Brush up the container code snippets

- Bring iterator loops into a consistent form using auto and
  creating and end variable, use cbegin()/cend() where suitable
- Use (std::)endl instead of Qt::endl for iostreams
- Fix removed container conversion API (QList::fromSet, QSet::toList())
- Use range-based for instead of foreach
- Use initializer lists
- Use qPrintable(QString) for output to std::ostream
- Use qsizetype
- Remove some unused snippets

Complements f6b137bdc4.

Pick-to: 6.5
Change-Id: I8a167099cdb224f45b984fa834d46269144a7ef0
Reviewed-by: Christian Ehrlicher <ch.ehrlicher@gmx.de>
Reviewed-by: Ahmad Samir <a.samirh78@gmail.com>
Reviewed-by: Marc Mutz <marc.mutz@qt.io>

src/corelib/doc/snippets/code/doc_src_qset.cpp

@@ -34,18 +34,15 @@ while (i.hasNext()) {
 
 
 //! [5]
-QSet<QWidget *>::const_iterator i = set.constBegin();
-while (i != set.constEnd()) {
+for (auto i = set.cbegin(), end = set.cend(); != end; ++i)
     qDebug() << *i;
-    ++i;
-}
 //! [5]
 
 
 //! [6]
 QSet<QString> set;
 ...
-foreach (const QString &value, set)
+for (const auto &value : set)
     qDebug() << value;
 //! [6]
 
@@ -59,20 +56,18 @@ for (int i = 0; i < 20000; ++i)
 
 
 //! [8]
-QSet<QString> set;
-set << "January" << "February" << ... << "December";
+QSet<QString> set = {"January", "February", ... "December"}
 
-QSet<QString>::iterator i;
-for (i = set.begin(); i != set.end(); ++i)
+// i is a QSet<QString>::iterator
+for (auto i = set.begin(), end = set.end(); i != end; ++i)
     qDebug() << *i;
 //! [8]
 
 
 //! [9]
-QSet<QString> set;
-set << "January" << "February" << ... << "December";
+QSet<QString> set = {"January", "February", ... "December"};
 
-QSet<QString>::iterator i = set.begin();
+auto i = set.begin();
 while (i != set.end()) {
     if ((*i).startsWith('J')) {
         i = set.erase(i);
@@ -94,11 +89,10 @@ if (it != set.end())
 
 
 //! [11]
-QSet<QString> set;
-set << "January" << "February" << ... << "December";
+QSet<QString> set = {"January", "February", ... "December"};
 
-QSet<QString>::const_iterator i;
-for (i = set.begin(); i != set.end(); ++i)
+// i is QSet<QString>::const_iterator
+for (auto i = set.cbegin(), end = set.cend(); i != end; ++i)
     qDebug() << *i;
 //! [11]
 

src/corelib/doc/snippets/code/src_corelib_io_qsettings.cpp

@@ -138,10 +138,10 @@ QList<Login> logins;
 
 QSettings settings;
 settings.beginWriteArray("logins");
-for (int i = 0; i < logins.size(); ++i) {
+for (qsizetype i = 0; i < logins.size(); ++i) {
     settings.setArrayIndex(i);
-    settings.setValue("userName", list.at(i).userName);
-    settings.setValue("password", list.at(i).password);
+    settings.setValue("userName", logins.at(i).userName);
+    settings.setValue("password", logins.at(i).password);
 }
 settings.endArray();
 //! [16]

src/corelib/doc/snippets/code/src_corelib_serialization_qcborstream.cpp

@@ -198,7 +198,7 @@ using namespace Qt::StringLiterals;
    void appendMap(QCborStreamWriter &writer, const QMap<int, QString> &map)
    {
        writer.startMap(map.size());
-       for (auto it = map.begin(); it != map.end(); ++it) {
+       for (auto it = map.cbegin(), end = map.cend(); it != end; ++it) {
            writer.append(it.key());
            writer.append(it.value());
        }

src/corelib/doc/snippets/code/src_corelib_text_qbytearray.cpp

@@ -24,7 +24,7 @@ ba[4] = 0xca;
 //! [2]
 for (qsizetype i = 0; i < ba.size(); ++i) {
     if (ba.at(i) >= 'a' && ba.at(i) <= 'f')
-        cout << "Found character in range [a-f]" << Qt::endl;
+        cout << "Found character in range [a-f]" << endl;
 }
 //! [2]
 
