Template class which provides a set implemented as a hash. More...

Classes
class	const_iterator
	Provides an STL style const iterator for QSet More...

class	iterator
	Provides an STL style iterator for QSet More...

Public Typedefs
using	allocator_type = typename std::unordered_set< T, Hash >::allocator_type

using	const_iterator = typename std::unordered_set< T, Hash >::const_iterator

using	const_pointer = typename std::unordered_set< T, Hash >::const_pointer

using	const_reference = typename std::unordered_set< T, Hash >::const_reference

using	difference_type = typename std::unordered_set< T, Hash >::difference_type

using	hasher = typename std::unordered_set< T, Hash >::hasher

using	iterator = typename std::unordered_set< T, Hash >::iterator

using	Java_Iterator = QSetIterator< T >

using	Java_MutableIterator = QMutableSetIterator< T >

using	key_equal = typename std::unordered_set< T, Hash >::key_equal

using	key_type = typename std::unordered_set< T, Hash >::key_type

using	pointer = typename std::unordered_set< T, Hash >::pointer

using	reference = typename std::unordered_set< T, Hash >::reference

using	size_type = typename std::unordered_set< T, Hash >::difference_type

using	value_type = typename std::unordered_set< T, Hash >::value_type

Public Methods
	QSet () = default

	QSet (const QSet< T > &other) = default

template<class Input_Iterator >
	QSet (Input_Iterator first, Input_Iterator last)

	QSet (QSet< T > &&other) = default

	QSet (std::initializer_list< T > args)

iterator	begin ()

const_iterator	begin () const

size_type	capacity () const

const_iterator	cbegin () const

const_iterator	cend () const

void	clear ()

const_iterator	constBegin () const

const_iterator	constEnd () const

const_iterator	constFind (const T &value) const

bool	contains (const QSet< T > &other) const

bool	contains (const T &value) const

size_type	count () const

bool	empty () const

iterator	end ()

const_iterator	end () const

size_type	erase (const key_type &key)

iterator	erase (const_iterator first, const_iterator last)

iterator	erase (const_iterator pos)

iterator	find (const T &value)

const_iterator	find (const T &value) const

iterator	insert (const T &value)

QSet< T > &	intersect (const QSet< T > &other)

bool	intersects (const QSet< T > &other) const

bool	isEmpty () const

bool	operator!= (const QSet< T > &other) const

QSet< T >	operator& (const QSet< T > &other) const

QSet< T > &	operator&= (const QSet< T > &other)

QSet< T > &	operator&= (const T &value)

QSet< T >	operator+ (const QSet< T > &other) const

QSet< T > &	operator+= (const QSet< T > &other)

QSet< T > &	operator+= (const T &value)

QSet< T >	operator- (const QSet< T > &other) const

QSet< T > &	operator-= (const QSet< T > &other)

QSet< T > &	operator-= (const T &value)

QSet< T > &	operator<< (const T &value)

QSet< T > &	operator= (const QSet< T > &other) = default

QSet< T > &	operator= (QSet< T > &&other) = default

bool	operator== (const QSet< T > &other) const

QSet< T >	operator\| (const QSet< T > &other) const

QSet< T > &	operator\|= (const QSet< T > &other)

QSet< T > &	operator\|= (const T &value)

bool	remove (const T &value)

void	reserve (size_type size)

size_type	size () const

void	squeeze ()

QSet< T > &	subtract (const QSet< T > &other)

void	swap (QSet< T > &other)

QList< T >	toList () const

QSet< T > &	unite (const QSet< T > &other)

QList< T >	values () const

Static Public Methods
static QSet< T >	fromList (const QList< T > &list)

Related Functions
These are not member functions
QDataStream &	operator<< (QDataStream &stream, const QSet< T > &set)

QDataStream &	operator>> (QDataStream &stream, QSet< T > &set)

Detailed Description

template<class T>
class QSet< T >

The QSet class is a template class which provides a set implemented as a hash. This container stores values in an unspecified order and provides very fast lookup of the values.

