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wxHashSet Class Reference
Containers

`#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.