wxHashSet Class Reference

#include <wx/hashset.h>

Detailed Description

This is a simple, type-safe, and reasonably efficient hash set class, whose interface is a subset of the interface of STL containers.

The interface is similar to std::tr1::hash_set or std::set classes but notice that, unlike std::set, the contents of a hash set is not sorted.

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.

Library:  wxBase

Category:  Containers

Public Member Functions
	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.
void	clear ()
	Removes all elements from the hash set.
size_type	count (const key_type &key) const
	Counts the number of elements with the given key present in the set.
bool	empty () const
	Returns true if the hash set does not contain any elements, false otherwise.
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).
Insert_Result	insert (const value_type &v)
	Inserts the given value in the hash set.
size_type	size () const
	Returns the number of elements in the set.
const_iterator	begin () const
	Returns an iterator pointing at the first element of the hash set.
iterator	begin ()
	Returns an iterator pointing at the first element of the hash set.
const_iterator	end () const
	Returns an iterator pointing at the one-after-the-last element of the hash set.
iterator	end ()
	Returns an iterator pointing at the one-after-the-last element of the hash set.
void	erase (iterator it)
	Erases the element pointed to by the iterator.
void	erase (const_iterator it)
	Erases the element pointed to by the iterator.
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.
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.

Constructor & Destructor Documentation

wxHashSet::wxHashSet

(

size_type

size = 10

)

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

wxHashSet::wxHashSet

(

const wxHashSet &

set

)

Copy constructor.

Member Function Documentation

const_iterator wxHashSet::begin

(

)

const

Returns an iterator pointing at the first element of the hash set.

Please remember that hash sets do not guarantee ordering.

iterator wxHashSet::begin

(

)

Returns an iterator pointing at the first element of the hash set.

Please remember that hash sets do not guarantee ordering.

void wxHashSet::clear

(

)

Removes all elements from the hash set.

size_type wxHashSet::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.

bool wxHashSet::empty

(

)

const

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

const_iterator wxHashSet::end

(

)

const

Returns an iterator pointing at the one-after-the-last element of the hash set.

Please remember that hash sets do not guarantee ordering.

iterator wxHashSet::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.

size_type wxHashSet::erase

(

const key_type &

key

)

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

void wxHashSet::erase

(

iterator

it

)

Erases the element pointed to by the iterator.

After the deletion the iterator is no longer valid and must not be used.

void wxHashSet::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.

iterator wxHashSet::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()

const_iterator wxHashSet::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()

Insert_Result wxHashSet::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.

size_type wxHashSet::size

(

)

const

Returns the number of elements in the set.