For an overview and comparison of all containers, refer to the documentation for Container Classes. Refer to the section on Time Complexity for a discussion about which operations will be relatively faster or slower for a given container with a size of n.

Constructors

The following code is a simple example showing how to declare a QSet.

QSet<QString> set; // stores QString values

Accessing Elements

To insert a value into the set use insert() as shown below.

set.insert("one");
set.insert("three");
set.insert("seven");

Another way to insert items into the set is to use operator<<().

set << "twelve" << "fifteen" << "nineteen";

To test whether is present in a set use the contains() method.

if (! set.contains("ninety-nine")) {
   // not found
}

Basic Operations

Items can be removed from the set using remove(). There is also a clear() method which removes all items.

Iterators

To navigate through all the values stored in a QSet, you can use an iterator. QSet supports both Java style iterators (QSetIterator and QMutableSetIterator) and STL style iterators (QSet::iterator and QSet::const_iterator).

The following shows how to iterate over a QSet<QWidget *> using a Java style iterator.

QSetIterator<QWidget *> iter(set);
 
while (iter.hasNext()) {
   qDebug() << iter.next();
}

Here is the same code using an STL style iterator.

QSet<QWidget *>::const_iterator i = set.constBegin();
 
while (i != set.constEnd()) {
   qDebug() << *i;
   ++i;
}

QSet is unordered so the iterator sequence can not be assumed to be predictable. If ordering by key is required use a QMap.

To navigate through a QSet you can use a range based for loop.

QSet<QString> set;
 
for (const QString &value : set) {
   qDebug() << value;
}

Constraints on type T

The QSet value type T should be Default Constructible and Copy Constructible to work with all methods of this class. Data types like QObject are not copy constructible and therefore should never be stored in a container. You can however use a pointer to a QObject or any subclass as the type T.

The type T must provide an operator==() method and there needs to be a global qHash() function which returns a hash value for an argument of the key's type. Refer to the QHash documentation for a list of types supported by qHash().

Additional Information

The QSet automatically grows and shrinks to provide fast lookups without wasting memory. You can still control the size of the hash table by calling reserve(), if you already know approximately how many elements the QSet will contain, but this is not necessary to obtain good performance. You can also call capacity() to retrieve the hash table's size.

See also: QFlatMap, QHash, QMap

Member Typedef Documentation

template<class T >

QSet< T >::allocator_type

Typedef for allocator used by the container.

template<class T >

QSet< T >::const_iterator

Typedef for std::unordered_set<T>::const_iterator.

template<class T >

QSet< T >::const_pointer

Typedef for const T *.

template<class T >

QSet< T >::const_reference

Typedef for const T &;.

template<class T >

QSet< T >::difference_type

Typedef for const ptrdiff_t.

template<class T >

QSet< T >::hasher

Typedef for the functor used to hash keys.

template<class T >

QSet< T >::iterator

Typedef for std::unordered_set<T>::iterator.

template<class T >

QSet< T >::Java_Iterator

Typedef for the java style const iterator.

See also: QSetIterator()

template<class T >

QSet< T >::Java_MutableIterator

Typedef for the java style mutable iterator.

See also: QMutableSetIterator()

template<class T >

QSet< T >::key_equal

Typedef for the functor used to compare keys.

template<class T >

QSet< T >::key_type

Typedef for T.

template<class T >

QSet< T >::pointer

Typedef for T *.

template<class T >

QSet< T >::reference

Typedef for T &.

template<class T >

QSet< T >::size_type

Typedef for int.

template<class T >

QSet< T >::value_type

Typedef for T.

Constructor & Destructor Documentation

template<class T >

QSet< T >::QSet ( )

default

Constructs an empty set.

