## wxHashSet

This is a simple, type-safe, and reasonably efficient hash set class, whose interface is a subset of the interface of STL containers. In particular, the interface is modeled after std::set, and the various, non-standard, std::hash_map.

Example

        class MyClass { /* ... */ };

        // same, with MyClass* keys (only uses pointer equality!)
        WX_DECLARE_HASH_SET( MyClass*, wxPointerHash, wxPointerEqual, MySet1 );
        // same, with int keys
        WX_DECLARE_HASH_SET( int, wxIntegerHash, wxIntegerEqual, MySet2 );
        // declare a hash set with string keys
        WX_DECLARE_HASH_SET( wxString, wxStringHash, wxStringEqual, MySet3 );

        MySet1 h1;
        MySet2 h1;
        MySet3 h3;

        // store and retrieve values
        h1.insert( new MyClass( 1 ) );

        h3.insert( "foo" );
        h3.insert( "bar" );
        h3.insert( "baz" );

        int size = h3.size(); // now is three
        bool has_foo = h3.find( "foo" ) != h3.end();

        h3.insert( "bar" ); // still has size three

        // iterate over all the elements in the class
        MySet3::iterator it;
        for( it = h3.begin(); it != h3.end(); ++it )
        {
            wxString key = *it;
            // do something useful with key
        }

Declaring new hash set types

        WX_DECLARE_HASH_SET( KEY_T,      // type of the keys
                             HASH_T,     // hasher
                             KEY_EQ_T,   // key equality predicate
                             CLASSNAME); // name of the class

The HASH_T and KEY_EQ_T are the types used for the hashing function and key comparison. wxWidgets provides three predefined hashing functions: `wxIntegerHash` for integer types ( `int`, `long`, `short`, and their unsigned counterparts ), `wxStringHash` for strings ( `wxString`, `wxChar*`, `char*` ), and `wxPointerHash` for any kind of pointer. Similarly three equality predicates: `wxIntegerEqual`, `wxStringEqual`, `wxPointerEqual` are provided.

Using this you could declare a hash set using `int` values like this:

        WX_DECLARE_HASH_SET( int,
                             wxIntegerHash,
                             wxIntegerEqual,
                             MySet );

        // using an user-defined class for keys
        class MyKey { /* ... */ };

        // hashing function
        class MyKeyHash
        {
        public:
            MyKeyHash() { }

            unsigned long operator()( const MyKey& k ) const
                { /* compute the hash */ }

            MyKeyHash& operator=(const MyKeyHash&) { return *this; }
        };

        // comparison operator
        class MyKeyEqual
        {
        public:
            MyKeyEqual() { }
            bool operator()( const MyKey& a, const MyKey& b ) const
                { /* compare for equality */ }

            MyKeyEqual& operator=(const MyKeyEqual&) { return *this; }
        };

        WX_DECLARE_HASH_SET( MyKey,      // type of the keys
                             MyKeyHash,  // hasher
                             MyKeyEqual, // key equality predicate
                             CLASSNAME); // name of the class

Types

In the documentation below you should replace wxHashSet with the name you used in the class declaration.

wxHashSet::key_type | Type of the hash keys
wxHashSet::mapped_type | Type of hash keys
wxHashSet::value_type | Type of hash keys
wxHashSet::iterator | Used to enumerate all the elements in a hash set; it is similar to a `value_type*`
wxHashSet::const_iterator | Used to enumerate all the elements in a constant hash set; it is similar to a `const value_type*`
wxHashSet::size_type | Used for sizes
wxHashSet::Insert_Result | The return value for insert()

Iterators

An iterator is similar to a pointer, and so you can use the usual pointer operations: `++it` ( and `it++` ) to move to the next element, `*it` to access the element pointed to, `*it` to access the value of the element pointed to. Hash sets provide forward only iterators, this means that you can't use `--it`, `it + 3`, `it1 - it2`.

Include files

<wx/hashset.h>

Members

wxHashSet::wxHashSet
wxHashSet::begin
wxHashSet::clear
wxHashSet::count
wxHashSet::empty
wxHashSet::end
wxHashSet::erase
wxHashSet::find
wxHashSet::insert
wxHashSet::size

### wxHashSet::wxHashSet

wxHashSet(size_type size = 10)

The size parameter is just a hint, the table will resize automatically to preserve performance.

wxHashSet(const wxHashSet& set)

Copy constructor.

### wxHashSet::begin

const_iterator begin() const

iterator begin()

Returns an iterator pointing at the first element of the hash set. Please remember that hash sets do not guarantee ordering.

### wxHashSet::clear

void clear()

Removes all elements from the hash set.

### wxHashSet::count

size_type count(const key_type& key) const

Counts the number of elements with the given key present in the set. This function returns only 0 or 1.

### wxHashSet::empty

bool empty() const

Returns true if the hash set does not contain any elements, false otherwise.

### wxHashSet::end

const_iterator end() const

iterator end()

Returns an iterator pointing at the one-after-the-last element of the hash set. Please remember that hash sets do not guarantee ordering.

### wxHashSet::erase

size_type erase(const key_type& key)

Erases the element with the given key, and returns the number of elements erased (either 0 or 1).

void erase(iterator it)

void erase(const_iterator it)

Erases the element pointed to by the iterator. After the deletion the iterator is no longer valid and must not be used.

### wxHashSet::find

iterator find(const key_type& key)

const_iterator find(const key_type& key) const

If an element with the given key is present, the functions returns an iterator pointing at that element, otherwise an invalid iterator is returned (i.e. hashset.find( non_existent_key ) == hashset.end()).

### wxHashSet::insert

Insert_Result insert(const value_type& v)

Inserts the given value in the hash set. The return value is equivalent to a `std::pair<wxHashMap::iterator, bool>`; the iterator points to the inserted element, the boolean value is `true` if `v` was actually inserted.

### wxHashSet::size

size_type size() const

Returns the number of elements in the set.