qlist.doc

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/****************************************************************************
** $Id: qt/doc/qlist.doc   2.3.1   edited 2001-01-26 $
**
** QList and QListIterator class documentation
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/*****************************************************************************
  QList documentation
 *****************************************************************************/

/*!
  \class QList qlist.h
  \brief The QList class is a template class that provides doubly linked lists.

  \ingroup collection
  \ingroup tools

  In Qt 2.0 QList is only implemented as a template class. Define a
  template instance QList\<X\> to create a list that operates on pointers
  to X, or X*.

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

    class Employee
    {
    public:
        Employee( const QString& name, int salary ) { n=name; s=salary; }
        QString     name()   const		 { return n; }
        int	    salary() const		 { return s; }
    private:
        QString     n;
        int         s;
    };

    void main()
    {
	QList<Employee> list;		// list of pointers to Employee
	list.setAutoDelete( TRUE );	// delete items when they are removed

	list.append( new Employee("Bill", 50000) );
	list.append( new Employee("Steve",80000) );
	list.append( new Employee("Ron",  60000) );

	Employee *emp;
	for ( emp=list.first(); emp != 0; emp=list.next() )
	    printf( "%s earns %d\n", emp->name().latin1(), emp->salary() );
    }
  \endcode

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

  The list class is indexable and has a \link at() current index\endlink
  and a \link current() current item\endlink.  The first item corresponds
  to index 0.  The current index is -1 if the current item is null.

  QList has several member functions for traversing the list, but using
  a QListIterator can be more practical. Multiple list iterators may
  traverse the same list, independent of each other and independent of
  the current list item.

  In the example above, we make the call setAutoDelete(TRUE).
  Enabling auto-deletion tells the list to delete items that are removed
  from the list.  The default is to not delete items when they are
  removed, but that would cause a memory leak in our example since we have
  no other references to the list items.

  List items are stored as \c void* in an internal QLNode, which also
  holds pointers to the next and previous list items.  The functions
  currentNode(), removeNode() and takeNode() operate directly on the
  QLNode, but they should be used with care.

  When inserting an item into a list, only the pointer is copied, not the
  item itself. This is called a shallow copy. It is possible to make the
  list copy all of the item's data (known as a deep copy) when an item is
  inserted.  insert(), inSort() and append() call the virtual function
  QCollection::newItem() for the item to be inserted.
  Inherit a list and reimplement it if you want deep copies.

  When removing an item from a list, the virtual function
  QCollection::deleteItem() is called.  QList's default implementation
  is to delete the item if auto-deletion is enabled.

  The virtual function QGList::compareItems() can be reimplemented to
  compare two list items. This function is called from all list functions
  that need to compare list items, for instance remove(const type*).
  If you only want to deal with pointers, there are functions that
  compare pointers instead, for instance removeRef(const type*).
  These functions are somewhat faster than those that call compareItems().

  The QStrList class in qstrlist.h is a list of \c char*.  QStrList is
  a good example of a list that reimplements newItem(), deleteItem() and
  compareItems()

  \sa QListIterator, \link collection.html Collection Classes\endlink
*/


/*!
  \fn QList::QList()
  Constructs an empty list.
*/

/*!
  \fn QList::QList( const QList<type> &list )
  Constructs a copy of \e list.

  Each item in \e list is \link append() appended\endlink to this list.
  Only the pointers are copied (shallow copy).
*/

/*!
  \fn QList::~QList()
  Removes all items from the list and destroys the list.

  All list iterators that access this list will be reset.

  \sa setAutoDelete()
*/

/*!
  \fn QList<type> &QList::operator=(const QList<type> &list)
  Assigns \e list to this list and returns a reference to this list.

  This list is first cleared, then each item in \e list is
  \link append() appended\endlink to this list.  Only the pointers are copied
  (shallow copy), unless newItem() has been reimplemented().
*/

/*!
  \fn bool QList::operator==(const QList<type> &list ) const

  Compares this list with \a list. Retruns TRUE if the lists
  contain the same data, else FALSE.
*/

/*!
  \fn uint QList::count() const
  Returns the number of items in the list.
  \sa isEmpty()
*/

/*!
  \fn void QList::sort()

  Sorts the list by the result of the virtual compareItems() function.

  The Heap-Sort algorithm is used for sorting.  It sorts n items with
  O(n*log n) compares.  This is the asymptotic optimal solution of the
  sorting problem.

  If the items in your list support operator< and operator== then you
  might be better off with QSortedList since it implements the
  compareItems() function for you using these two operators.