See also: clear()

template<class T >

QSet< T >::QSet ( const QSet< T > & other )

default

Copy constructs a new QSet from other.

template<class T >

QSet< T >::QSet ( QSet< T > && other )

default

Move constructs a new QSet from other.

template<class T >

QSet< T >::QSet ( std::initializer_list< T > args )

inline

Construct a set from the std::initializer_list specified by args.

template<class T >

template<class Input_Iterator >

QSet< T >::QSet	(	Input_Iterator	first,
		Input_Iterator	last
	)

Construct a set containing the elements from first to last.

Method Documentation

template<class T >

iterator QSet< T >::begin ( )

inline

Returns a non-const STL style iterator positioned at the first item in the set.

template<class T >

const_iterator QSet< T >::begin ( ) const

inline

Returns a const STL style iterator positioned at the first item in the set.

See also: constBegin(), end()

template<class T >

size_type QSet< T >::capacity ( ) const

inline

Returns the number of buckets in the set's internal hash table.

The purpose of this method is to provide a means of fine tuning QSet's memory usage. In general, you will rarely ever need to call this method. If you want to know how many items are in the set, call size().

See also: reserve(), squeeze()

template<class T >

const_iterator QSet< T >::cbegin ( ) const

inline

Returns a const STL style iterator positioned at the first item in the set.

See also: cend()

template<class T >

const_iterator QSet< T >::cend ( ) const

inline

Returns a const STL style iterator pointing to the imaginary item after the last item in the set.

See also: cbegin()

template<class T >

void QSet< T >::clear ( )

inline

Removes all elements from this QSet.

See also: remove()

template<class T >

const_iterator QSet< T >::constBegin ( ) const

inline

Returns a const STL style iterator positioned at the first item in the set.

See also: constEnd()

template<class T >

const_iterator QSet< T >::constEnd ( ) const

inline

Returns a const STL style iterator pointing to the imaginary item after the last item in the set.

See also: constBegin()

template<class T >

const_iterator QSet< T >::constFind ( const T & value ) const

inline

Returns a const iterator positioned at the item value in the set. If the set contains no item value, the method returns constEnd().

See also: find(), contains()

template<class T >

bool QSet< T >::contains ( const QSet< T > & other ) const

inline

Returns true if this QSet contains all items from the other set, otherwise returns false.

See also: insert(), remove(), find()

template<class T >

bool QSet< T >::contains ( const T & value ) const

inline

Returns true if this QSet contains item value, otherwise returns false.

See also: insert(), remove(), find()

template<class T >

size_type QSet< T >::count ( ) const

inline

Equivalent to calling size().

template<class T >

bool QSet< T >::empty ( ) const

inline

Returns true if the QSet is empty.

template<class T >

iterator QSet< T >::end ( )

inline

Returns a non-const STL style iterator pointing to the imaginary item after the last item in the set.

template<class T >

const_iterator QSet< T >::end ( ) const

inline

Returns a const STL style iterator positioned at the imaginary item after the last item in the set.

See also: constEnd(), begin()

template<class T >

size_type QSet< T >::erase ( const key_type & key )

inline

Removes every item matching key from this QSet. Returns how many items were removed.

template<class T >

iterator QSet< T >::erase	(	const_iterator	first,
		const_iterator	last
	)

inline

Removes the items between first and last.

template<class T >

iterator QSet< T >::erase ( const_iterator pos )

inline

Removes the item at the iterator position pos from the set, and returns an iterator positioned at the next item in the set.

Unlike remove(), this method never invalidates iterators. This means it can safely be called while iterating and will not affect the order of items in the set.

See also: remove(), find()

template<class T >

iterator QSet< T >::find ( const T & value )

inline

Returns a non-const iterator positioned at the item value in the set. If the set contains no item value, the method returns end().

template<class T >

const_iterator QSet< T >::find ( const T & value ) const

inline

Returns a const iterator positioned at the item value in the set. If the set contains no item value, the method returns constEnd().

See also: constFind(), contains()

template<typename T >

QSet< T > QSet< T >::fromList ( const QList< T > & list )

static

Returns a new QSet object containing the data contained in list. Since QSet does not allow duplicates, the resulting QSet might be smaller than the list, because QList can contain duplicates.

