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** QValueVector class documentation
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/*****************************************************************************
  QValueVector documentation
 *****************************************************************************/

/*!
  \class QValueVector qvaluevector.h
  \brief The QValueVector class is a value-based template class that provides a dynamic array.

  \ingroup qtl
  \ingroup tools
  \ingroup shared
  \mainclass
  
  QValueVector is a Qt implementation of an STL-like vector container.  It
  can be used in your application if the standard \c vector is not
  available.  QValueVector is part of the \link qtl.html  Qt Template
  Library\endlink.

  QValueVector\<T\> defines a template instance to create
  a vector of values that all have the class T. Please note that
  QValueVector does not store pointers to the
  members of the vector; it holds a copy of every member. QValueVector
  is said to be value based; in contrast, QPtrList and QDict are pointer
  based.

  QValueVector contains and manages a collection of objects of type T
  and provides random access iterators that allow the contained
  objects to be addressed.  QValueVector owns the contained elements.
  For more relaxed ownership semantics, see QPtrCollection and friends
  which are pointer-based containers.

  QValueVector provides good performance if you append or remove
  elements from the end of the vector.  If you insert or remove
  elements from anywhere but the end, performance is very bad.  The
  reason for this is that elements will need to be copied into new
  positions.

  Some classes cannot be used within a QValueVector - for example, all classes
  derived from QObject and thus all classes that implement widgets.
  Only values can be used in a QValueVector. To qualify as a value the class
  must provide:

  \list
  \i A copy constructor
  \i An assignment operator
  \i A default constructor, i.e., a constructor that does not take any arguments.
  \endlist

  Note that C++ defaults to field-by-field assignment operators and
  copy constructors if no explicit version is supplied. In many cases
  this is sufficient.

  QValueVector uses an STL-like syntax to manipulate and address the
  objects it contains. See \link qtl.html this document\endlink for
  more information.

  Example:
  \code
    #include <qvaluevector.h>
    #include <qstring.h>
    #include <stdio.h>

    class Employee
    {
    public:
	Employee(): s(0) {}
	Employee( const QString& name, int salary )
	    : n(name), s(salary)
	{}

	QString     name()   const	 	{ return n; }
	int	    salary() const	 	{ return s; }
	void	    setSalary( int salary )	{ s = salary; }
    private:
	QString     n;
	int         s;
    };

    int main()
    {
	typedef QValueVector<Employee> EmployeeVector;
	EmployeeVector vec( 4 );	// vector of 4 Employees

	vec[0] = Employee("Bill", 50000);
	vec[1] = Employee("Steve",80000);
	vec[2] = Employee("Ron",  60000);

	Employee joe( "Joe", 50000 );
	vec.push_back( joe );
	joe.setSalary( 4000 );
	
	EmployeeVector::iterator it;
	for( it = vec.begin(); it != vec.end(); ++it )
	    printf( "%s earns %d\n", (*it).name().latin1(), (*it).salary() );

	return 0;
    }
  \endcode

  Program output:
  \code
	Bill earns 50000
	Steve earns 80000
	Ron earns 60000
	Joe earns 50000
  \endcode

  As you can see, the latest changes to Joe's salary did not affect the value
  in the vector because the vector created a copy of Joe's entry.

  Many Qt functions return const value vectors; to iterate over these
  you should make a copy and iterate over the copy.

  There are several ways to find items in the vector.  The begin() and
  end() functions return iterators to the beginning and end of the
  vector.  The advantage of getting an iterator is that you can now move
  forward or backward from this position by incrementing/decrementing
  the iterator.  The iterator returned by end() points to the element
  which is one past the last element in the container. The
  past-the-end iterator is still associated with the vector it belongs
  to, however it is \e not dereferenceable; operator*() will not
  return a well-defined value. If the vector is empty(), the iterator
  returned by begin() will equal the iterator returned by end().

