# Obsolete Members for <QtAlgorithms>

**The following members of class <QtAlgorithms> are obsolete.** They are provided to keep old source code working. We strongly advise against using them in new code.

## Functions

`(obsolete) ` RandomAccessIterator | qBinaryFind(RandomAccessIterator begin, RandomAccessIterator end, const T &value) |

`(obsolete) ` RandomAccessIterator | qBinaryFind(RandomAccessIterator begin, RandomAccessIterator end, const T &value, LessThan lessThan) |

`(obsolete) ` typename Container::const_iterator | qBinaryFind(const Container &container, const T &value) |

`(obsolete) ` OutputIterator | qCopy(InputIterator begin1, InputIterator end1, OutputIterator begin2) |

`(obsolete) ` BiIterator2 | qCopyBackward(BiIterator1 begin1, BiIterator1 end1, BiIterator2 end2) |

`(obsolete) ` void | qCount(InputIterator begin, InputIterator end, const T &value, Size &n) |

`(obsolete) ` void | qCount(const Container &container, const T &value, Size &n) |

`(obsolete) ` bool | qEqual(InputIterator1 begin1, InputIterator1 end1, InputIterator2 begin2) |

`(obsolete) ` void | qFill(ForwardIterator begin, ForwardIterator end, const T &value) |

`(obsolete) ` void | qFill(Container &container, const T &value) |

`(obsolete) ` InputIterator | qFind(InputIterator begin, InputIterator end, const T &value) |

`(obsolete) ` typename Container::const_iterator | qFind(const Container &container, const T &value) |

`(obsolete) ` LessThan | qGreater() |

`(obsolete) ` LessThan | qLess() |

`(obsolete) ` RandomAccessIterator | qLowerBound(RandomAccessIterator begin, RandomAccessIterator end, const T &value) |

`(obsolete) ` RandomAccessIterator | qLowerBound(RandomAccessIterator begin, RandomAccessIterator end, const T &value, LessThan lessThan) |

`(obsolete) ` typename Container::const_iterator | qLowerBound(const Container &container, const T &value) |

`(obsolete) ` void | qSort(RandomAccessIterator begin, RandomAccessIterator end) |

`(obsolete) ` void | qSort(RandomAccessIterator begin, RandomAccessIterator end, LessThan lessThan) |

`(obsolete) ` void | qSort(Container &container) |

`(obsolete) ` void | qStableSort(RandomAccessIterator begin, RandomAccessIterator end) |

`(obsolete) ` void | qStableSort(RandomAccessIterator begin, RandomAccessIterator end, LessThan lessThan) |

`(obsolete) ` void | qStableSort(Container &container) |

`(obsolete) ` void | qSwap(T &var1, T &var2) |

`(obsolete) ` RandomAccessIterator | qUpperBound(RandomAccessIterator begin, RandomAccessIterator end, const T &value) |

`(obsolete) ` RandomAccessIterator | qUpperBound(RandomAccessIterator begin, RandomAccessIterator end, const T &value, LessThan lessThan) |

`(obsolete) ` typename Container::const_iterator | qUpperBound(const Container &container, const T &value) |

## Function Documentation

### RandomAccessIterator qBinaryFind(RandomAccessIterator *begin*, RandomAccessIterator *end*, const T &*value*)

This function is obsolete. It is provided to keep old source code working. We strongly advise against using it in new code.

Use `std::binary_search`

or `std::lower_bound`

instead.

Performs a binary search of the range [*begin*, *end*) and returns the position of an occurrence of *value*. If there are no occurrences of *value*, returns *end*.

The items in the range [*begin*, *end*) must be sorted in ascending order; see qSort().

If there are many occurrences of the same value, any one of them could be returned. Use qLowerBound() or qUpperBound() if you need finer control.

Example:

QVector<int> vect; vect << 3 << 3 << 6 << 6 << 6 << 8; QVector<int>::iterator i = qBinaryFind(vect.begin(), vect.end(), 6); // i == vect.begin() + 2 (or 3 or 4)

This function requires the item type (in the example above, QString) to implement `operator<()`

.

