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<td align="right" valign="top" width="230"><img src="images/trolltech-logo.png" align="right" width="203" height="32" border="0" /></td></tr></table><h1 align="center"><QtAlgorithms> - Generic Algorithms</h1>

The <QtAlgorithms> header file provides generic template-based algorithms. <a href="#details">More...</a>

<h3>Functions</h3>

<ul>

<li><div class="fn"/>RandomAccessIterator <a href="qtalgorithms.html#qBinaryFind">qBinaryFind</a> ( RandomAccessIterator begin, RandomAccessIterator end, const T & value )</li>

<li><div class="fn"/>OutputIterator <a href="qtalgorithms.html#qCopy">qCopy</a> ( InputIterator begin1, InputIterator end1, OutputIterator begin2 )</li>

<li><div class="fn"/>BiIterator2 <a href="qtalgorithms.html#qCopyBackward">qCopyBackward</a> ( BiIterator1 begin1, BiIterator1 end1, BiIterator2 end2 )</li>

<li><div class="fn"/>void <a href="qtalgorithms.html#qCount">qCount</a> ( InputIterator begin, InputIterator end, const T & value, Size & n )</li>

<li><div class="fn"/>void <a href="qtalgorithms.html#qDeleteAll">qDeleteAll</a> ( ForwardIterator begin, ForwardIterator end )</li>

<li><div class="fn"/>void <a href="qtalgorithms.html#qDeleteAll-2">qDeleteAll</a> ( const Container & c )</li>

<li><div class="fn"/>bool <a href="qtalgorithms.html#qEqual">qEqual</a> ( InputIterator1 begin1, InputIterator1 end1, InputIterator2 begin2 )</li>

<li><div class="fn"/>void <a href="qtalgorithms.html#qFill">qFill</a> ( ForwardIterator begin, ForwardIterator end, const T & value )</li>

<li><div class="fn"/>InputIterator <a href="qtalgorithms.html#qFind">qFind</a> ( InputIterator begin, InputIterator end, const T & value )</li>

<li><div class="fn"/>RandomAccessIterator <a href="qtalgorithms.html#qLowerBound">qLowerBound</a> ( RandomAccessIterator begin, RandomAccessIterator end, const T & value )</li>

<li><div class="fn"/>void <a href="qtalgorithms.html#qSort">qSort</a> ( BiIterator begin, BiIterator end )</li>

<li><div class="fn"/>void <a href="qtalgorithms.html#qSort-2">qSort</a> ( BiIterator begin, BiIterator end, LessThan lessThan )</li>

<li><div class="fn"/>void <a href="qtalgorithms.html#qSort-3">qSort</a> ( Container & container )</li>

<li><div class="fn"/>void <a href="qtalgorithms.html#qStableSort">qStableSort</a> ( BiIterator begin, BiIterator end )</li>

<li><div class="fn"/>void <a href="qtalgorithms.html#qStableSort-2">qStableSort</a> ( BiIterator begin, BiIterator end, LessThan lessThan )</li>

<li><div class="fn"/>void <a href="qtalgorithms.html#qStableSort-3">qStableSort</a> ( Container & container )</li>

<li><div class="fn"/>void <a href="qtalgorithms.html#qSwap">qSwap</a> ( T & var1, T & var2 )</li>

<li><div class="fn"/>RandomAccessIterator <a href="qtalgorithms.html#qUpperBound">qUpperBound</a> ( RandomAccessIterator begin, RandomAccessIterator end, const T & value )</li>

</ul>

<hr />

<h2>Detailed Description</h2>

The <QtAlgorithms> header file provides generic template-based algorithms.

Qt provides a number of global template functions in <tt><QtAlgorithms></tt> that work on containers and perform well-know algorithms. You can use these algorithms with any <a href="containers.html#container-class">container class</a> that provides STL-style iterators, including Qt's <a href="qlist.html">QList</a>, <a href="qlinkedlist.html">QLinkedList</a>, <a href="qvector.html">QVector</a>, <a href="qmap.html">QMap</a>, and <a href="qhash.html">QHash</a> classes.