  The fastest way to access an element of a vector is by using
  operator[].  This function provides random access and will return a
  reference to the element located at the specified index.  Thus, you
  can access every element directly, in constant time, providing you
  know the location of the element.  It is undefined to access an
  element that does not exist (your application will probably crash).
  For example:

\code
  QValueVector<int> vec1;  // an empty vector
  vec1[10] = 4;  // WARNING: undefined, probably a crash

  QValueVector<QString> vec2(25); // initialize with 25 elements
  vec2[10] = "Dave";  // OK
\endcode

  Whenever inserting, removing or referencing elements in a vector,
  always make sure you are referring to valid positions.  For example:

\code
  void func( QValueVector<int>& vec )
  {
      if ( vec.size() > 10 ) {
          vec[9] = 99; // OK
      }
  };
\endcode

  The iterators provided by vector are random access iterators,
  therefore you can use them with many generic algorithms, for
  example, algorithms provided by the STL or the \link qtl.html QTL\endlink.  

  Another way to find an element in the vector is by using the
  std::find() or \link qtl.html#qFind qFind()\endlink
  algorithms.  For example:

\code
  QValueVector<int> vec;
  ...
  QValueVector<int>::const_iterator it = qFind( vec.begin(), vec.end(), 3 );
  if ( it != vector.end() )
      // 'it' points to the found element
\endcode

  It is safe to have multiple iterators on the vector at the same time.
  Since QValueVector manages memory dynamically, all iterators can
  become invalid if a memory reallocation occurs.  For example, if
  some member of the vector is removed, iterators that point to the
  removed element and to all following elements become
  invalidated. Inserting into the middle of the vector will
  invalidate all iterators.  For convenience, the function back()
  returns a reference to the last element in the vector, and front()
  one for the first.  If the vector is empty(), both back() and front()
  have undefined behavior (your application will crash or do
  unpredictable things).  Use back() and front() with caution, for
  example:

\code
  QValueVector<int> vec( 3 );
  vec.push_back( 1 );
  vec.push_back( 2 );
  vec.push_back( 3 );
  ...
  if ( !vec.empty() ) {
      // OK: modify the first element
      int& i = vec.front();
      i = 18;
  }
  ...
  QValueVector<double> dvec;
  double d = dvec.back(); // undefined behavior
\endcode

  Because QValueVector manages memory dynamically, it is recommended
  to contruct a vector with an initial size.  Inserting and removing
  elements happens fastest when:

\list
	\i Inserting or removing elements happens at the end() of the vector
	\i The vector does not need to allocate additional memory
\endlist

  By creating a QValueVector with a sufficiently large initial size,
  there will be less memory allocations.  Do not use an initial size
  that is too big, since it will still take time to construct all the
  empty entries, and the extra space may be wasted if it is never
  used.

  Because QValueVector is value-based there is no need to be careful about
  deleting elements in the vector. The vector holds its own copies and
  will free them if the corresponding member or the vector itself is
  deleted. You can force the vector to free all of its items with
  clear().

  QValueVector is shared implicitly, which means it can be copied in
  constant time. If multiple QValueVector instances share the same data
  and one needs to modify its contents, this modifying instance makes
  a copy and modifies its private copy; it thus does not affect the
  other instances.  This is often called "copy on write".  If a
  QValueVector is being used in a multi-threaded program, you must
  protect all access to the vector.  See QMutex.

  There are several ways to insert elements into the vector.  The
  push_back() function insert elements into the end of the vector. The
  insert() can be used to add elements at specific positions within
  the vector (normally, inserting elements at the end() of the vector is
  fastest).

  Items can be also be removed from the vector in several ways. There
  are several variants of the erase() function which removes a
  specific element, or range of elements, from the vector.