QStringList list;
list << "Julia" << "Mike" << "Mike" << "Julia" << "Julia";
 
QSet<QString> set = QSet<QString>::fromList(list);
set.contains("Julia");  // returns true
set.contains("Mike");   // returns true
set.size();             // returns 2

See also: toList(), QList::toSet()

template<class T >

iterator QSet< T >::insert ( const T & value )

inline

Inserts value into this QSet if the item is not already in this set. Returns an iterator pointing at the inserted item.

See also: operator<<(), remove(), contains()

template<class T >

QSet< T > & QSet< T >::intersect ( const QSet< T > & other )

inline

Removes all items from this QSet which are not contained in the other set. A reference to the modified QSet is returned.

QSet<QString> setA;
setA << "apple" << "banana" << "cherry";
 
QSet<QString> setB;
setB << "banana" << "cherry" << "date";
 
QSet<QString> result = setA.intersect(setB);
 
// setA == { "banana", "cherry" }
// result is equal to setA

See also: operator&=(), unite(), subtract()

template<class T >

bool QSet< T >::intersects ( const QSet< T > & other ) const

inline

Returns true if this QSet has at least one item in common with other.

template<class T >

bool QSet< T >::isEmpty ( ) const

inline

Returns true if the set contains no elements, otherwise returns false.

See also: size()

template<class T >

bool QSet< T >::operator!= ( const QSet< T > & other ) const

inline

Returns true if the other set is not equal to this set, otherwise returns false. Two sets are considered equal if they contain the same elements.

This method requires the type T to support operator==().

See also: operator==()

template<class T >

QSet< T > QSet< T >::operator& ( const QSet< T > & other ) const

inline

Returns a new QSet which is the intersection of this set and other.

See also: intersect(), operator&=(), operator|(), operator-()

template<class T >

QSet< T > & QSet< T >::operator&= ( const QSet< T > & other )

inline

Equivalent to calling intersect(other).

See also: operator&(), operator|=(), operator-=()

template<class T >

QSet< T > & QSet< T >::operator&= ( const T & value )

inline

Removes all elements from this QSet which do not match value.

template<class T >

QSet< T > QSet< T >::operator+ ( const QSet< T > & other ) const

inline

Returns a new QSet which contains the elements from this QSet combined with elements in other.

See also: unite(), operator|=(), operator&(), operator-()

template<class T >

QSet< T > & QSet< T >::operator+= ( const QSet< T > & other )

inline

Equivalent to calling unite(other).

See also: operator|(), operator&=(), operator-=()

template<class T >

QSet< T > & QSet< T >::operator+= ( const T & value )

inline

Inserts value and returns a reference to this QSet. If value already exists QSet is not modified.

See also: insert()

template<class T >

QSet< T > QSet< T >::operator- ( const QSet< T > & other ) const

inline

Returns a new QSet which contains all elements in this QSet and not in other.

See also: subtract(), operator-=(), operator|(), operator&()

template<class T >

QSet< T > & QSet< T >::operator-= ( const QSet< T > & other )

inline

Equivalent to calling subtract(other).

See also: operator-(), operator|=(), operator&=()

template<class T >

QSet< T > & QSet< T >::operator-= ( const T & value )

inline

Removes the given value from this QSet. If the value is not in this QSet nothing is removed. A reference to the modified QSet is returned.

See also: remove()

template<class T >

QSet< T > & QSet< T >::operator<< ( const T & value )

inline

Inserts value and returns a reference to this QSet. If value already exists this set is left unchanged.

See also: insert()

template<class T >

QSet< T > & QSet< T >::operator= ( const QSet< T > & other )

default

Copy assigns from other and returns a reference to this object.

template<class T >

QSet< T > & QSet< T >::operator= ( QSet< T > && other )

default

Move assigns from other and returns a reference to this object.

template<class T >

bool QSet< T >::operator== ( const QSet< T > & other ) const

inline

Returns true if the other set is equal to this set, otherwise returns false. Two sets are considered equal if they contain the same elements.

