qvarlengtharray.qdoc

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// Copyright (C) 2016 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GFDL-1.3-no-invariants-only
 
/*!
    \class QVarLengthArray
    \inmodule QtCore
    \brief The QVarLengthArray class provides a low-level variable-length array.
 
    \ingroup tools
    \reentrant
 
    The C++ language doesn't support variable-length arrays on the stack.
    For example, the following code won't compile:
 
    \snippet code/doc_src_qvarlengtharray.cpp 0
 
    The alternative is to allocate the array on the heap (with
    \c{new}):
 
    \snippet code/doc_src_qvarlengtharray.cpp 1
 
    However, if myfunc() is called very frequently from the
    application's inner loop, heap allocation can be a major source
    of slowdown.
 
    QVarLengthArray is an attempt to work around this gap in the C++
    language. It allocates a certain number of elements on the stack,
    and if you resize the array to a larger size, it automatically
    uses the heap instead. Stack allocation has the advantage that
    it is much faster than heap allocation.
 
    Example:
    \snippet code/doc_src_qvarlengtharray.cpp 2
 
    In the example above, QVarLengthArray will preallocate 1024
    elements on the stack and use them unless \c{n + 1} is greater
    than 1024. If you omit the second template argument,
    QVarLengthArray's default of 256 is used.
 
    QVarLengthArray's value type must be an \l{assignable data type}.
    This covers most data types that are commonly used, but the
    compiler won't let you, for example, store a QWidget as a value;
    instead, store a QWidget *.
 
    QVarLengthArray, like QList, provides a resizable array data
    structure. The main differences between the two classes are:
 
    \list
    \li QVarLengthArray's API is much more low-level and it lacks
        some of QList's functionality.
 
    \li QVarLengthArray doesn't initialize the memory if the value is
        a basic type. (QList always does.)
 
    \li QList uses \l{implicit sharing} as a memory optimization.
        QVarLengthArray doesn't provide that feature; however, it
        usually produces slightly better performance due to reduced
        overhead, especially in tight loops.
    \endlist
 
    In summary, QVarLengthArray is a low-level optimization class
    that only makes sense in very specific cases. It is used a few
    places inside Qt and was added to Qt's public API for the
    convenience of advanced users.
 
    \sa QList
*/
 
/*! \fn template<class T, qsizetype Prealloc> QVarLengthArray<T, Prealloc>::QVarLengthArray()
 
    Constructs an array with an initial size of zero.
*/
 
/*! \fn template<class T, qsizetype Prealloc> QVarLengthArray<T, Prealloc>::QVarLengthArray(qsizetype size)
 
    Constructs an array with an initial size of \a size elements.
 
    If the value type is a primitive type (e.g., char, int, float) or
    a pointer type (e.g., QWidget *), the elements are not
    initialized. For other types, the elements are initialized with a
    \l{default-constructed value}.
*/
 
/*!
    \fn template<class T, qsizetype Prealloc> QVarLengthArray<T, Prealloc>::QVarLengthArray(qsizetype size, const T &v)
    \since 6.4
 
    Constructs an array with an initial size of \a size elements filled with
    copies of \a v.
 
    \note This constructor is only available when \c T is copy-constructible.
 
    \sa size(), squeeze()
*/
 
 
/*! \fn template<class T, qsizetype Prealloc> QVarLengthArray<T, Prealloc>::QVarLengthArray(std::initializer_list<T> args)
    \since 5.5
 
    Constructs an array from the std::initializer_list given by \a args.
*/
 
/*! \fn template<class T, qsizetype Prealloc> template<typename InputIterator, QVarLengthArray<T, Prealloc>::if_input_iterator<InputIterator>> QVarLengthArray<T, Prealloc>::QVarLengthArray(InputIterator first, InputIterator last)
    \since 5.14
 
    Constructs an array with the contents in the iterator range [\a first, \a last).
 
    This constructor only participates in overload resolution if
    \c InputIterator meets the requirements of an
    \l {https://en.cppreference.com/w/cpp/named_req/InputIterator} {LegacyInputIterator}.
 
    The value type of \c InputIterator must be convertible to \c T.
*/
 
 
/*! \fn template<class T, qsizetype Prealloc> QVarLengthArray<T, Prealloc>::~QVarLengthArray()
 
    Destroys the array.
*/
 
/*! \fn template<class T, qsizetype Prealloc> qsizetype QVarLengthArray<T, Prealloc>::size() const
 
    Returns the number of elements in the array.
 
    \sa isEmpty(), resize()
*/
 
/*! \fn template<class T, qsizetype Prealloc> qsizetype QVarLengthArray<T, Prealloc>::count() const
 
    Same as size().
 