  Vectors can be also sorted with various STL algorithms , or it can
  be sorted using the \link qtl.html Qt Template Library\endlink.  For
  example with qBubbleSort():

  Example:
  \code
    QValueVector<int> v( 4 );
    v.push_back( 5 );
    v.push_back( 8 );
    v.push_back( 3 );
    v.push_back( 4 );
    qBubbleSort( v );
  \endcode

  QValueVector stores its elements in contiguous memory.  This means
  that you can use a QValueVector in any situation that requires an
  array.  
*/

/*! \enum QValueVector::value_type 
	The type of the object stored in the vector. */
/*! \enum QValueVector::pointer 
	The pointer to T type. */
/*! \enum QValueVector::const_pointer 
	The const pointer to T type. */
/*! \enum QValueVector::iterator 
	The vector's iterator type. */
/*! \enum QValueVector::const_iterator 
	The vector's const iterator type. */
/*! \enum QValueVector::reference 
	The reference to T type. */
/*! \enum QValueVector::const_reference 
	The const reference to T type. */
/*! \enum QValueVector::size_type 
	An unsigned integral type, used to represent various sizes. */
/*! \enum QValueVector::difference_type 
	A signed integral type used to represent the distance between two iterators. */


/*! \fn QValueVector::QValueVector()

  Constructs an empty vector without any elements.  To create a vector
  which reserves an initial amount of space for elements, use \c
  QValueVector(size_type n).  
*/

/*! \fn QValueVector::QValueVector( const QValueVector<T>& v )

  Constructs a copy of \a v.

  This operation costs O(1) time because QValueVector is shared
  implicitly.

  The first modification to the vector does however take O(n) time.
*/

/*! \fn QValueVector::QValueVector( std::vector<T>& v )

  Constructs a copy of \a v.

  This operation costs O(n) time because \a v is copied.
*/

/*! \fn QValueVector::QValueVector( size_type n, const T& val )

  Constructs a vector with an initial size of \a n elements.  Each
  element is initialized with the value of \a val.
*/

/*! \fn QValueVector::~QValueVector()

  Destroys the vector, destroying all elements and freeing the memory.
  References to the values in the vector and all iterators of this
  vector become invalidated. Note that it is impossible for an
  iterator to check whether or not it is valid - QValueVector is
  tuned for performance, not error checking.
*/

/*! \fn QValueVector<T>& QValueVector::operator=( const QValueVector<T>& v )

  Assigns \a v to this vector and returns a reference to this vector.

  All iterators of the current vector become invalidated by this operation.
  The cost of such an assignment is O(1) since QValueVector is implicitly
  shared.
*/

/*! \overload QValueVector<T>& QValueVector::operator=( const std::vector<T>& v )

  Assigns \a v to this vector and returns a reference to this vector.

  All iterators of the current vector become invalidated by this operation.
  The cost of this assignment is O(n) since \a v is copied.
*/

/*! \fn size_type QValueVector::size() const
  Returns the number of elements in the vector.
*/

/*! \fn bool QValueVector::empty() const
  Returns TRUE if the vector is empty, otherwise FALSE.  Equivalent to
  size()==0, but is faster.
*/

/*! \fn size_type QValueVector::capacity() const
  Returns the maximum number of elements possible without memory
  reallocation.  If memory reallocation takes place, some or all
  iterators may become invalidated.
*/

/*! \fn iterator QValueVector::begin()
  Returns an iterator pointing to the beginning of the vector.  If the
  vector is empty(), the returned iterator will equal end().
*/

/*! \fn const_iterator QValueVector::begin() const
    \overload
  Returns a const iterator pointing to the beginning of the vector.
  If the vector is empty(), the returned iterator will equal end().
*/

/*! \fn iterator QValueVector::end()
  Returns an iterator pointing behind the last element of the vector.
*/

/*! \fn const_iterator QValueVector::end() const
    \overload
  Returns a const iterator pointing behind the last element of the vector.
*/