**See also **qLowerBound(), qUpperBound(), and random access iterators.

### RandomAccessIterator qBinaryFind(RandomAccessIterator *begin*, RandomAccessIterator *end*, const T &*value*, LessThan *lessThan*)

This function is obsolete. It is provided to keep old source code working. We strongly advise against using it in new code.

This is an overloaded function.

Use `std::binary_search`

or `std::lower_bound`

instead.

Uses the *lessThan* function instead of `operator<()`

to compare the items.

Note that the items in the range must be sorted according to the order specified by the *lessThan* object.

### typename Container::const_iterator qBinaryFind(const Container &*container*, const T &*value*)

This function is obsolete. It is provided to keep old source code working. We strongly advise against using it in new code.

This is an overloaded function.

Use `std::binary_search`

or `std::lower_bound`

instead.

This is the same as qBinaryFind(*container*.begin(), *container*.end(), *value*);

### OutputIterator qCopy(InputIterator *begin1*, InputIterator *end1*, OutputIterator *begin2*)

Use `std::copy`

instead.

Copies the items from range [*begin1*, *end1*) to range [*begin2*, ...), in the order in which they appear.

The item at position *begin1* is assigned to that at position *begin2*; the item at position *begin1* + 1 is assigned to that at position *begin2* + 1; and so on.

Example:

QStringList list; list << "one" << "two" << "three"; QVector<QString> vect1(3); qCopy(list.begin(), list.end(), vect1.begin()); // vect: [ "one", "two", "three" ] QVector<QString> vect2(8); qCopy(list.begin(), list.end(), vect2.begin() + 2); // vect: [ "", "", "one", "two", "three", "", "", "" ]

**See also **qCopyBackward(), input iterators, and output iterators.

### BiIterator2 qCopyBackward(BiIterator1 *begin1*, BiIterator1 *end1*, BiIterator2 *end2*)

Use `std::copy_backward`

instead.

Copies the items from range [*begin1*, *end1*) to range [..., *end2*).

The item at position *end1* - 1 is assigned to that at position *end2* - 1; the item at position *end1* - 2 is assigned to that at position *end2* - 2; and so on.

Example:

QStringList list; list << "one" << "two" << "three"; QVector<QString> vect(5); qCopyBackward(list.begin(), list.end(), vect.end()); // vect: [ "", "", "one", "two", "three" ]

**See also **qCopy() and bidirectional iterators.

### void qCount(InputIterator *begin*, InputIterator *end*, const T &*value*, Size &*n*)

Use `std::count`

instead.

Returns the number of occurrences of *value* in the range [*begin*, *end*), which is returned in *n*. *n* is never initialized, the count is added to *n*. It is the caller's responsibility to initialize *n*.

Example:

QList<int> list; list << 3 << 3 << 6 << 6 << 6 << 8; int countOf6 = 0; qCount(list.begin(), list.end(), 6, countOf6); // countOf6 == 3 int countOf7 = 0; qCount(list.begin(), list.end(), 7, countOf7); // countOf7 == 0

This function requires the item type (in the example above, `int`

) to implement `operator==()`

.

**See also **input iterators.

### void qCount(const Container &*container*, const T &*value*, Size &*n*)

This is an overloaded function.

Use `std::count`

instead.

Instead of operating on iterators, as in the other overload, this function operates on the specified *container* to obtain the number of instances of *value* in the variable passed as a reference in argument *n*.

### bool qEqual(InputIterator1 *begin1*, InputIterator1 *end1*, InputIterator2 *begin2*)

Use `std::equal`

instead.

Compares the items in the range [*begin1*, *end1*) with the items in the range [*begin2*, ...). Returns `true`

if all the items compare equal; otherwise returns `false`

.