    \sa isEmpty(), resize()
*/
 
/*! \fn template<class T, qsizetype Prealloc> qsizetype QVarLengthArray<T, Prealloc>::length() const
    \since 5.0
 
    Same as size().
 
    \sa isEmpty(), resize()
*/
 
/*! \fn template<class T, qsizetype Prealloc> qsizetype QVarLengthArray<T, Prealloc>::max_size()
    \since 6.8
 
    This function is provided for STL compatibility.
    It returns the maximum number of elements that the array can
    theoretically hold. In practice, the number can be much smaller,
    limited by the amount of memory available to the system.
*/
 
/*! \fn template<class T, qsizetype Prealloc> T& QVarLengthArray<T, Prealloc>::first()
 
    Returns a reference to the first item in the array. The array must
    not be empty. If the array can be empty, check isEmpty() before
    calling this function.
 
    \sa last(), isEmpty()
*/
 
/*! \fn template<class T, qsizetype Prealloc> const T& QVarLengthArray<T, Prealloc>::first() const
 
    \overload
*/
 
/*! \fn template<class T, qsizetype Prealloc> T& QVarLengthArray<T, Prealloc>::front()
    \since 5.0
 
    Same as first(). Provided for STL-compatibility.
*/
 
/*! \fn template<class T, qsizetype Prealloc> const T& QVarLengthArray<T, Prealloc>::front() const
    \since 5.0
 
    \overload
*/
 
/*! \fn template<class T, qsizetype Prealloc> T& QVarLengthArray<T, Prealloc>::last()
 
    Returns a reference to the last item in the array.  The array must
    not be empty. If the array can be empty, check isEmpty() before
    calling this function.
 
    \sa first(), isEmpty()
*/
 
/*! \fn template<class T, qsizetype Prealloc> const T& QVarLengthArray<T, Prealloc>::last() const
 
    \overload
*/
 
/*! \fn template<class T, qsizetype Prealloc> T& QVarLengthArray<T, Prealloc>::back()
    \since 5.0
 
    Same as last(). Provided for STL-compatibility.
*/
 
/*! \fn template<class T, qsizetype Prealloc> const T& QVarLengthArray<T, Prealloc>::back() const
    \since 5.0
 
    \overload
*/
 
/*! \fn template<class T, qsizetype Prealloc> void QVarLengthArray<T, Prealloc>::shrink_to_fit()
    \since 5.10
 
    Same as squeeze(). Provided for STL-compatibility.
*/
 
/*! \fn template<class T, qsizetype Prealloc> bool QVarLengthArray<T, Prealloc>::isEmpty() const
 
    Returns \c true if the array has size 0; otherwise returns \c false.
 
    \sa size(), resize()
*/
 
/*! \fn template<class T, qsizetype Prealloc> bool QVarLengthArray<T, Prealloc>::empty() const
    \since 5.0
 
    Returns \c true if the array has size 0; otherwise returns \c false.
 
    Same as isEmpty(). Provided for STL-compatibility.
*/
 
/*! \fn template<class T, qsizetype Prealloc> void QVarLengthArray<T, Prealloc>::clear()
 
    Removes all the elements from the array.
 
    Same as resize(0).
*/
 
/*! \fn template<class T, qsizetype Prealloc> void QVarLengthArray<T, Prealloc>::resize(qsizetype size)
 
    Sets the size of the array to \a size. If \a size is greater than
    the current size, elements are added to the end. If \a size is
    less than the current size, elements are removed from the end.
 
    If the value type is a primitive type (e.g., char, int, float) or
    a pointer type (e.g., QWidget *), new elements are not
    initialized. For other types, the elements are initialized with a
    \l{default-constructed value}.
 
    \sa size(), squeeze()
*/
 
/*!
    \fn template<class T, qsizetype Prealloc> void QVarLengthArray<T, Prealloc>::resize(qsizetype size, const T &v)
    \since 6.4
 
    Sets the size of the array to \a size. If \a size is greater than
    the current size, copies of \a v are added to the end. If \a size is
    less than the current size, elements are removed from the end.
 
    \note This function is only available when \c T is copy-constructible.
 
    \sa size(), squeeze()
*/
 
/*! \fn template<class T, qsizetype Prealloc> qsizetype QVarLengthArray<T, Prealloc>::capacity() const
 
    Returns the maximum number of elements that can be stored in the
    array without forcing a reallocation.
 
    The sole purpose of this function is to provide a means of fine
    tuning QVarLengthArray's memory usage. In general, you will rarely ever
    need to call this function. If you want to know how many items are
    in the array, call size().
 
    \sa reserve(), squeeze()
*/
 
/*! \fn template<class T, qsizetype Prealloc> void QVarLengthArray<T, Prealloc>::reserve(qsizetype size)
 
    Attempts to allocate memory for at least \a size elements. If you
    know in advance how large the array can get, you can call this
    function and if you call resize() often, you are likely to get
    better performance. If \a size is an underestimate, the worst
    that will happen is that the QVarLengthArray will be a bit
    slower.
 