  \sa inSort()
*/

/*!
  \fn bool QList::isEmpty() const
  Returns TRUE if the list is empty, i.e. count() == 0. Returns FALSE
   otherwise.
  \sa count()
*/

/*!
  \fn bool QList::insert( uint index, const type *item )
  Inserts the \e item at the position \e index in the list.

  Returns TRUE if successful, or FALSE if \e index is out of range.
  The valid range is <code>0 .. count()</code> inclusive.
  The item is appended if \e index == count().

  The inserted item becomes the current list item.

  The \e item must not be a null pointer.

  \sa append(), current()
*/

/*!
  \fn void QList::inSort( const type *item )
  Inserts the \e item at its sorted position in the list.

  The sort order depends on the virtual QGList::compareItems() function.
  All items must be inserted with inSort() to maintain the sorting order.

  The inserted item becomes the current list item.

  The \e item must not be a null pointer.

  Please note that inSort is slow. If you want to insert lots of items
  in a list and sort after inserting then you should use sort().
  inSort() takes up to O(n) compares. That means inserting n items in
  your list will need O(n^2) compares while sort() only needs O(n*logn)
  for the same task. So you inSort() only if you already have a pre-sorted
  list and want to insert only few additional items.

  \sa insert(), QGList::compareItems(), current(), sort()
*/

/*!
  \fn void QList::append( const type *item )
  Inserts the \e item at the end of the list.

  The inserted item becomes the current list item.
  This is equivalent to \c insert(count(),item).


  The \e item must not be a null pointer.

  \sa insert(), current(), prepend()
*/

/*!
  \fn void QList::prepend( const type *item )

  Inserts the \e item at the start of the list.

  The inserted item becomes the current list item.
  This is equivalent to \c insert(0,item).

  The \e item must not be a null pointer.

  \sa append(), insert(), current()
*/

/*!
  \fn bool QList::remove( uint index )
  Removes the item at position \e index in the list.

  Returns TRUE if successful, or FALSE if \e index is out of range.
  The valid range is <code>0 .. (count() - 1)</code> inclusive.

  The removed item is deleted if \link QCollection::setAutoDelete()
  auto-deletion\endlink is enabled.

  The item after the removed item becomes the new current list item if
  the removed item is not the last item in the list.  If the last item
  is removed, the new last item becomes the current item in Qt 2.x.
  In 3.0, the current item will be set to null.  The current item is
  set to null if the list becomes empty.

  All list iterators that refer to the removed item will be set to point
  to the new current item.

  \sa take(), clear(), setAutoDelete(), current() removeRef()
*/

/*!
  \fn bool QList::remove()
  Removes the current list item.

  Returns TRUE if successful, or FALSE if the current item is null.

  The removed item is deleted if \link QCollection::setAutoDelete()
  auto-deletion\endlink is enabled.

  The item after the removed item becomes the new current list item if
  the removed item is not the last item in the list.  If the last item
  is removed, the new last item becomes the current item in Qt 2.x.
  In 3.0, the current item will be set to null.  The current item is
  set to null if the list becomes empty.

  All list iterators that refer to the removed item will be set to point
  to the new current item.

  \sa take(), clear(), setAutoDelete(), current() removeRef()
*/

/*!
  \fn bool QList::remove( const type *item )
  Removes the first occurrence of \e item from the list.

  Returns TRUE if successful, or FALSE if the item could not be found in the
  list.

  The removed item is deleted if \link QCollection::setAutoDelete()
  auto-deletion\endlink is enabled.

  The compareItems() function is called when searching for the item
  in the list. If compareItems() is not reimplemented, it is more
  efficient to call removeRef().

  The item after the removed item becomes the new current list item if
  the removed item is not the last item in the list.  If the last item
  is removed, the new last item becomes the current item in Qt 2.x.
  In 3.0, the current item will be set to null.  The current item is
  set to null if the list becomes empty.

  All list iterators that refer to the removed item will be set to point
  to the new current item.

  \sa removeRef(), take(), clear(), setAutoDelete(), compareItems(), current()
*/

/*!
  \fn bool QList::removeRef( const type *item )
  Removes the first occurrence of \e item from the list.

  Returns TRUE if successful, or FALSE if the item cannot be found in the
  list.

  The removed item is deleted if \link QCollection::setAutoDelete()
  auto-deletion\endlink is enabled.

  The list is scanned until the pointer \e item is found.  It is removed
  if it is found.

  Equivalent to:
  \code
    if ( list.findRef(item) != -1 )