These functions have taken their inspiration from similar functions available in the STL <tt><algorithm></tt> header. Most of them have a direct STL equivalent; for example, <a href="qtalgorithms.html#qCopyBackward">qCopyBackward</a>() is the same as STL's copy_backward() algorithm.

If STL is available on all your target platforms, you can use the STL algorithms instead of their Qt counterparts. One reason why you might want to use the the STL algorithms is that STL provides dozens and dozens of algorithms, whereas Qt only provides the most important ones, making no attempt to duplicate functionality that is already provided by the C++ standard.

Most algorithms take <a href="containers.html#stl-style-iterators">STL-style iterators</a> as parameters. The algorithms are generic in the sense that they aren't bound to a specific iterator class; you can use them with any iterators that meet a certain set of requirements.

Let's take the <a href="qtalgorithms.html#qFill">qFill</a>() algorithm as an example. Unlike <a href="qvector.html">QVector</a>, <a href="qlist.html">QList</a> has no fill() function that can be used to fill a list with a particular value. If you need that functionality, you can use <a href="qtalgorithms.html#qFill">qFill</a>():

<pre>  QList<QString> list;

list << "one" << "two" << "three";

qFill(list.begin(), list.end(), "eleven");

// list: [ "eleven", "eleven", "eleven" ]</pre>

<a href="qtalgorithms.html#qFill">qFill</a>() takes a begin iterator, an end iterator, and a value. In the example above, we pass <tt>list.begin()</tt> and <tt>list.end()</tt> as the begin and end iterators, but this doesn't have to be the case:

<pre>  qFill(list.begin() + 1, list.end(), "six");

// list: [ "eleven", "six", "six" ]</pre>

The various algorithms have different requirements for the iterators they accept. For example, <a href="qtalgorithms.html#qFill">qFill</a>() accepts two <a href="#input-iterators">input iterators</a>, the most minimal requirement for an iterator type. The requirements are specified for every algorithm. If an iterator of the wrong type is passed (for example, <a href="qlist.html#ConstIterator-typedef">QList::ConstIterator</a> is passed as an <a href="#output-iterators">output iterator</a>), you will always get a compiler error, although not necessarily a very informative one.

Some algorithms have special requirements on the value type stored in the containers. For example, <a href="qtalgorithms.html#qEqual">qEqual</a>() requires that the value type supports operator==(), which it uses to compare items. Similarly, <a href="qtalgorithms.html#qDeleteAll">qDeleteAll</a>() requires that the value type is a non-const pointer type (for example, <a href="qwidget.html">QWidget</a> *). The value type requirements are specified for each algorithm, and the compiler will produce an error if a requirement isn't met.

<a name="binaryfind-example"></a>The generic algorithms can be used on other container classes than those provided by Qt and STL. The syntax of STL-style iterators is modeled after C++ pointers, so it's possible to use plain arrays as containers and plain pointers as iterators. A common idiom is to use <a href="qtalgorithms.html#qBinaryFind">qBinaryFind</a>() together with two static arrays: one that contains a list of keys, and another that contains a list of associated values. For example, the following code will look up an HTML entity (e.g., <tt>&amp</tt>;) in the <tt>name_table</tt> array and return the corresponding Unicode value from the <tt>value_table</tt> if the entity is recognized:

<pre>  QChar resolveEntity(const QString &entity)

{

static const QLatin1String name_table[] = {

"AElig", "Aacute", ..., "zwnj"

};

static const ushort value_table[] = {

0x0061, 0x00c1, ..., 0x200c

};

int N = sizeof(name_table) / sizeof(name_table[0]);

const QLatin1String *name = qBinaryFind(name_table, name_table + N,

entity);

int index = name - name_table;

if (index == N)

return QChar();

return QChar(value_table[index]);