    The sole purpose of this function is to provide a means of fine
    tuning QVarLengthArray's memory usage. In general, you will
    rarely ever need to call this function. If you want to change the
    size of the array, call resize().
 
    \sa capacity(), squeeze()
*/
 
/*! \fn template<class T, qsizetype Prealloc> void QVarLengthArray<T, Prealloc>::squeeze()
    \since 5.1
 
    Releases any memory not required to store the items.
    If the container can fit its storage on the stack allocation,
    it will free the heap allocation and copy the elements back to the stack.
 
    The sole purpose of this function is to provide a means of fine
    tuning QVarLengthArray's memory usage. In general, you will rarely ever
    need to call this function.
 
    \sa reserve(), capacity(), resize()
*/
 
/*! \fn template<class T, qsizetype Prealloc> T &QVarLengthArray<T, Prealloc>::operator[](qsizetype i)
 
    Returns a reference to the item at index position \a i.
 
    \a i must be a valid index position in the array (i.e., 0 <= \a i
    < size()).
 
    \sa data(), at()
*/
 
/*! \fn template<class T, qsizetype Prealloc> const T &QVarLengthArray<T, Prealloc>::operator[](qsizetype i) const
 
    \overload
*/
 
 
/*!
    \fn template<class T, qsizetype Prealloc> void QVarLengthArray<T, Prealloc>::append(const T &t)
 
    Appends item \a t to the array, extending the array if necessary.
 
    \sa removeLast()
*/
 
/*!
    \fn template<class T, qsizetype Prealloc> void QVarLengthArray<T, Prealloc>::push_back(const T &t)
    \since 5.0
 
    Appends item \a t to the array, extending the array if necessary.
    Provided for STL-compatibility.
*/
 
/*!
    \fn template<class T, qsizetype Prealloc> void QVarLengthArray<T, Prealloc>::append(T &&t)
    \overload append
    \since 5.9
 
    \note Unlike the lvalue overload of append(), passing a reference to
    an object that is already an element of \c *this leads to undefined
    behavior:
 
    \code
    vla.append(std::move(vla[0])); // BUG: passing an object that is already in the container
    \endcode
*/
 
/*!
    \fn template<class T, qsizetype Prealloc> void QVarLengthArray<T, Prealloc>::push_back(T &&t)
    \overload push_back
    \since 5.9
 
    \note Unlike the lvalue overload of push_back(), passing a reference to
    an object that is already an element of \c *this leads to undefined
    behavior:
 
    \code
    vla.push_back(std::move(vla[0])); // BUG: passing an object that is already in the container
    \endcode
*/
 
/*!
    \fn template<class T, qsizetype Prealloc> inline void QVarLengthArray<T, Prealloc>::removeLast()
    \since 4.5
 
    Decreases the size of the array by one.  The allocated size is not changed.
 
    \sa append()
*/
 
/*!
    \fn template<class T, qsizetype Prealloc> void QVarLengthArray<T, Prealloc>::pop_back()
    \since 5.0
 
    Same as removeLast(). Provided for STL-compatibility.
*/
 
/*!
    \fn template<class T, qsizetype Prealloc> void QVarLengthArray<T, Prealloc>::append(const T *buf, qsizetype size)
 
    Appends \a size amount of items referenced by \a buf to this array.
*/
 
 
/*! \fn template<class T, qsizetype Prealloc> T *QVarLengthArray<T, Prealloc>::data()
 
    Returns a pointer to the data stored in the array. The pointer can
    be used to access and modify the items in the array.
 
    Example:
    \snippet code/doc_src_qvarlengtharray.cpp 3
 
    The pointer remains valid as long as the array isn't reallocated.
 
    This function is mostly useful to pass an array to a function
    that accepts a plain C++ array.
 
    \sa constData(), operator[]()
*/
 
/*! \fn template<class T, qsizetype Prealloc> const T *QVarLengthArray<T, Prealloc>::data() const
 
    \overload
*/
 
/*! \fn template<class T, qsizetype Prealloc> const T *QVarLengthArray<T, Prealloc>::constData() const
 
    Returns a const pointer to the data stored in the array. The
    pointer can be used to access the items in the array. The
    pointer remains valid as long as the array isn't reallocated.
 
    This function is mostly useful to pass an array to a function
    that accepts a plain C++ array.
 
