QSet: add erase_if

[ChangeLog][QtCore][QSet] Added erase_if() for consistent
container erasure. Added removeIf() as a method.

Change-Id: I4af57b654036aa08bee3f769ab2f60be37115094
Reviewed-by: Andrei Golubev <andrei.golubev@qt.io>
Reviewed-by: Lars Knoll <lars.knoll@qt.io>

src/corelib/tools/qcontainertools_impl.h

@@ -198,6 +198,23 @@ auto sequential_erase_if(Container &c, Predicate &pred)
     return result;
 }
 
+template <typename T, typename Predicate>
+qsizetype qset_erase_if(QSet<T> &set, Predicate &pred)
+{
+    qsizetype result = 0;
+    auto it = set.begin();
+    const auto e = set.end();
+    while (it != e) {
+        if (pred(*it)) {
+            ++result;
+            it = set.erase(it);
+        } else {
+            ++it;
+        }
+    }
+    return result;
+}
+
 } // namespace QtPrivate
 
 QT_END_NAMESPACE

src/corelib/tools/qset.h

@@ -93,6 +93,12 @@ public:
 
     inline bool remove(const T &value) { return q_hash.remove(value) != 0; }
 
+    template <typename Pred>
+    inline qsizetype removeIf(Pred predicate)
+    {
+        return QtPrivate::qset_erase_if(*this, predicate);
+    }
+
     inline bool contains(const T &value) const { return q_hash.contains(value); }
 
     bool contains(const QSet<T> &set) const;
@@ -361,6 +367,12 @@ public:
 };
 #endif // QT_NO_JAVA_STYLE_ITERATORS
 
+template <typename T, typename Predicate>
+qsizetype erase_if(QSet<T> &set, Predicate pred)
+{
+    return QtPrivate::qset_erase_if(set, pred);
+}
+
 QT_END_NAMESPACE
 
 #endif // QSET_H

src/corelib/tools/qset.qdoc

@@ -896,3 +896,12 @@
     The hash value is independent of the order of elements in \a key, that is, sets
     that contain the same elements hash to the same value.
 */
+
+/*! \fn template <class T, class Predicate> qsizetype erase_if(QSet<T> &set, Predicate pred)
+    \relates QSet
+    \since 6.1
+
+    Removes all elements for which the predicate \a pred returns true
+    from the set \a set. Returns the number of elements removed, if
+    any.
+*/