}</pre>

This kind of code is for advanced users only; for most applications, a <a href="qmap.html">QMap</a>- or <a href="qhash.html">QHash</a>-based approach would work just as well:

<pre>  QChar resolveEntity(const QString &entity)

{

static QMap<QString, int> entityMap;

if (!entityMap) {

entityMap.insert("AElig", 0x0061);

entityMap.insert("Aacute", 0x00c1);

...

entityMap.insert("zwnj", 0x200c);

}

return QChar(entityMap.value(entity));

}</pre>

<h3>Types of Iterators</h3>

The algorithms have certain requirements on the iterator types they accept, and these are specified individually for each function. The compiler will produce an error if a requirement isn't met.

<h4>Input Iterators</h4>

100

An input iterator is an iterator that can be used for reading data sequentially from a container. It must provide the following operators: <tt>==</tt> and <tt>!=</tt> for comparing two iterators, unary <tt>*</tt> for retrieving the value stored in the item, and prefix <tt>++</tt> for advancing to the next item.

101

The Qt containers' iterator types (const and non-const) are all input iterators.

102

103

<h4>Output Iterators</h4>

104

An output iterator is an iterator that can be used for writing data sequentially to a container or to some output stream. It must provide the following operators: unary <tt>*</tt> for writing a value (i.e., <tt>*it = val</tt>) and prefix <tt>++</tt> for advancing to the next item.

105

The Qt containers' non-const iterator types are all output iterators.

106

107

<h4>Forward Iterators</h4>

108

A forward iterator is an iterator that meets the requirements of both input iterators and output iterators.

109

The Qt containers' non-const iterator types are all forward iterators.

110

111

<h4>Bidirectional Iterators</h4>

112

A bidirectional iterator is an iterator that meets the requirements of forward iterators but that in addition supports prefix <tt>--</tt> for iterating backward.

113

The Qt containers' non-const iterator types are all bidirectional iterators.

114

115

<h4>Random Access Iterators</h4>

116

The last category, random access iterators, is the most powerful type of iterator. It supports all the requirements of a bidirectional iterator, and supports the following operations:

117

118

<tr valign="top" bgcolor="#f0f0f0"><td><tt>i += n</tt></td><td>advances iterator <tt>i</tt> by <tt>n</tt> positions</td></tr>

119

<tr valign="top" bgcolor="#e0e0e0"><td><tt>i -= n</tt></td><td>moves iterator <tt>i</tt> back by <tt>n</tt> positions</td></tr>

120

<tr valign="top" bgcolor="#f0f0f0"><td><tt>i + n</tt> or <tt>n + i</tt></td><td>returns the iterator for the item <tt>n</tt> positions ahead of iterator <tt>i</tt></td></tr>

121

<tr valign="top" bgcolor="#e0e0e0"><td><tt>i - n</tt></td><td>returns the iterator for the item <tt>n</tt> positions behind of iterator <tt>i</tt></td></tr>

122

<tr valign="top" bgcolor="#f0f0f0"><td><tt>i - j</tt></td><td>returns the number of items between iterators <tt>i</tt> and <tt>j</tt></td></tr>

123

124

<tr valign="top" bgcolor="#f0f0f0"><td><tt>i < j</tt></td><td>returns true if iterator <tt>j</tt> comes after iterator <tt>i</tt></td></tr>

125

</table>

126

<a href="qlist.html">QList</a>, <a href="qlinkedlist.html">QLinkedList</a>, and <a href="qvector.html">QVector</a>'s non-const iterator types are random access iterators.

127

See also <a href="containers.html#container-classes">container classes</a> and <a href="qtglobal.html"><QtGlobal></a>.

128

<hr />

129

<h2>Function Documentation</h2>

130

<h3 class="fn"><a name="qBinaryFind"></a>RandomAccessIterator qBinaryFind ( RandomAccessIterator begin, RandomAccessIterator end, const T & value )</h3>

131

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.

132

The items in the range [begin, end) must be sorted in ascending order; see <a href="qtalgorithms.html#qSort">qSort</a>().