    \sa data(), operator[]()
*/
 
/*! \fn template<class T, qsizetype Prealloc> QVarLengthArray<T, Prealloc> &QVarLengthArray<T, Prealloc>::operator=(const QVarLengthArray<T, Prealloc> &other)
    Assigns \a other to this array and returns a reference to this array.
 */
 
/*! \fn template<class T, qsizetype Prealloc> QVarLengthArray<T, Prealloc> &QVarLengthArray<T, Prealloc>::operator=(QVarLengthArray<T, Prealloc> &&other)
    Move-assigns \a other to this array and returns a reference to this array.
    After the move, \a other is empty.
    \since 6.0
 */
 
/*! \fn template<class T, qsizetype Prealloc> QVarLengthArray<T, Prealloc> &QVarLengthArray<T, Prealloc>::operator=(std::initializer_list<T> list)
    \since 5.5
 
    Assigns the values of \a list to this array, and returns a reference to this array.
*/
 
/*! \fn template<class T, qsizetype Prealloc> QVarLengthArray<T, Prealloc>::QVarLengthArray(const QVarLengthArray<T, Prealloc> &other)
    Constructs a copy of \a other.
 */
 
/*! \fn template<class T, qsizetype Prealloc> QVarLengthArray<T, Prealloc>::QVarLengthArray(QVarLengthArray<T, Prealloc> &&other)
    Move-constructs this variable-length array from \a other. After the move, \a other is empty.
    \since 6.0
 */
 
/*! \fn template<class T, qsizetype Prealloc> const T &QVarLengthArray<T, Prealloc>::at(qsizetype i) const
 
    Returns a reference to the item at index position \a i.
 
    \a i must be a valid index position in the array (i.e., 0 <= \a i
    < size()).
 
    \sa value(), operator[]()
*/
 
/*! \fn template<class T, qsizetype Prealloc> T QVarLengthArray<T, Prealloc>::value(qsizetype i) const
 
    Returns the value at index position \a i.
 
    If the index \a i is out of bounds, the function returns
    a \l{default-constructed value}. If you are certain that
    \a i is within bounds, you can use at() instead, which is slightly
    faster.
 
    \sa at(), operator[]()
*/
 
/*! \fn template<class T, qsizetype Prealloc> T QVarLengthArray<T, Prealloc>::value(qsizetype i, const T &defaultValue) const
 
    \overload
 
    If the index \a i is out of bounds, the function returns
    \a defaultValue.
*/
 
/*
    \var QVarLengthArray::PreallocatedSize
    \since 6.8
 
    The same value as the \c{Prealloc} template argument. Provided for easier
    access compared to manually extracting the value from the template
    argument.
*/
 
/*!
    \typedef QVarLengthArray::size_type
    \since 4.7
 
    Typedef for int. Provided for STL compatibility.
*/
 
/*!
    \typedef QVarLengthArray::value_type
    \since 4.7
 
    Typedef for T. Provided for STL compatibility.
*/
 
/*!
    \typedef QVarLengthArray::difference_type
    \since 4.7
 
    Typedef for ptrdiff_t. Provided for STL compatibility.
*/
 
/*!
    \typedef QVarLengthArray::pointer
    \since 4.7
 
    Typedef for T *. Provided for STL compatibility.
*/
 
/*!
    \typedef QVarLengthArray::const_pointer
    \since 4.7
 
    Typedef for const T *. Provided for STL compatibility.
*/
 
/*!
    \typedef QVarLengthArray::reference
    \since 4.7
 
    Typedef for T &. Provided for STL compatibility.
*/
 
/*!
    \typedef QVarLengthArray::const_reference
    \since 4.7
 
    Typedef for const T &. Provided for STL compatibility.
*/
 
/*!
    \typedef QVarLengthArray::const_iterator
    \since 4.7
 
    Typedef for const T *. Provided for STL compatibility.
*/
 
/*!
    \typedef QVarLengthArray::iterator
    \since 4.7
 
    Typedef for T *. Provided for STL compatibility.
*/
 
/*!
    \typedef QVarLengthArray::const_reverse_iterator
    \since 5.6
 
    Typedef for \c{std::reverse_iterator<const T*>}. Provided for STL compatibility.
*/
 
/*!
    \typedef QVarLengthArray::reverse_iterator
    \since 5.6
 
    Typedef for \c{std::reverse_iterator<T*>}. Provided for STL compatibility.
*/
 
/*!
    \fn template<class T, qsizetype Prealloc> void QVarLengthArray<T, Prealloc>::prepend(const T &value)
    \fn template<class T, qsizetype Prealloc> void QVarLengthArray<T, Prealloc>::prepend(T &&value)
 
    \since 4.8
    \deprecated [6.3] This is slow. If you must, use \c{insert(cbegin(), ~~~)} instead.
 
    Inserts \a value at the beginning of the array.
 
 
    This is the same as vector.insert(0, \a value).
 
