hasher | Hashed Associative Container | The hash_set's Hash Function. |
key_equal | Hashed Associative Container | Function object 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_set. |
const_iterator | Container | Const iterator used to iterate through a hash_set. (Iterator and const_iterator are the same type.) |
iterator begin() const | Container | Returns an iterator pointing to the beginning of the hash_set. |
iterator end() const | Container | Returns an iterator pointing to the end of the hash_set. |
size_type size() const | Container | Returns the size of the hash_set. |
size_type max_size() const | Container | Returns the largest possible size of the hash_set. |
bool empty() const | Container | true if the hash_set's size is 0. |
size_type bucket_count() const | Hashed Associative Container | Returns the number of buckets used by the hash_set. |
void resize(size_type n) | Hashed Associative Container | Increases the bucket count to at least n. |
hasher hash_funct() const | Hashed Associative Container | Returns the hasher object used by the hash_set. |
key_equal key_eq() const | Hashed Associative Container | Returns the key_equal object used by the hash_set. |
hash_set() | Container | Creates an empty hash_set. |
hash_set(size_type n) | Hashed Associative Container | Creates an empty hash_set with at least n buckets. |
hash_set(size_type n, const hasher& h) |
Hashed Associative Container | Creates an empty hash_set with at least n buckets, using h as the hash function. |
hash_set(size_type n, const hasher& h, const key_equal& k) |
Hashed Associative Container | Creates an empty hash_set with at least n buckets, using h as the hash function and k as the key equal function. |
template <class InputIterator> hash_set(InputIterator f, InputIterator l) [1] |
Unique Hashed Associative Container | Creates a hash_set with a copy of a range. |
template <class InputIterator> hash_set(InputIterator f, InputIterator l, size_type n) [1] |
Unique Hashed Associative Container | Creates a hash_set with a copy of a range and a bucket count of at least n. |
template <class InputIterator> hash_set(InputIterator f, InputIterator l, size_type n, const hasher& h) [1] |
Unique Hashed Associative Container | Creates a hash_set with a copy of a range and a bucket count of at least n, using h as the hash function. |
hash_set(InputIterator f, InputIterator l, size_type n, const hasher& h, const key_equal& k) [1] |
Unique Hashed Associative Container | Creates a hash_set 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_set(const hash_set&) | Container | The copy constructor. |
hash_set& operator=(const hash_set&) | Container | The assignment operator |
void swap(hash_set&) | Container | Swaps the contents of two hash_sets. |
pair<iterator, bool> insert(const value_type& x) |
Unique Associative Container | Inserts x into the hash_set. |
template <class InputIterator> void insert(InputIterator f, InputIterator l) [1] |
Unique Associative Container | Inserts a range into the hash_set. |
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. |
iterator find(const key_type& k) const | Associative Container | Finds an element whose key is k. |
size_type count(const key_type& k) const | Unique Associative Container | Counts the number of elements whose key is k. |
pair<iterator, iterator> equal_range(const key_type& k) const |
Associative Container | Finds a range containing all elements whose key is k. |
bool operator==(const hash_set&, const hash_set&) |
Hashed Associative Container | Tests two hash_sets for equality. This is a global function, not a member function. |
[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 hash_set::const_iterator.