Example:

QStringList list; list << "one" << "two" << "three"; QVector<QString> vect(3); vect[0] = "one"; vect[1] = "two"; vect[2] = "three"; bool ret1 = qEqual(list.begin(), list.end(), vect.begin()); // ret1 == true vect[2] = "seven"; bool ret2 = qEqual(list.begin(), list.end(), vect.begin()); // ret2 == false

This function requires the item type (in the example above, QString) to implement `operator==()`

.

**See also **input iterators.

### void qFill(ForwardIterator *begin*, ForwardIterator *end*, const T &*value*)

Use `std::fill`

instead.

Fills the range [*begin*, *end*) with *value*.

Example:

QStringList list; list << "one" << "two" << "three"; qFill(list.begin(), list.end(), "eleven"); // list: [ "eleven", "eleven", "eleven" ] qFill(list.begin() + 1, list.end(), "six"); // list: [ "eleven", "six", "six" ]

**See also **qCopy() and forward iterators.

### void qFill(Container &*container*, const T &*value*)

This is an overloaded function.

Use `std::fill`

instead.

This is the same as qFill(*container*.begin(), *container*.end(), *value*);

### InputIterator qFind(InputIterator *begin*, InputIterator *end*, const T &*value*)

Use `std::find`

instead.

Returns an iterator to the first occurrence of *value* in a container in the range [*begin*, *end*). Returns *end* if *value* isn't found.

Example:

QStringList list; list << "one" << "two" << "three"; QStringList::iterator i1 = qFind(list.begin(), list.end(), "two"); // i1 == list.begin() + 1 QStringList::iterator i2 = qFind(list.begin(), list.end(), "seventy"); // i2 == list.end()

This function requires the item type (in the example above, QString) to implement `operator==()`

.

If the items in the range are in ascending order, you can get faster results by using qLowerBound() or qBinaryFind() instead of qFind().

**See also **qBinaryFind() and input iterators.

### typename Container::const_iterator qFind(const Container &*container*, const T &*value*)

This is an overloaded function.

Use `std::find`

instead.

This is the same as qFind(*container*.constBegin(), *container*.constEnd(), *value*);

### LessThan qGreater()

Use `std::greater`

instead.

Returns a functional object, or functor, that can be passed to qSort() or qStableSort().

Example:

QList<int> list; list << 33 << 12 << 68 << 6 << 12; qSort(list.begin(), list.end(), qGreater<int>()); // list: [ 68, 33, 12, 12, 6 ]

**See also **qLess<T>().

### LessThan qLess()

Use `std::less`

instead.

Returns a functional object, or functor, that can be passed to qSort() or qStableSort().

Example:

QList<int> list; list << 33 << 12 << 68 << 6 << 12; qSort(list.begin(), list.end(), qLess<int>()); // list: [ 6, 12, 12, 33, 68 ]

**See also **qGreater<T>().

### RandomAccessIterator qLowerBound(RandomAccessIterator *begin*, RandomAccessIterator *end*, const T &*value*)

Use `std::lower_bound`

instead.

Performs a binary search of the range [*begin*, *end*) and returns the position of the first occurrence of *value*. If no such item is found, returns the position where it should be inserted.

The items in the range [*begin*, *end*) must be sorted in ascending order; see qSort().

Example:

QList<int> list; list << 3 << 3 << 6 << 6 << 6 << 8; QList<int>::iterator i = qLowerBound(list.begin(), list.end(), 5); list.insert(i, 5); // list: [ 3, 3, 5, 6, 6, 6, 8 ] i = qLowerBound(list.begin(), list.end(), 12); list.insert(i, 12); // list: [ 3, 3, 5, 6, 6, 6, 8, 12 ]

This function requires the item type (in the example above, `int`

) to implement `operator<()`

.

qLowerBound() can be used in conjunction with qUpperBound() to iterate over all occurrences of the same value:

QVector<int> vect; vect << 3 << 3 << 6 << 6 << 6 << 8; QVector<int>::iterator begin6 = qLowerBound(vect.begin(), vect.end(), 6); QVector<int>::iterator end6 = qUpperBound(begin6, vect.end(), 6); QVector<int>::iterator i = begin6; while (i != end6) { *i = 7; ++i; } // vect: [ 3, 3, 7, 7, 7, 8 ]

**See also **qUpperBound() and qBinaryFind().

### RandomAccessIterator qLowerBound(RandomAccessIterator *begin*, RandomAccessIterator *end*, const T &*value*, LessThan *lessThan*)

This is an overloaded function.