    For large arrays, this operation can be slow (\l{linear time}),
    because it requires moving all the items in the vector by one
    position further in memory. If you want a container class that
    provides a fast prepend() function, use std::list instead.
 
    \sa append(), insert()
*/
 
/*! \fn template<class T, qsizetype Prealloc> void QVarLengthArray<T, Prealloc>::replace(qsizetype i, const T &value)
 
    \since 4.8
    Replaces the item at index position \a i with \a value.
 
    \a i must be a valid index position in the array (i.e., 0 <= \a
    i < size()).
 
    \sa operator[](), remove()
*/
 
/*! \fn template<class T, qsizetype Prealloc> void QVarLengthArray<T, Prealloc>::remove(qsizetype i, qsizetype count)
 
    \overload
    \since 4.8
 
    Removes \a count elements from the middle of the array, starting at
    index position \a i.
 
    \sa insert(), replace()
*/
 
/*! \fn template<class T, qsizetype Prealloc> QVarLengthArray<T, Prealloc>::iterator QVarLengthArray<T, Prealloc>::begin()
    \since 4.8
 
    Returns an \l{STL-style iterators}{STL-style iterator} pointing to the first item in
    the array.
 
    \sa constBegin(), end()
*/
 
/*! \fn template<class T, qsizetype Prealloc> QVarLengthArray<T, Prealloc>::const_iterator QVarLengthArray<T, Prealloc>::begin() const
    \since 4.8
    \overload
*/
 
/*! \fn template<class T, qsizetype Prealloc> QVarLengthArray<T, Prealloc>::const_iterator QVarLengthArray<T, Prealloc>::cbegin() const
    \since 5.0
 
    Returns a const \l{STL-style iterators}{STL-style iterator} pointing to the first item
    in the array.
 
    \sa begin(), cend()
*/
 
/*! \fn template<class T, qsizetype Prealloc> QVarLengthArray<T, Prealloc>::const_iterator QVarLengthArray<T, Prealloc>::constBegin() const
    \since 4.8
 
    Returns a const \l{STL-style iterators}{STL-style iterator} pointing to the first item
    in the array.
 
    \sa begin(), constEnd()
*/
 
/*! \fn template<class T, qsizetype Prealloc> QVarLengthArray<T, Prealloc>::iterator QVarLengthArray<T, Prealloc>::end()
    \since 4.8
 
    Returns an \l{STL-style iterators}{STL-style iterator} pointing to the imaginary item
    after the last item in the array.
 
    \sa begin(), constEnd()
*/
 
/*! \fn template<class T, qsizetype Prealloc> QVarLengthArray<T, Prealloc>::const_iterator QVarLengthArray<T, Prealloc>::end() const
    \since 4.8
 
    \overload
*/
 
/*! \fn template<class T, qsizetype Prealloc> QVarLengthArray<T, Prealloc>::const_iterator QVarLengthArray<T, Prealloc>::cend() const
    \since 5.0
 
    Returns a const \l{STL-style iterators}{STL-style iterator} pointing to the imaginary
    item after the last item in the array.
 
    \sa cbegin(), end()
*/
 
/*! \fn template<class T, qsizetype Prealloc> QVarLengthArray<T, Prealloc>::const_iterator QVarLengthArray<T, Prealloc>::constEnd() const
    \since 4.8
 
    Returns a const \l{STL-style iterators}{STL-style iterator} pointing to the imaginary
    item after the last item in the array.
 
    \sa constBegin(), end()
*/
 
/*! \fn template<class T, qsizetype Prealloc> QVarLengthArray<T, Prealloc>::reverse_iterator QVarLengthArray<T, Prealloc>::rbegin()
    \since 5.6
 
    Returns a \l{STL-style iterators}{STL-style} reverse iterator pointing to the first
    item in the variable length array, in reverse order.
 
    \sa begin(), crbegin(), rend()
*/
 
/*! \fn template<class T, qsizetype Prealloc> QVarLengthArray<T, Prealloc>::const_reverse_iterator QVarLengthArray<T, Prealloc>::rbegin() const
    \since 5.6
    \overload
*/
 
/*! \fn template<class T, qsizetype Prealloc> QVarLengthArray<T, Prealloc>::const_reverse_iterator QVarLengthArray<T, Prealloc>::crbegin() const
    \since 5.6
 
    Returns a const \l{STL-style iterators}{STL-style} reverse iterator pointing to the first
    item in the variable length array, in reverse order.
 
    \sa begin(), rbegin(), rend()
*/
 
/*! \fn template<class T, qsizetype Prealloc> QVarLengthArray<T, Prealloc>::reverse_iterator QVarLengthArray<T, Prealloc>::rend()
    \since 5.6
 
    Returns a \l{STL-style iterators}{STL-style} reverse iterator pointing to one past
    the last item in the variable length array, in reverse order.
 