133

If there are many occurrences of the same value, any one of them could be returned. Use <a href="qtalgorithms.html#qLowerBound">qLowerBound</a>() or <a href="qtalgorithms.html#qUpperBound">qUpperBound</a>() if you need finer control.

134

Example:

135

<pre>  QVector<int> vect;

136

vect << 3 << 3 << 6 << 6 << 6 << 8;

137

138

QVector<int>::Iterator i =

139

qBinaryFind(vect.begin(), vect.end(), 6);

140

// i == vect.begin() + 2 (or 3 or 4)</pre>

141

This function requires the item type (in the example above, <a href="qstring.html">QString</a>) to implement <tt>operator<()</tt>.

142

See the <a href="qtalgorithms.html#binaryfind-example">detailed description</a> for an example usage.

143

See also <a href="qtalgorithms.html#qLowerBound">qLowerBound</a>(), <a href="qtalgorithms.html#qUpperBound">qUpperBound</a>(), and <a href="qtalgorithms.html#random-access-iterators">random access iterators</a>.

144

<h3 class="fn"><a name="qCopy"></a>OutputIterator qCopy ( InputIterator begin1, InputIterator end1, OutputIterator begin2 )</h3>

145

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

146

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.

147

Example:

148

<pre>  QList<QString> list;

149

list << "one" << "two" << "three";

150

151

QVector<QString> vect1(3);

152

qCopy(list.begin(), list.end(), vect1.begin());

153

// vect: [ "one", "two", "three" ]

154

155

QVector<QString> vect2(8);

156

qCopy(list.begin(), list.end(), vect2.begin() + 2);

157

// vect: [ "", "", "one", "two", "three", "", "", "" ]</pre>

158

See also <a href="qtalgorithms.html#qCopyBackward">qCopyBackward</a>(), <a href="qtalgorithms.html#input-iterators">input iterators</a>, and <a href="qtalgorithms.html#output-iterators">output iterators</a>.

159

<h3 class="fn"><a name="qCopyBackward"></a>BiIterator2 qCopyBackward ( BiIterator1 begin1, BiIterator1 end1, BiIterator2 end2 )</h3>

160

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

161

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.

162

Example:

163

<pre>  QList<QString> list;

164

list << "one" << "two" << "three";

165

166

QVector<QString> vect(5);

167

qCopyBackward(list.begin(), list.end(), vect.end());

168

// vect: [ "", "", "one", "two", "three" ]</pre>

169

See also <a href="qtalgorithms.html#qCopy">qCopy</a>() and <a href="qtalgorithms.html#bidirectional-iterators">bidirectional iterators</a>.

170

<h3 class="fn"><a name="qCount"></a>void qCount ( InputIterator begin, InputIterator end, const T & value, Size & n )</h3>

171

Sets n to the number of occurrences of value in the range [begin, end).

172

Example:

173

<pre>  QList<int> list;

174

list << 3 << 3 << 6 << 6 << 6 << 8;

175

176

int countOf6;

177

qCount(list.begin(), list.end(), 6, countOf6);

178

// countOf6 == 3

179

180

int countOf7;

181

qCount(list.begin(), list.end(), 7, countOf7);

182

// countOf7 == 0</pre>

183

This function requires the item type (in the example above, <tt>int</tt>) to implement <tt>operator==()</tt>.

184

See also <a href="qtalgorithms.html#input-iterators">input iterators</a>.

185

<h3 class="fn"><a name="qDeleteAll"></a>void qDeleteAll ( ForwardIterator begin, ForwardIterator end )</h3>

186

Deletes all the items in the range [begin, end) using the C++ <tt>delete</tt> operator. The item type must be a pointer type (for example, <tt>QWidget *</tt>).

187

Example:

188

<pre>  QList<Employee *> list;

189

list.append(new Employee("Blackpool", "Stephen"));

190

list.append(new Employee("Twist", "Oliver"));

191

192

qDeleteAll(list.begin(), list.end());

193

list.clear();</pre>

194

Notice that qDeleteAll() doesn't remove the items from the container; it merely calls <tt>delete</tt> on them. In the example above, we call clear() on the container to remove the items.