@@ -41,7 +41,7 @@ x.replace(5, 3, "&");       // x == "rock & roll"
 QByteArray ba("We must be <b>bold</b>, very <b>bold</b>");
 qsizetype j = 0;
 while ((j = ba.indexOf("<b>", j)) != -1) {
-    cout << "Found <b> tag at index position " << j << Qt::endl;
+    cout << "Found <b> tag at index position " << j << endl;
     ++j;
 }
 //! [4]
@@ -79,7 +79,7 @@ QByteArray("abc").isEmpty();    // returns false
 QByteArray ba("Hello world");
 char *data = ba.data();
 while (*data) {
-    cout << "[" << *data << "]" << Qt::endl;
+    cout << "[" << *data << "]" << endl;
     ++data;
 }
 //! [8]

src/corelib/doc/snippets/code/src_corelib_thread_qfuture.cpp

@@ -6,7 +6,7 @@ QFuture<QString> future = ...;
 
 QFuture<QString>::const_iterator i;
 for (i = future.constBegin(); i != future.constEnd(); ++i)
-    cout << *i << Qt::endl;
+    cout << qPrintable(*i) << endl;
 //! [0]
 
 

src/corelib/doc/snippets/code/src_corelib_tools_qhash.cpp

@@ -42,7 +42,7 @@ QHash<int, QWidget *> hash;
 ...
 for (int i = 0; i < 1000; ++i) {
     if (hash[i] == okButton)
-        cout << "Found button at index " << i << Qt::endl;
+        cout << "Found button at index " << i << endl;
 }
 //! [6]
 
@@ -51,17 +51,14 @@ for (int i = 0; i < 1000; ++i) {
 QHashIterator<QString, int> i(hash);
 while (i.hasNext()) {
     i.next();
-    cout << i.key() << ": " << i.value() << Qt::endl;
+    cout << qPrintable(i.key()) << ": " << i.value() << endl;
 }
 //! [7]
 
 
 //! [8]
-QHash<QString, int>::const_iterator i = hash.cbegin();
-while (i != hash.cend()) {
-    cout << i.key() << ": " << i.value() << Qt::endl;
-    ++i;
-}
+for (auto i = map.cbegin(), end = map.cend(); != end; ++i)
+    cout << qPrintable(i.key()) << ": " << i.value() << endl;
 //! [8]
 
 
@@ -75,8 +72,8 @@ hash.insert("plenty", 2000);
 //! [12]
 QHash<QString, int> hash;
 ...
-foreach (int value, hash)
-    cout << value << Qt::endl;
+for (int value : std::as_const(hash))
+    cout << value << endl;
 //! [12]
 
 
@@ -138,7 +135,7 @@ QHash<QString, int> hash;
 ...
 QHash<QString, int>::const_iterator i = hash.find("HDR");
 while (i != hash.end() && i.key() == "HDR") {
-    cout << i.value() << Qt::endl;
+    cout << i.value() << endl;
     ++i;
 }
 //! [16]
@@ -151,15 +148,13 @@ hash.insert("February", 2);
 ...
 hash.insert("December", 12);
 
-QHash<QString, int>::iterator i;
-for (i = hash.begin(); i != hash.end(); ++i)
-    cout << i.key() << ": " << i.value() << Qt::endl;
+for (auto i = hash.cbegin(), end = hash.cend(); i != end; ++i)
+    cout << qPrintable(key()) << ": " << i.value() << endl;
 //! [17]
 
 
 //! [18]
-QHash<QString, int>::iterator i;
-for (i = hash.begin(); i != hash.end(); ++i)
+for (auto i = hash.begin(), end = hash.end(); i != end; ++i)
     i.value() += 2;
 //! [18]
 
@@ -181,9 +176,8 @@ hash.insert("February", 2);
 ...
 hash.insert("December", 12);
 
-QHash<QString, int>::const_iterator i;
-for (i = hash.cbegin(); i != hash.cend(); ++i)
-    cout << i.key() << ": " << i.value() << Qt::endl;
+for (auto i = hash.cbegin(), end = hash.cend(); i != end; ++i)
+    cout << qPrintable(i.key()) << ": " << i.value() << endl;
 //! [23]
 
 
@@ -204,24 +198,24 @@ hash3 = hash1 + hash2;
 
 //! [25]
 QList<int> values = hash.values("plenty");
-for (int i = 0; i < values.size(); ++i)
-    cout << values.at(i) << Qt::endl;
+for (auto i : std::as_const(values))
+    cout << i << endl;
 //! [25]
 
 
 //! [26]
-QMultiHash<QString, int>::iterator i = hash.find("plenty");
-while (i != hash.end() && i.key() == "plenty") {
-    cout << i.value() << Qt::endl;
+auto i = hash.constFind("plenty");
+while (i != hash.cend() && i.key() == "plenty") {
+    cout << i.value() << endl;
     ++i;
 }
 //! [26]
 