    \sa end(), crend(), rbegin()
*/
 
/*! \fn template<class T, qsizetype Prealloc> QVarLengthArray<T, Prealloc>::const_reverse_iterator QVarLengthArray<T, Prealloc>::rend() const
    \since 5.6
    \overload
*/
 
/*! \fn template<class T, qsizetype Prealloc> QVarLengthArray<T, Prealloc>::const_reverse_iterator QVarLengthArray<T, Prealloc>::crend() const
    \since 5.6
 
    Returns a const \l{STL-style iterators}{STL-style} reverse iterator pointing to one
    past the last item in the variable length array, in reverse order.
 
    \sa end(), rend(), rbegin()
*/
 
/*! \fn template<class T, qsizetype Prealloc> QVarLengthArray<T, Prealloc>::iterator QVarLengthArray<T, Prealloc>::erase(const_iterator pos)
    \since 4.8
 
    Removes the item pointed to by the iterator \a pos from the
    vector, and returns an iterator to the next item in the vector
    (which may be end()).
 
    \sa insert(), remove()
*/
 
/*! \fn template<class T, qsizetype Prealloc> QVarLengthArray<T, Prealloc>::iterator QVarLengthArray<T, Prealloc>::erase(const_iterator begin, const_iterator end)
 
    \overload
    \since 4.8
 
    Removes all the items from \a begin up to (but not including) \a
    end. Returns an iterator to the same item that \a end referred to
    before the call.
*/
 
/*!
    \fn template<class T, qsizetype Prealloc> void QVarLengthArray<T, Prealloc>::insert(qsizetype i, const T &value)
    \fn template<class T, qsizetype Prealloc> void QVarLengthArray<T, Prealloc>::insert(qsizetype i, T &&value)
    \since 4.8
 
    Inserts \a value at index position \a i in the array. If \a i is
    0, the value is prepended to the vector. If \a i is size(), the
    value is appended to the vector.
 
    For large arrays, this operation can be slow (\l{linear time}),
    because it requires moving all the items at indexes \a i and
    above by one position further in memory. If you want a container
    class that provides a fast insert() function, use std::list
    instead.
 
    \sa remove()
*/
 
/*! \fn template<class T, qsizetype Prealloc> void QVarLengthArray<T, Prealloc>::insert(qsizetype i, qsizetype count, const T &value)
 
    \overload
    \since 4.8
 
    Inserts \a count copies of \a value at index position \a i in the
    vector.
*/
 
/*! \fn template<class T, qsizetype Prealloc> QVarLengthArray<T, Prealloc>::iterator QVarLengthArray<T, Prealloc>::insert(const_iterator before, const T &value)
    \fn template<class T, qsizetype Prealloc> QVarLengthArray<T, Prealloc>::iterator QVarLengthArray<T, Prealloc>::insert(const_iterator before, T &&value)
 
    \overload
    \since 4.8
 
    Inserts \a value in front of the item pointed to by the iterator
    \a before. Returns an iterator pointing at the inserted item.
*/
 
/*!
    \fn template <class T, qsizetype Prealloc> template <typename...Args> QVarLengthArray<T, Prealloc>::iterator QVarLengthArray<T, Prealloc>::emplace(const_iterator pos, Args &&...args)
 
    \since 6.3
 
    Inserts an item in front of the item pointed to by the iterator
    \a pos, passing \a args to its constructor.
 
    Returns an iterator pointing at the emplaced item.
*/
 
/*!
    \fn template <class T, qsizetype Prealloc> template <typename...Args> T &QVarLengthArray<T, Prealloc>::emplace_back(Args &&...args)
    \since 6.3
 
    Inserts an item at the back of this QVarLengthArray, passing
    \a args to its constructor.
 
    Returns a reference to the emplaced item.
*/
 
/*! \fn template<class T, qsizetype Prealloc> QVarLengthArray<T, Prealloc>::iterator QVarLengthArray<T, Prealloc>::insert(const_iterator before, qsizetype count, const T &value)
 
    \since 4.8
    Inserts \a count copies of \a value in front of the item pointed to
    by the iterator \a before. Returns an iterator pointing at the
    first of the inserted items.
*/
 
 
 
/*! \fn template<class T, qsizetype Prealloc1, qsizetype Prealloc2> bool operator==(const QVarLengthArray<T, Prealloc1> &left, const QVarLengthArray<T, Prealloc2> &right)
 
    \relates QVarLengthArray
    \since 4.8
    Returns \c true if the two arrays, specified by \a left and \a right, are equal.
 
    Two arrays are considered equal if they contain the same values
    in the same order.
 
    This function requires the value type to have an implementation
    of \c operator==().
 