/*! \fn reference QValueVector::at( size_type i , bool* ok )
  Returns a reference to the element with index \a i.  If \a ok is
  non-null, and the index \a i is out of range, *\a ok is set to FALSE
  and the returned reference is undefined.  If the index \a i is
  within the range of the vector, and \a ok is non-null, *\a ok is set to
  TRUE and the returned reference is well defined.
*/

/*! \fn const_reference QValueVector::at( size_type i , bool* ok ) const
    \overload
  Returns a const reference to the element with index \a i.  If \a ok is
  non-null, and the index \a i is out of range, *\a ok is set to FALSE
  and the returned reference is undefined.  If the index \a i is
  within the range of the vector, and \a ok is non-null, *\a ok is set to
  TRUE and the returned reference is well defined.
*/

/*! \fn reference QValueVector::operator[]( size_type i )
  Returns a reference to the element at index \a i.  If \a i is out of
  range, this function has undefined behavior.
*/

/*! \fn const_reference QValueVector::operator[]( size_type i ) const
    \overload
  Returns a const reference to the element at index \a i.  If \a i is out of
  range, this function has undefined behavior.
*/

/*! \fn reference QValueVector::front()
  Returns a reference to the first element in the vector.  If there is
  no first element, this function has undefined behavior.  
*/

/*! \fn const_reference QValueVector::front() const
    \overload
  Returns a const reference to the first element in the vector.  If there is
  no first element, this function has undefined behavior.  
*/

/*! \fn reference QValueVector::back()
  Returns a reference to the last element in the vector.  If there is
  no last element, this function has undefined behavior.  
*/

/*! \fn const_reference QValueVector::back() const
    \overload
  Returns a const reference to the last element in the vector.  If there is
  no last element, this function has undefined behavior.  
*/

/*! \fn void QValueVector::push_back( const T& x )
  Appends a copy of \a x to the end of the vector.
*/

/*! \fn void QValueVector::pop_back()
  Removes the last element from the vector.
*/

/*! \fn iterator QValueVector::insert( iterator pos, const T& x )
  Inserts a copy of \a x at the position immediately before \a pos.
*/

/*! \fn iterator QValueVector::insert( iterator pos, size_type n, const T& x )
    \overload
  Inserts \a n copies of \a x immediately before position x.
*/

/*! \fn void QValueVector::reserve( size_type n )
  Increases the vector's capacity.  If \a n is less than or equal to
  capacity(), nothing happens.  Otherwise, additional memory is
  allocated so that capacity() will be increased to a value greater
  than or equal to \a n.  All iterators will then become invalidated.
  Note that the vector's size() and the values of existing elements
  remain unchanged.
*/

/*! \fn void QValueVector::resize( size_type n, const T& val = T() )
  Changes the size of the vector to \a n.  If n is greater than the
  current size(), elements are added to the end and initialized with
  the value of \a val.  If \a n is less than size(), elements are
  removed from the end.  If \a n is equal to size() nothing happens.
*/

/*! \fn void QValueVector::clear()
  Removes all elements from the vector.
*/

/*! \fn iterator QValueVector::erase( iterator pos )
  Removes the element at position \a pos and returns the position of
  the next element.
*/

/*! \fn iterator QValueVector::erase( iterator first, iterator last )
    \overload
  Removes all elements from \a first up to but not including \a last
  and returns the position of the next element.
*/

/*! \fn bool QValueVector::operator==( const QValueVector<T>& x ) const
  Returns TRUE if each element in this vector equals each
  corresponding element in \a x; otherwise returns FALSE.
*/

/*! \overload bool QValueVector::operator==( const QValueVector<T>& x ) 
  Returns TRUE if each element in this vector equals each
  corresponding element in \a x; otherwise returns FALSE.
*/


/*!
  \fn void QValueVector::detach()
  If the vector does not share its data with another QValueVector instance, nothing
  happens. Otherwise the function creates a new copy of this data and detaches
  from the shared one. This function is called whenever the vector is modified.
  The implicit sharing mechanism is implemented this way.
*/