195

See also <a href="qtalgorithms.html#forward-iterators">forward iterators</a>.

196

<h3 class="fn"><a name="qDeleteAll-2"></a>void qDeleteAll ( const Container & c )</h3>

197

This is an overloaded member function, provided for convenience. It behaves essentially like the above function.

198

This is the same as qDeleteAll(c.begin(), c.end()).

199

<h3 class="fn"><a name="qEqual"></a>bool qEqual ( InputIterator1 begin1, InputIterator1 end1, InputIterator2 begin2 )</h3>

200

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.

201

Example:

202

<pre>  QList<QString> list;

203

list << "one" << "two << "three";

204

205

QVector<QString> vect[3];

206

vect[0] = "one";

207

vect[1] = "two";

208

vect[2] = "three";

209

210

bool ret1 = qEqual(list.begin(), list.end(), vect.begin());

211

// ret1 == true

212

213

vect[2] = "seven";

214

bool rec2 = qEqual(list.begin(), list.end(), vect.begin());

215

// ret2 == false</pre>

216

This function requires the item type (in the example above, <a href="qstring.html">QString</a>) to implement <tt>operator==()</tt>.

217

See also <a href="qtalgorithms.html#input-iterators">input iterators</a>.

218

<h3 class="fn"><a name="qFill"></a>void qFill ( ForwardIterator begin, ForwardIterator end, const T & value )</h3>

219

Fills the range [begin, end) with value.

220

Example:

221

<pre>  QList<QString> list;

222

list << "one" << "two" << "three";

223

224

qFill(list.begin(), list.end(), "eleven");

225

// list: [ "eleven", "eleven", "eleven" ]

226

227

qFill(list.begin() + 1, list.end(), "six");

228

// list: [ "eleven", "six", "six" ]</pre>

229

See also <a href="qtalgorithms.html#qCopy">qCopy</a>() and <a href="qtalgorithms.html#forward-iterators">forward iterators</a>.

230

<h3 class="fn"><a name="qFind"></a>InputIterator qFind ( InputIterator begin, InputIterator end, const T & value )</h3>

231

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

232

Example:

233

<pre>  QList<QString> list;

234

list << "one" << "two" << "three";

235

236

QList<QString>::Iterator i1 = qFind(list.begin(), list.end(),

237

"two");

238

// i1 == list.begin() + 1

239

240

QList<QString>::Iterator i2 = qFind(list.begin(), list.end(),

241

"seventy");

242

// i2 == list.end()</pre>

243

This function requires the item type (in the example above, <a href="qstring.html">QString</a>) to implement <tt>operator==()</tt>.

244

If the items in the range are in ascending order, you can get faster results by using <a href="qtalgorithms.html#qLowerBound">qLowerBound</a>() or <a href="qtalgorithms.html#qBinaryFind">qBinaryFind</a>() instead of qFind().

245

See also <a href="qtalgorithms.html#qBinaryFind">qBinaryFind</a>() and <a href="qtalgorithms.html#input-iterators">input iterators</a>.

246

<h3 class="fn"><a name="qLowerBound"></a>RandomAccessIterator qLowerBound ( RandomAccessIterator begin, RandomAccessIterator end, const T & value )</h3>

247

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

248

The items in the range [begin, end) must be sorted in ascending order; see <a href="qtalgorithms.html#qSort">qSort</a>().

249

Example:

250

<pre>  QList<int> list;

251

list << 3 << 3 << 6 << 6 << 6 << 8;

252

253

QList<int>::Iterator i = qLowerBound(list.begin(), list.end(), 5);

254

list.insert(i, 5);

255

// list: [ 3, 3, 5, 6, 6, 6, 8 ]

256

257

i = qLowerBound(list.begin(), list.end(), 12);

258

list.insert(i, 12);

259

// list: [ 3, 3, 5, 6, 6, 6, 8, 12 ]</pre>

260

This function requires the item type (in the example above, <tt>int</tt>) to implement <tt>operator<()</tt>.