    \sa {operator!=(const QVarLengthArray<T, Prealloc1> &left, const QVarLengthArray<T, Prealloc2> &right)}{operator!=()}
*/
 
/*! \fn template<typename T, qsizetype Prealloc1, qsizetype Prealloc2> bool operator!=(const QVarLengthArray<T, Prealloc1> &left, const QVarLengthArray<T, Prealloc2> &right)
 
    \relates QVarLengthArray
    \since 4.8
    Returns \c true if the two arrays, specified by \a left and \a right, are \e not equal.
 
    Two arrays are considered equal if they contain the same values
    in the same order.
 
    This function requires the value type to have an implementation
    of \c operator==().
 
    \sa {operator==(const QVarLengthArray<T, Prealloc1> &left, const QVarLengthArray<T, Prealloc2> &right)}{operator==()}
*/
 
/*! \fn template<typename T, qsizetype Prealloc1, qsizetype Prealloc2> bool operator<(const QVarLengthArray<T,Prealloc1> &lhs, const QVarLengthArray<T,Prealloc2> &rhs)
    \since 5.6
    \relates QVarLengthArray
 
    Returns \c true if variable length array \a lhs is
    \l{http://en.cppreference.com/w/cpp/algorithm/lexicographical_compare}
    {lexicographically less than} \a rhs; otherwise returns \c false.
 
    This function requires the value type to have an implementation
    of \c operator<().
*/
 
/*! \fn template<typename T, qsizetype Prealloc1, qsizetype Prealloc2> bool operator<=(const QVarLengthArray<T,Prealloc1> &lhs, const QVarLengthArray<T,Prealloc2> &rhs)
    \since 5.6
    \relates QVarLengthArray
 
    Returns \c true if variable length array \a lhs is
    \l{http://en.cppreference.com/w/cpp/algorithm/lexicographical_compare}
    {lexicographically less than or equal to} \a rhs; otherwise returns \c false.
 
    This function requires the value type to have an implementation
    of \c operator<().
*/
 
/*! \fn template<typename T, qsizetype Prealloc1, qsizetype Prealloc2> bool operator>(const QVarLengthArray<T,Prealloc1> &lhs, const QVarLengthArray<T,Prealloc2> &rhs)
    \since 5.6
    \relates QVarLengthArray
 
    Returns \c true if variable length array \a lhs is
    \l{http://en.cppreference.com/w/cpp/algorithm/lexicographical_compare}
    {lexicographically greater than} \a rhs; otherwise returns \c false.
 
    This function requires the value type to have an implementation
    of \c operator<().
*/
 
/*! \fn template<typename T, qsizetype Prealloc1, qsizetype Prealloc2> bool operator>=(const QVarLengthArray<T,Prealloc1> &lhs, const QVarLengthArray<T,Prealloc2> &rhs)
    \since 5.6
    \relates QVarLengthArray
 
    Returns \c true if variable length array \a lhs is
    \l{http://en.cppreference.com/w/cpp/algorithm/lexicographical_compare}
    {lexicographically greater than or equal to} \a rhs; otherwise returns \c false.
 
    This function requires the value type to have an implementation
    of \c operator<().
*/
 
/*! \fn template<class T, qsizetype Prealloc> QVarLengthArray<T, Prealloc> &QVarLengthArray<T, Prealloc>::operator<<(const T &value)
 
    \since 4.8
    Appends \a value to the array and returns a reference to this
    vector.
 
    \sa append(), operator+=()
*/
 
/*! \fn template<class T, qsizetype Prealloc> QVarLengthArray<T, Prealloc> &QVarLengthArray<T, Prealloc>::operator<<(T &&value)
    \since 5.11
 
    \overload
 
    \sa append(), operator+=()
*/
 
/*! \fn template<class T, qsizetype Prealloc> QVarLengthArray<T, Prealloc> &QVarLengthArray<T, Prealloc>::operator+=(const T &value)
 
    \since 4.8
    Appends \a value to the array and returns a reference to this vector.
 
    \sa append(), operator<<()
*/
 
/*! \fn template<class T, qsizetype Prealloc> QVarLengthArray<T, Prealloc> &QVarLengthArray<T, Prealloc>::operator+=(T &&value)
    \since 5.11
 
    \overload
 
    \sa append(), operator<<()
*/
 
/*! \fn template<class T, qsizetype Prealloc> template <typename AT = T> qsizetype QVarLengthArray<T, Prealloc>::indexOf(const AT &value, qsizetype from = 0) const
 
    \since 5.3
    Returns the index position of the first occurrence of \a value in
    the array, searching forward from index position \a from.
    Returns -1 if no item matched.
 
    This function requires the value type to have an implementation of
    \c operator==().
 