Use `std::lower_bound`

instead.

Uses the *lessThan* function instead of `operator<()`

to compare the items.

Note that the items in the range must be sorted according to the order specified by the *lessThan* object.

### typename Container::const_iterator qLowerBound(const Container &*container*, const T &*value*)

This is an overloaded function.

Use `std::lower_bound`

instead.

For read-only iteration over containers, this function is broadly equivalent to qLowerBound(*container*.begin(), *container*.end(), value). However, since it returns a const iterator, you cannot use it to modify the container; for example, to insert items.

### void qSort(RandomAccessIterator *begin*, RandomAccessIterator *end*)

Use `std::sort`

instead.

Sorts the items in range [*begin*, *end*) in ascending order using the quicksort algorithm.

Example:

QList<int> list; list << 33 << 12 << 68 << 6 << 12; qSort(list.begin(), list.end()); // list: [ 6, 12, 12, 33, 68 ]

The sort algorithm is efficient on large data sets. It operates in linear-logarithmic time, O(*n* log *n*).

This function requires the item type (in the example above, `int`

) to implement `operator<()`

.

If neither of the two items is "less than" the other, the items are taken to be equal. It is then undefined which one of the two items will appear before the other after the sort.

**See also **qStableSort() and random access iterators.

### void qSort(RandomAccessIterator *begin*, RandomAccessIterator *end*, LessThan *lessThan*)

This is an overloaded function.

Use `std::sort`

instead.

Uses the *lessThan* function instead of `operator<()`

to compare the items.

For example, here's how to sort the strings in a QStringList in case-insensitive alphabetical order:

bool caseInsensitiveLessThan(const QString &s1, const QString &s2) { return s1.toLower() < s2.toLower(); } int doSomething() { QStringList list; list << "AlPha" << "beTA" << "gamma" << "DELTA"; qSort(list.begin(), list.end(), caseInsensitiveLessThan); // list: [ "AlPha", "beTA", "DELTA", "gamma" ] }

To sort values in reverse order, pass qGreater<T>() as the *lessThan* parameter. For example:

QList<int> list; list << 33 << 12 << 68 << 6 << 12; qSort(list.begin(), list.end(), qGreater<int>()); // list: [ 68, 33, 12, 12, 6 ]

If neither of the two items is "less than" the other, the items are taken to be equal. It is then undefined which one of the two items will appear before the other after the sort.

An alternative to using qSort() is to put the items to sort in a QMap, using the sort key as the QMap key. This is often more convenient than defining a *lessThan* function. For example, the following code shows how to sort a list of strings case insensitively using QMap:

QStringList list; list << "AlPha" << "beTA" << "gamma" << "DELTA"; QMap<QString, QString> map; foreach (const QString &str, list) map.insert(str.toLower(), str); list = map.values();

**See also **QMap.

### void qSort(Container &*container*)

This is an overloaded function.

Use `std::sort`

instead.

This is the same as qSort(*container*.begin(), *container*.end());

### void qStableSort(RandomAccessIterator *begin*, RandomAccessIterator *end*)

Use `std::stable_sort`

instead.

Sorts the items in range [*begin*, *end*) in ascending order using a stable sorting algorithm.

If neither of the two items is "less than" the other, the items are taken to be equal. The item that appeared before the other in the original container will still appear first after the sort. This property is often useful when sorting user-visible data.

Example:

QList<int> list; list << 33 << 12 << 68 << 6 << 12; qStableSort(list.begin(), list.end()); // list: [ 6, 12, 12, 33, 68 ]

The sort algorithm is efficient on large data sets. It operates in linear-logarithmic time, O(*n* log *n*).

