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Add support for first(n), last(n) and sliced() to QList 

This keeps the API symmetric with what we have in our string
classes.

Change-Id: I94c5b39b718ca2472f9ca645e7a42e4314636f67
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
bb10
Lars Knoll 2020-06-27 11:14:32 +02:00
parent 9a9a1a2a2e
commit 792cb3989a
3 changed files with 102 additions and 0 deletions
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23
src/corelib/tools/qlist.h
View File

@ -378,6 +378,29 @@ public:
inline bool endsWith(const T &t) const { return !isEmpty() && last() == t; }
QList<T> mid(qsizetype pos, qsizetype len = -1) const;
QList<T> first(qsizetype n) const
{
Q_ASSERT(size_t(n) <= size_t(size()));
return QList<T>(begin(), begin() + n);
}
QList<T> last(qsizetype n) const
{
Q_ASSERT(size_t(n) <= size_t(size()));
return QList<T>(end() - n, end());
}
QList<T> sliced(qsizetype pos) const
{
Q_ASSERT(size_t(pos) <= size_t(size()));
return QList<T>(begin() + pos, end());
}
QList<T> sliced(qsizetype pos, qsizetype n) const
{
Q_ASSERT(size_t(pos) <= size_t(size()));
Q_ASSERT(n >= 0);
Q_ASSERT(pos + n <= size());
return QList<T>(begin() + pos, begin() + pos + n);
}
T value(qsizetype i) const { return value(i, T()); }
T value(qsizetype i, const T &defaultValue) const;

49
src/corelib/tools/qlist.qdoc
View File

@ -202,6 +202,55 @@
are included.
*/
/*!
\fn template <typename T> QList<T> QList<T>::first(qsizetype n) const
\since 6.0
Returns a sub-list that contains the first \a n elements
of this list.
\note The behavior is undefined when \a n < 0 or \a n > size().
\sa last(), sliced()
*/
/*!
\fn template <typename T> QList<T> QList<T>::last(qsizetype n) const
\since 6.0
Returns a sub-list that contains the last \a n elements of this list.
\note The behavior is undefined when \a n < 0 or \a n > size().
\sa first(), sliced()
*/
/*!
\fn template <typename T> QList<T> QList<T>::sliced(qsizetype pos, qsizetype n) const
\since 6.0
Returns a sub-list that contains \a n elements of this list,
starting at position \a pos.
\note The behavior is undefined when \a pos < 0, \a n < 0,
or \a pos + \a n > size().
\sa first(), last()
*/
/*!
\fn template <typename T> QList<T> QList<T>::sliced(qsizetype pos) const
\since 6.0
\overload
Returns a sub-list that contains the elements of this list starting at
position \a pos and extending to its end.
\note The behavior is undefined when \a pos < 0 or \a pos > size().
\sa first(), last()
*/
/*! \fn template <typename T> QList<T>::QList()

30
tests/auto/corelib/tools/qlist/tst_qlist.cpp
View File

@ -267,6 +267,7 @@ private slots:
void last() const;
void lastIndexOf() const;
void mid() const;
void sliced() const;
void moveInt() const;
void moveMovable() const;
void moveCustom() const;
@ -1287,6 +1288,13 @@ void tst_QList::first() const
myvec.prepend(23);
QCOMPARE(myvec.first(), 23);
QCOMPARE(myvec.constFirst(), 23);
QCOMPARE(QList<int>().first(0), QList<int>());
QCOMPARE(myvec.first(0), QList<int>());
QCOMPARE(myvec.first(1), (QList<int>{23}));
QCOMPARE(myvec.first(2), (QList<int>{23, 42}));
QCOMPARE(myvec.first(3), myvec);
}
void tst_QList::constFirst() const
@ -1546,6 +1554,12 @@ void tst_QList::last() const
myvec.remove(3);
QCOMPARE(myvec.last(), QLatin1String("C"));
QCOMPARE(myvec.constLast(), QLatin1String("C"));
QCOMPARE(QList<QString>().last(0), QList<QString>());
QCOMPARE(myvec.last(0), QList<QString>());
QCOMPARE(myvec.last(1), (QList<QString>{QLatin1String("C")}));
QCOMPARE(myvec.last(2), (QList<QString>{QLatin1String("B"), QLatin1String("C")}));
QCOMPARE(myvec.last(3), myvec);
}
void tst_QList::constLast() const
@ -1648,6 +1662,22 @@ void tst_QList::mid() const
QCOMPARE(list.mid(4), QList<QString>() << "buck" << "hello" << "kitty");
}
void tst_QList::sliced() const
{
QList<QString> list;
list << "foo" << "bar" << "baz" << "bak" << "buck" << "hello" << "kitty";
QCOMPARE(QList<QString>().sliced(0), QList<QString>());
QCOMPARE(QList<QString>().sliced(0, 0), QList<QString>());
QCOMPARE(list.sliced(3, 3), QList<QString>() << "bak" << "buck" << "hello");
QCOMPARE(list.sliced(3), QList<QString>() << "bak" << "buck" << "hello" << "kitty");
QCOMPARE(list.sliced(6, 1), QList<QString>() << "kitty");
QCOMPARE(list.sliced(6), QList<QString>() << "kitty");
QCOMPARE(list.sliced(0, list.size()), list);
QCOMPARE(list.sliced(0), list);
QCOMPARE(list.sliced(4), QList<QString>() << "buck" << "hello" << "kitty");
}
template <typename T>
void tst_QList::qhash() const
{