    \sa lastIndexOf(), contains()
*/
 
/*! \fn template<class T, qsizetype Prealloc> template <typename AT = T> qsizetype QVarLengthArray<T, Prealloc>::lastIndexOf(const AT &value, qsizetype from = -1) const
 
    \since 5.3
    Returns the index position of the last occurrence of the value \a
    value in the array, searching backward from index position \a
    from. If \a from is -1 (the default), the search starts at the
    last item. Returns -1 if no item matched.
 
    This function requires the value type to have an implementation of
    \c operator==().
 
    \sa indexOf(), contains()
*/
 
/*! \fn template<class T, qsizetype Prealloc> template <typename AT = T> bool QVarLengthArray<T, Prealloc>::contains(const AT &value) const
 
    \since 5.3
    Returns \c true if the array contains an occurrence of \a value;
    otherwise returns \c false.
 
    This function requires the value type to have an implementation of
    \c operator==().
 
    \sa indexOf(), lastIndexOf()
*/
 
/*!
    \fn template <typename T, qsizetype Prealloc> size_t qHash(const QVarLengthArray<T, Prealloc> &key, size_t seed = 0)
    \relates QVarLengthArray
    \since 5.14
 
    Returns the hash value for \a key, using \a seed to seed the
    calculation.
*/
 
/*! \fn template <typename T, qsizetype Prealloc> template <typename AT = T> qsizetype QVarLengthArray<T, Prealloc>::removeAll(const AT &t)
    \since 6.1
 
    Removes all elements that compare equal to \a t from the
    array. Returns the number of elements removed, if any.
 
    \sa removeOne()
*/
 
/*! \fn template <typename T, qsizetype Prealloc> template <typename AT = T> bool QVarLengthArray<T, Prealloc>::removeOne(const AT &t)
    \since 6.1
 
    Removes the first element that compares equal to \a t from the
    array. Returns whether an element was, in fact, removed.
 
    \sa removeAll()
*/
 
/*! \fn template <typename T, qsizetype Prealloc> template <typename Predicate> qsizetype QVarLengthArray<T, Prealloc>::removeIf(Predicate pred)
    \since 6.1
 
    Removes all elements for which the predicate \a pred returns true
    from the array. Returns the number of elements removed, if any.
 
    \sa removeAll()
*/
 
/*! \fn template <typename T, qsizetype Prealloc, typename AT> qsizetype erase(QVarLengthArray<T, Prealloc> &array, const AT &t)
    \relates QVarLengthArray
    \since 6.1
 
    Removes all elements that compare equal to \a t from the
    array \a array. Returns the number of elements removed, if any.
 
    \note \a t is not allowed to be a reference to an element inside \a
    array. If you cannot be sure that this is not the case, take a copy
    of \a t and call this function with the copy.
 
    \sa erase_if()
*/
 
/*! \fn template <typename T, qsizetype Prealloc, typename Predicate> qsizetype erase_if(QVarLengthArray<T, Prealloc> &array, Predicate pred)
    \relates QVarLengthArray
    \since 6.1
 
    Removes all elements for which the predicate \a pred returns true
    from the list \a array. Returns the number of elements removed, if
    any.
 
    \sa erase()
*/
 
/*! \fn template <class T, qsizetype Prealloc> QVarLengthArray<T, Prealloc>& QVarLengthArray<T, Prealloc>::assign(qsizetype n, const T &t)
    \since 6.6
 
    Replaces the contents of this container with \a n copies of \a t.
 
    The size of this container will be equal to \a n. This function will only
    allocate memory if \a n exceeds the capacity of the container.
*/
 
/*! \fn template <class T, qsizetype Prealloc> template <typename InputIterator, QVarLengthArray<T, Prealloc>::if_input_iterator<InputIterator>> QVarLengthArray<T, Prealloc>& QVarLengthArray<T, Prealloc>::assign(InputIterator first, InputIterator last)
    \since 6.6
 
    Replaces the contents of this container with a copy of the elements in the
    iterator range [\a first, \a last).
 
    The size of this container will be equal to the number of elements in the
    range [\a first, \a last). This function will only allocate memory if the
    number of elements in the range exceeds the capacity of the container.
 
    This function overload only participates in overload resolution if
    \c InputIterator meets the requirements of an
    \l {https://en.cppreference.com/w/cpp/named_req/InputIterator} {LegacyInputIterator}.
 
    The behavior is undefined if either argument is an iterator into *this.
*/
 
/*! \fn template <class T, qsizetype Prealloc> QVarLengthArray<T, Prealloc>& QVarLengthArray<T, Prealloc>::assign(std::initializer_list<T> list)
    \since 6.6
 
    Replaces the contents of this container with a copy of the elements of \a list.
 
    The size of this container will be equal to the number of elements in \a list.
 
    This function only allocates memory if the number of elements in \a list
    exceeds the capacity of the container.
*/