This function requires the item type (in the example above, `int`

) to implement `operator<()`

.

**See also **qSort() and random access iterators.

### void qStableSort(RandomAccessIterator *begin*, RandomAccessIterator *end*, LessThan *lessThan*)

This is an overloaded function.

Use `std::stable_sort`

instead.

Uses the *lessThan* function instead of `operator<()`

to compare the items.

For example, here's how to sort the strings in a QStringList in case-insensitive alphabetical order:

bool caseInsensitiveLessThan(const QString &s1, const QString &s2) { return s1.toLower() < s2.toLower(); } int doSomething() { QStringList list; list << "AlPha" << "beTA" << "gamma" << "DELTA"; qStableSort(list.begin(), list.end(), caseInsensitiveLessThan); // list: [ "AlPha", "beTA", "DELTA", "gamma" ] }

Note that earlier versions of Qt allowed using a lessThan function that took its arguments by non-const reference. From 4.3 and on this is no longer possible, the arguments has to be passed by const reference or value.

To sort values in reverse order, pass qGreater<T>() as the *lessThan* parameter. For example:

QList<int> list; list << 33 << 12 << 68 << 6 << 12; qStableSort(list.begin(), list.end(), qGreater<int>()); // list: [ 68, 33, 12, 12, 6 ]

If neither of the two items is "less than" the other, the items are taken to be equal. The item that appeared before the other in the original container will still appear first after the sort. This property is often useful when sorting user-visible data.

### void qStableSort(Container &*container*)

This is an overloaded function.

Use `std::stable_sort`

instead.

This is the same as qStableSort(*container*.begin(), *container*.end());

### void qSwap(T &*var1*, T &*var2*)

Use `std::swap`

instead.

Exchanges the values of variables *var1* and *var2*.

Example:

double pi = 3.14; double e = 2.71; qSwap(pi, e); // pi == 2.71, e == 3.14

### RandomAccessIterator qUpperBound(RandomAccessIterator *begin*, RandomAccessIterator *end*, const T &*value*)

Use `std::upper_bound`

instead.

Performs a binary search of the range [*begin*, *end*) and returns the position of the one-past-the-last occurrence of *value*. If no such item is found, returns the position where the item should be inserted.

The items in the range [*begin*, *end*) must be sorted in ascending order; see qSort().

Example:

QList<int> list; list << 3 << 3 << 6 << 6 << 6 << 8; QList<int>::iterator i = qUpperBound(list.begin(), list.end(), 5); list.insert(i, 5); // list: [ 3, 3, 5, 6, 6, 6, 8 ] i = qUpperBound(list.begin(), list.end(), 12); list.insert(i, 12); // list: [ 3, 3, 5, 6, 6, 6, 8, 12 ]

This function requires the item type (in the example above, `int`

) to implement `operator<()`

.

qUpperBound() can be used in conjunction with qLowerBound() to iterate over all occurrences of the same value:

QVector<int> vect; vect << 3 << 3 << 6 << 6 << 6 << 8; QVector<int>::iterator begin6 = qLowerBound(vect.begin(), vect.end(), 6); QVector<int>::iterator end6 = qUpperBound(vect.begin(), vect.end(), 6); QVector<int>::iterator i = begin6; while (i != end6) { *i = 7; ++i; } // vect: [ 3, 3, 7, 7, 7, 8 ]

**See also **qLowerBound() and qBinaryFind().

### RandomAccessIterator qUpperBound(RandomAccessIterator *begin*, RandomAccessIterator *end*, const T &*value*, LessThan *lessThan*)

This is an overloaded function.

Use `std::upper_bound`

instead.

Uses the *lessThan* function instead of `operator<()`

to compare the items.

Note that the items in the range must be sorted according to the order specified by the *lessThan* object.

### typename Container::const_iterator qUpperBound(const Container &*container*, const T &*value*)

This is an overloaded function.

Use `std::upper_bound`

instead.

This is the same as qUpperBound(*container*.begin(), *container*.end(), *value*);