 //! [27]
-for (QHash<int, QString>::const_iterator it = hash.cbegin(), end = hash.cend(); it != end; ++it) {
-    cout << "The key: " << it.key() << Qt::endl
-    cout << "The value: " << it.value() << Qt::endl;
-    cout << "Also the value: " << (*it) << Qt::endl;
+for (auto it = hash.cbegin(), end = hash.cend(); it != end; ++it) {
+    cout << "The key: " << it.key() << endl;
+    cout << "The value: " << qPrintable(it.value()) << endl;
+    cout << "Also the value: " << qPrintable(*it) << endl;
 }
 //! [27]
 
@@ -294,7 +288,7 @@ hash.insert("February", 2);
 hash.insert("December", 12);
 
 for (auto [key, value] : hash.asKeyValueRange()) {
-    cout << key << ": " << value << Qt::endl;
+    cout << qPrintable(key) << ": " << value << endl;
     --value; // convert to JS month indexing
 }
 //! [34]
@@ -307,7 +301,7 @@ hash.insert("February", 2);
 hash.insert("December", 12);
 
 for (auto [key, value] : hash.asKeyValueRange()) {
-    cout << key << ": " << value << Qt::endl;
+    cout << qPrintable(key) << ": " << value << endl;
     --value; // convert to JS month indexing
 }
 //! [35]

src/corelib/doc/snippets/code/src_corelib_tools_qlist.cpp

@@ -26,7 +26,7 @@ if (list[0] == "Liz")
 //! [4]
 for (qsizetype i = 0; i < list.size(); ++i) {
     if (list.at(i) == "Alfonso")
-        cout << "Found Alfonso at position " << i << Qt::endl;
+        cout << "Found Alfonso at position " << i << endl;
 }
 //! [4]
 
@@ -34,7 +34,7 @@ for (qsizetype i = 0; i < list.size(); ++i) {
 //! [5]
 qsizetype i = list.indexOf("Harumi");
 if (i != -1)
-    cout << "First occurrence of Harumi is at position " << i << Qt::endl;
+    cout << "First occurrence of Harumi is at position " << i << endl;
 //! [5]
 
 
@@ -101,16 +101,14 @@ list.prepend("three");
 
 
 //! [9]
-QList<QString> list;
-list << "alpha" << "beta" << "delta";
+QList<QString> list = {"alpha", "beta", "delta"};
 list.insert(2, "gamma");
 // list: ["alpha", "beta", "gamma", "delta"]
 //! [9]
 
 
 //! [10]
-QList<double> list;
-list << 2.718 << 1.442 << 0.4342;
+QList<double> list = {2.718, 1.442, 0.4342};
 list.insert(1, 3, 9.9);
 // list: [2.718, 9.9, 9.9, 9.9, 1.442, 0.4342]
 //! [10]
@@ -127,8 +125,7 @@ list.fill("oh", 5);
 
 
 //! [12]
-QList<QString> list;
-list << "A" << "B" << "C" << "B" << "A";
+QList<QString> list{"A", "B", "C", "B", "A"};
 list.indexOf("B");            // returns 1
 list.indexOf("B", 1);         // returns 1
 list.indexOf("B", 2);         // returns 3
@@ -137,8 +134,7 @@ list.indexOf("X");            // returns -1
 
 
 //! [13]
-QList<QString> list;
-list << "A" << "B" << "C" << "B" << "A";
+QList<QString> list = {"A", "B", "C", "B", "A"};
 list.lastIndexOf("B");        // returns 3
 list.lastIndexOf("B", 3);     // returns 3
 list.lastIndexOf("B", 2);     // returns 1

src/corelib/doc/snippets/code/src_corelib_tools_qmap.cpp

@@ -42,7 +42,7 @@ QMap<int, QWidget *> map;
 ...
 for (int i = 0; i < 1000; ++i) {
     if (map[i] == okButton)
-        cout << "Found button at index " << i << Qt::endl;
+        cout << "Found button at index " << i << endl;
 }
 //! [6]
 
@@ -51,17 +51,14 @@ for (int i = 0; i < 1000; ++i) {
 QMapIterator<QString, int> i(map);
 while (i.hasNext()) {
     i.next();
-    cout << i.key() << ": " << i.value() << Qt::endl;
+    cout << qPrintable(i.key()) << ": " << i.value() << endl;
 }
 //! [7]
 