261

qLowerBound() can be used in conjunction with <a href="qtalgorithms.html#qUpperBound">qUpperBound</a>() to iterate over all occurrences of the same value:

262

<pre>  QVector<int> vect;

263

vect << 3 << 3 << 6 << 6 << 6 << 8;

264

QVector<int>::Iterator begin6 =

265

qLowerBound(vect.begin(), vect.end(), 6);

266

QVector<int>::Iterator end6 =

267

qUpperBound(begin6, vect.end(), 6);

268

269

QVector<int>::Iterator i = begin6;

270

while (i != end6) {

271

*i = 7;

272

++i;

273

}

274

// vect: [ 3, 3, 7, 7, 7, 8 ]</pre>

275

See also <a href="qtalgorithms.html#qUpperBound">qUpperBound</a>() and <a href="qtalgorithms.html#qBinaryFind">qBinaryFind</a>().

276

<h3 class="fn"><a name="qSort"></a>void qSort ( BiIterator begin, BiIterator end )</h3>

277

Sorts the items in range [begin, end) in ascending order using the heap sort algorithm.

278

Example:

279

<pre>  QList<int> list;

280

list << 33 << 12 << 68 << 6 << 12;

281

qSort(list.begin(), list.end());

282

// list: [ 6, 12, 12, 33, 68 ]</pre>

283

The sort algorithm is efficient on large data sets. It operates in <a href="containers.html#linear-logarithmic-time">linear-logarithmic time</a>, O(n log n).

284

This function requires the item type (in the example above, <tt>int</tt>) to implement <tt>operator<()</tt>.

285

If of two items neither 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.

286

See also <a href="qtalgorithms.html#qStableSort">qStableSort</a>() and <a href="qtalgorithms.html#bidirectional-iterators">bidirectional iterators</a>.

287

<h3 class="fn"><a name="qSort-2"></a>void qSort ( BiIterator begin, BiIterator end, LessThan lessThan )</h3>

288

This is an overloaded member function, provided for convenience. It behaves essentially like the above function.

289

Uses the lessThan function instead of <tt>operator<()</tt> to compare the items.

290

For example, here's how to sort the strings in a <a href="qlist.html">QList</a><<a href="qstring.html">QString</a>> in case-insensitive alphabetical order:

291

<pre>  bool caseInsensitiveLessThan(const QString &s1, const QString &s2)

292

{

293

return s1.toLower() < s2.toLower();

294

}

295

296

int doSomething()

297

{

298

QList<QString> list;

299

list << "AlPha" << "beTA" << "gamma" << "DELTA";

300

qSort(list.begin(), list.end(), caseInsensitiveLessThan);

301

// list: [ "AlPha", "beTA", "DELTA", "gamma" ]

302

}</pre>

303

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

304

<pre>  QList<int> list;

305

list << 33 << 12 << 68 << 6 << 12;

306

qSort(list.begin(), list.end(), qGreater<int>());

307

// list: [ 68, 33, 12, 12, 6 ]</pre>

308

If of two items neither 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.

309

<h3 class="fn"><a name="qSort-3"></a>void qSort ( Container & container )</h3>

310

This is an overloaded member function, provided for convenience. It behaves essentially like the above function.

311

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

312

<h3 class="fn"><a name="qStableSort"></a>void qStableSort ( BiIterator begin, BiIterator end )</h3>

313

Sorts the items in range [begin, end) in ascending order using the heap sort algorithm.

314

Example:

315

<pre>  QList<int> list;

316

list << 33 << 12 << 68 << 6 << 12;

317

qStableSort(list.begin(), list.end());

318

// list: [ 6, 12, 12, 33, 68 ]</pre>

319

The sort algorithm is efficient on large data sets. It operates in <a href="containers.html#linear-logarithmic-time">linear-logarithmic time</a>, O(n log n).