This method requires the type T to support operator==().

See also: operator!=()

template<class T >

QSet< T > QSet< T >::operator| ( const QSet< T > & other ) const

inline

Returns a new QSet which is the union of this QSet and other.

See also: unite(), operator|=(), operator&(), operator-()

template<class T >

QSet< T > & QSet< T >::operator|= ( const QSet< T > & other )

inline

Equivalent to calling unite(other).

See also: operator|(), operator&=(), operator-=()

template<class T >

QSet< T > & QSet< T >::operator|= ( const T & value )

inline

Inserts value and returns a reference to this QSet. If value already exists this set is left unchanged.

See also: insert()

template<class T >

bool QSet< T >::remove ( const T & value )

inline

Removes any occurrence of value from this QSet. Returns true if an item was actually removed, otherwise returns false.

See also: contains(), insert()

template<class T >

void QSet< T >::reserve ( size_type size )

inline

Ensures the internal hash table consists of at least size buckets. This method is useful for code which needs to build a huge set and wants to avoid repeated reallocation.

Ideally the size should be slightly larger than the maximum number of elements expected in the set. The size does not need to be a prime number because QSet will round up to the nearest prime number. If size is underestimated the worst which can happen is QSet will be a bit slower. In general, you will rarely need to call this method. The QSet internal hash table automatically shrinks or grows to provide good performance without wasting too much memory.

QSet<QString> set;
set.reserve(20000);
 
for (int i = 0; i < 20000; ++i) {
   set.insert(values[i]);
}

See also: squeeze(), capacity()

template<class T >

size_type QSet< T >::size ( ) const

inline

Returns the number of items in this QSet.

See also: isEmpty(), count()

template<class T >

void QSet< T >::squeeze ( )

inline

Reduces the size of the internal hash table to save memory. The purpose of this method is to provide a means to fine tune the internal data structure memory usage. In general calling this method is rarely required.

See also: reserve(), capacity()

template<class T >

QSet< T > & QSet< T >::subtract ( const QSet< T > & other )

inline

Removes all items from this QSet which are contained in other. A reference to the modified QSet is returned.

See also: operator-=(), unite(), intersect()

template<class T >

void QSet< T >::swap ( QSet< T > & other )

inline

Swaps set other with this QSet. This operation is very fast and never fails.

template<class T >

QList< T > QSet< T >::toList ( ) const

Returns a new QList containing the elements in the set. The order of the elements in the QList is undefined.

QSet<QString> set;
set << "red" << "green" << "blue" << ... << "black";
 
QList<QString> list = set.toList();
std::sort(list.begin(), list.end());

See also: fromList(), QList::fromSet()

template<class T >

QSet< T > & QSet< T >::unite ( const QSet< T > & other )

inline

Each item in other which is not currently in this QSet, will be added. A reference to the modified QSet is returned.

See also: operator|=(), intersect(), subtract()

template<class T >

QList< T > QSet< T >::values ( ) const

inline

Returns a new QList containing the elements in this Qet. The order of the elements in the QList is undefined.

Equivalent to calling toList().

See also: fromList(), QList::fromSet()

Friends And Related Function Documentation

QDataStream & operator<<	(	QDataStream &	stream,
		const QSet< T > &	set
	)

Refer to Serializing Data Types for additional information.

QDataStream & operator>>	(	QDataStream &	stream,
		QSet< T > &	set
	)

Refer to Serializing Data Types for additional information.

Classes

Public Typedefs

Public Methods

Static Public Methods

Related Functions

Detailed Description

template<class T> class QSet< T >

Constructors

Accessing Elements

Basic Operations

Iterators

Constraints on type T

Additional Information

Member Typedef Documentation

Constructor & Destructor Documentation

Method Documentation

Friends And Related Function Documentation

template<class T>
class QSet< T >