 
 //! [8]
-QMap<QString, int>::const_iterator i = map.cbegin();
-while (i != map.cend()) {
-    cout << i.key() << ": " << i.value() << Qt::endl;
-    ++i;
-}
+for (auto i = map.cbegin(), end = map.cend(); != end; ++i)
+    cout << qPrintable(i.key()) << ": " << i.value() << endl;
 //! [8]
 
 
@@ -75,8 +72,8 @@ map.insert("plenty", 2000);
 //! [12]
 QMap<QString, int> map;
 ...
-foreach (int value, map)
-    cout << value << Qt::endl;
+for (int value : std::as_const(map))
+    cout << value << endl;
 //! [12]
 
 
@@ -128,15 +125,13 @@ map.insert("February", 2);
 ...
 map.insert("December", 12);
 
-QMap<QString, int>::iterator i;
-for (i = map.begin(); i != map.end(); ++i)
-    cout << i.key() << ": " << i.value() << Qt::endl;
+for (auto i = map.cbegin(), end = map.cend(); i != end; ++i)
+    cout << qPrintable(i.key()) << ": " << i.value() << endl;
 //! [18]
 
 
 //! [19]
-QMap<QString, int>::iterator i;
-for (i = map.begin(); i != map.end(); ++i)
+for (auto i = map.begin(), end = map.end(); i != end; ++i)
     i.value() += 2;
 //! [19]
 
@@ -171,17 +166,16 @@ map.insert("February", 2);
 ...
 map.insert("December", 12);
 
-QMap<QString, int>::const_iterator i;
-for (i = map.cbegin(); i != map.cend(); ++i)
-    cout << i.key() << ": " << i.value() << Qt::endl;
+for (auto i = map.cbegin(), end = map.cend(); i != end; ++i)
+    cout << qPrintable(i.key()) << ": " << i.value() << endl;
 //! [24]
 
 
 //! [keyiterator1]
 for (QMap<int, QString>::const_iterator it = map.cbegin(), end = map.cend(); it != end; ++it) {
-    cout << "The key: " << it.key() << Qt::endl
-    cout << "The value: " << it.value() << Qt::endl;
-    cout << "Also the value: " << (*it) << Qt::endl;
+    cout << "The key: " << it.key() << endl;
+    cout << "The value: " << qPrintable(it.value()) << endl;
+    cout << "Also the value: " << qPrintable(*it) << endl;
 }
 //! [keyiterator1]
 
@@ -204,7 +198,7 @@ map.insert("February", 2);
 map.insert("December", 12);
 
 for (auto [key, value] : map.asKeyValueRange()) {
-    cout << key << ": " << value << Qt::endl;
+    cout << qPrintable(key) << ": " << value << endl;
     --value; // convert to JS month indexing
 }
 //! [28]

src/corelib/doc/snippets/code/src_corelib_tools_qmultimap.cpp

@@ -19,8 +19,8 @@ multimap.insert("c", -5);
 int num2 = multimap.value("a"); // 1
 int num3 = multimap.value("thirteen"); // not found; 0
 int num3 = 0;
-auto it = multimap.value("b");
-if (it != multimap.end()) {
+auto it = multimap.constFind("b");
+if (it != multimap.cend()) {
     num3 = it.value();
 }
 //! [3]
@@ -47,17 +47,14 @@ int timeout = multimap.value("TIMEOUT", 30);
 QMultiMapIterator<QString, int> i(multimap);
 while (i.hasNext()) {
     i.next();
-    cout << i.key() << ": " << i.value() << Qt::endl;
+    cout << qPrintable(i.key()) << ": " << i.value() << endl;
 }
 //! [7]
 
 
 //! [8]
-auto i = multimap.cbegin();
-while (i != multimap.cend()) {
-    cout << i.key() << ": " << i.value() << Qt::endl;
-    ++i;
-}
+for (auto i = multimap.cbegin(), end = multimap.cend(); i != end; ++i)
+    cout << qPrintable(i.key()) << ": " << i.value() << endl;
 //! [8]
 
 
@@ -70,22 +67,22 @@ multimap.insert("plenty", 2000);
 
 //! [10]
 QList<int> values = multimap.values("plenty");
-for (int i = 0; i < values.size(); ++i)
-    cout << values.at(i) << Qt::endl;
+for (auto i : std::as_const(values))
+    cout << i << endl;
 //! [10]
 
 
 //! [11]
-QMultiMap<QString, int>::iterator i = multimap.find("plenty");
+auto i = multimap.find("plenty");
 while (i != map.end() && i.key() == "plenty") {
-    cout << i.value() << Qt::endl;
+    cout << i.value() << endl;
     ++i;
 }
 