320

This function requires the item type (in the example above, <tt>int</tt>) to implement <tt>operator<()</tt>.

321

If of two items neither 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.

322

See also <a href="qtalgorithms.html#qSort">qSort</a>() and <a href="qtalgorithms.html#bidirectional-iterators">bidirectional iterators</a>.

323

<h3 class="fn"><a name="qStableSort-2"></a>void qStableSort ( BiIterator begin, BiIterator end, LessThan lessThan )</h3>

324

This is an overloaded member function, provided for convenience. It behaves essentially like the above function.

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Uses the lessThan function instead of <tt>operator<()</tt> to compare the items.

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For example, here's how to sort the strings in a <a href="qlist.html">QList</a><<a href="qstring.html">QString</a>> in case-insensitive alphabetical order:

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<pre>  bool caseInsensitiveLessThan(const QString &s1, const QString &s2)

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{

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return s1.toLower() < s2.toLower();

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}

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int doSomething()

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{

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QList<QString> list;

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list << "AlPha" << "beTA" << "gamma" << "DELTA";

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qStableSort(list.begin(), list.end(), caseInsensitiveLessThan);

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// list: [ "AlPha", "beTA", "DELTA", "gamma" ]

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}</pre>

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

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<pre>  QList<int> list;

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list << 33 << 12 << 68 << 6 << 12;

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qStableSort(list.begin(), list.end(), qGreater<int>());

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// list: [ 68, 33, 12, 12, 6 ]</pre>

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If of two items neither 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.

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<h3 class="fn"><a name="qStableSort-3"></a>void qStableSort ( Container & container )</h3>

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This is an overloaded member function, provided for convenience. It behaves essentially like the above function.

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

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<h3 class="fn"><a name="qSwap"></a>void qSwap ( T & var1, T & var2 )</h3>

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Exchanges the values of variables var1 and var2.

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Example:

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<pre>  double pi = 3.14;

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double e = 2.71;

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qSwap(pi, e);

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// pi == 2.71, e == 3.14</pre>

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<h3 class="fn"><a name="qUpperBound"></a>RandomAccessIterator qUpperBound ( RandomAccessIterator begin, RandomAccessIterator end, const T & value )</h3>

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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.

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The items in the range [begin, end) must be sorted in ascending order; see <a href="qtalgorithms.html#qSort">qSort</a>().

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Example:

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<pre>  QList<int> list;

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list << 3 << 3 << 6 << 6 << 6 << 8;

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QList<int>::Iterator i = qUpperBound(list.begin(), list.end(), 5);

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list.insert(i, 5);

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// list: [ 3, 3, 5, 6, 6, 6, 8 ]

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i = qUpperBound(list.begin(), list.end(), 12);

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list.insert(i, 12);

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// list: [ 3, 3, 5, 6, 6, 6, 8, 12 ]</pre>

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This function requires the item type (in the example above, <tt>int</tt>) to implement <tt>operator<()</tt>.

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qUpperBound() can be used in conjunction with <a href="qtalgorithms.html#qLowerBound">qLowerBound</a>() to iterate over all occurrences of the same value:

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<pre>  QVector<int> vect;

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vect << 3 << 3 << 6 << 6 << 6 << 8;

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QVector<int>::Iterator begin6 =

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qLowerBound(vect.begin(), vect.end(), 6);

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QVector<int>::Iterator end6 =

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qUpperBound(vect.begin(), vect.end(), 6);

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QVector<int>::Iterator i = begin6;

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while (i != end6) {

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*i = 7;

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++i;

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}

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// vect: [ 3, 3, 7, 7, 7, 8 ]</pre>

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See also <a href="qtalgorithms.html#qLowerBound">qLowerBound</a>() and <a href="qtalgorithms.html#qBinaryFind">qBinaryFind</a>().

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<td width="40%" align="center"><a href="trademarks.html">Trademarks</a></td>

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</tr></table></div></address></body>

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