 // better:
 auto [i, end] = multimap.equal_range("plenty");
 while (i != end) {
-    cout << i.value() << Qt::endl;
+    cout << i.value() << endl;
     ++i;
 }
 //! [11]
@@ -94,8 +91,8 @@ while (i != end) {
 //! [12]
 QMap<QString, int> multimap;
 ...
-foreach (int value, multimap)
-    cout << value << Qt::endl;
+for (int value : std::as_const(multimap))
+    cout << value << endl;
 //! [12]
 
 
@@ -149,7 +146,7 @@ QMap<QString, int> multimap;
 QMap<QString, int>::const_iterator i = multimap.lowerBound("HDR");
 QMap<QString, int>::const_iterator upperBound = multimap.upperBound("HDR");
 while (i != upperBound) {
-    cout << i.value() << Qt::endl;
+    cout << i.value() << endl;
     ++i;
 }
 //! [16]
@@ -207,9 +204,8 @@ multimap.insert("February", 2);
 ...
 multimap.insert("December", 12);
 
-QMultiMap<QString, int>::const_iterator i;
-for (i = multimap.cbegin(); i != multimap.cend(); ++i)
-    cout << i.key() << ": " << i.value() << Qt::endl;
+for (auto i = multimap.cbegin(), end = multimap.cend(); i != end; ++i)
+    cout << qPrintable(i.key()) << ": " << i.value() << endl;
 //! [24]
 
 
@@ -228,10 +224,10 @@ map3 = map1 + map2;
 //! [25]
 
 //! [keyiterator1]
-for (QMultiMap<int, QString>::const_iterator it = multimap.cbegin(), end = multimap.cend(); it != end; ++it) {
-    cout << "The key: " << it.key() << Qt::endl
-    cout << "The value: " << it.value() << Qt::endl;
-    cout << "Also the value: " << (*it) << Qt::endl;
+for (auto it = multimap.cbegin(), end = multimap.cend(); it != end; ++it) {
+    cout << "The key: " << it.key() << endl
+    cout << "The value: " << qPrintable(it.value()) << endl;
+    cout << "Also the value: " << qPrintable(*it) << endl;
 }
 //! [keyiterator1]
 
@@ -254,7 +250,7 @@ map.insert("February", 2);
 map.insert("December", 12);
 
 for (auto [key, value] : map.asKeyValueRange()) {
-    cout << key << ": " << value << Qt::endl;
+    cout << qPrintable(key) << ": " << value << endl;
     --value; // convert to JS month indexing
 }
 //! [26]

src/corelib/doc/snippets/code/src_corelib_tools_qqueue.cpp

@@ -7,5 +7,5 @@ queue.enqueue(1);
 queue.enqueue(2);
 queue.enqueue(3);
 while (!queue.isEmpty())
-    cout << queue.dequeue() << Qt::endl;
+    cout << queue.dequeue() << endl;
 //! [0]

src/corelib/doc/snippets/qstringlist/main.cpp

@@ -66,7 +66,7 @@ Widget::Widget(QWidget *parent)
 
     result.clear();
 //! [12]
-    foreach (const QString &str, list) {
+    for (const auto &str : std::as_const(list)) {
         if (str.contains("Bill"))
             result += str;
     }

src/corelib/tools/qhash.cpp

@@ -1640,7 +1640,7 @@ size_t qHash(long double key, size_t seed) noexcept
     hash table, use \l{QMultiHash}.
 
     If you only need to extract the values from a hash (not the keys),
-    you can also use \l{foreach}:
+    you can also use range-based for:
 
     \snippet code/src_corelib_tools_qhash.cpp 12
 

src/corelib/tools/qmap.qdoc

@@ -97,7 +97,7 @@
     QMultiMap.
 
     If you only need to extract the values from a map (not the keys),
-    you can also use \l{foreach}:
+    you can also use range-based for:
 
     \snippet code/src_corelib_tools_qmap.cpp 12
 

src/corelib/tools/qmultimap.qdoc

@@ -92,7 +92,7 @@
     \snippet code/src_corelib_tools_qmultimap.cpp 11
 
     If you only need to extract the values from a map (not the keys),
-    you can also use \l{foreach}:
+    you can also use range-based for:
 
     \snippet code/src_corelib_tools_qmultimap.cpp 12
 

src/corelib/tools/qset.qdoc

@@ -46,7 +46,7 @@
     QSet is unordered, so an iterator's sequence cannot be assumed to
     be predictable. If ordering by key is required, use a QMap.
 
-    To navigate through a QSet, you can also use \l{foreach}:
+    To navigate through a QSet, you can also use range-based for:
 
     \snippet code/doc_src_qset.cpp 6